Laminated packaging material comprising barrier layer and packaging containers made therefrom

Abstract

Laminated packaging material (10a) for packaging liquid or semi-liquid food products, comprising:-a body layer (11) comprising a cellulose-based material, preferably paper or paperboard; -a first outermost liquid-tight, heat-sealable thermoplastic layer (12) arranged outside the body layer so as to constitute the outside of a package formed from a packaging material; -a second, innermost, liquid-tight, heat-sealable thermoplastic layer (13) arranged inside the body layer in direct contact with the filled food product; and-a barrier layer (14) comprising a barrier substrate layer (14b) coated with a physical vapor deposition (PVD) barrier coating comprising partially oxidized aluminum, said barrier coating having a thickness of 8 to 40 nm and a transmittance of 20 to 60%, said barrier layer being laminated between the body layer and the second innermost liquid-tight, heat-sealable thermoplastic layer.

Description

Technical Field

[0001] The present invention relates to laminated packaging materials.

[0002] Furthermore, the invention relates to a method for producing a laminated packaging material, to a packaging container comprising the laminated packaging material and to a method for producing a packaging container. Background Art

[0003] Disposable packaging containers for liquid foods are usually made of packaging laminates based on paperboard or cardboard. A common packaging container is Tetra Brik The packaging containers are sold under the trademark PTFE and are mainly used for aseptic packaging of liquid foods (e.g. milk, juice, etc.) for long-term storage at room temperature. The packaging material in such known packaging containers is usually a laminate, which comprises a bulk layer or core layer of paper or paperboard and an outer liquid-tight layer of thermoplastic. In order to make the packaging container gas-tight, in particular oxygen-tight, such as for aseptic packaging and packaging of milk or juice, the laminate in these packaging containers usually comprises at least one additional layer, most often an aluminum foil.

[0004] On the inner side of the laminate (i.e. the side of the container made of the laminate facing the filled food content), there is an innermost layer, applied on the aluminum foil, which innermost layer, the inner side layer, can be composed of one or more partial layers, which contain a heat-sealable thermoplastic polymer (e.g. an adhesive polymer and / or a polyolefin). In addition, on the outer side of the body layer, there is an outermost heat-sealable polymer layer.

[0005] The packaging containers are usually produced by modern high-speed packaging machines which form, fill and seal packages from a web or preformed blanks of packaging material. Thus, the packaging containers can be produced by reforming a web of laminated packaging material into a tube, the two longitudinal edges of which are connected to each other in a lap joint by welding together the innermost and outermost heat-sealable thermoplastic polymer layers. The tube is filled with the desired liquid food and then divided into individual packages by repeatedly sealing the tube transversely at predetermined distances below the level of the contents in the tube. The packages are separated from the tube by cuts along the transverse seals and formed into the desired geometric shape, usually a parallelepiped, by folding along prepared crease lines in the packaging material.

[0006] The main advantage of this continuous tube forming, filling and sealing packaging process concept is that the web can be sterilized continuously before tube forming, thus providing the possibility of an aseptic packaging process, i.e. a process in which the liquid contents to be filled as well as the packaging material itself are germ-reduced and the filled packaging containers are produced under clean conditions, so that the filled packages can be stored for long periods of time even at ambient temperature without the risk of microbial growth in the filled product. As mentioned above, Tetra Another important advantage of the type packaging method is that it can be packaged continuously at high speed, which has a considerable impact on cost efficiency.

[0007] Packaging containers for sensitive liquid foods, such as milk or juice, can also be produced from sheet blanks or preformed blanks of the laminated packaging material of the invention. Starting from a tubular blank of a packaging laminate folded into a flat shape, the package is first produced by assembling the blank into an open tubular container capsule, and closing one open end of the container capsule by folding and heat-sealing an integral end plate. The container capsule thus closed is filled with the relevant food (e.g. juice) through its open end, and the open end is then closed by further folding and heat-sealing the corresponding integral end plate. An example of a packaging container made from sheet and tubular blanks is the conventional so-called gable top package. This type of package also has a molded top and / or a screw cap made of plastic.

[0008] A layer of aluminum foil (also known as Alufoil) in packaging laminates provides gas barrier properties far superior to most polymeric gas barrier materials. Traditional aluminum foil-based packaging laminates for aseptic packaging of liquid foods remain the most cost-effective packaging material at this performance level on the market today.

[0009] Any other material competing with aluminum foil-based materials must be cost-effective in terms of raw materials, have at least comparable food preservation properties, and perform comparably well when converted into finished packaging laminates.

[0010] In the process of developing non-aluminum foil materials for liquid food carton packaging, it is hoped to develop prefabricated films or sheets with high barrier functions and multiple barrier functions (i.e., not only oxygen and gas barrier properties, but also water vapor, chemical substances and / or aromatic substances barrier properties) to replace traditional aluminum foil barrier materials, and adapt these films or sheets to traditional aluminum foil lamination and manufacturing processes. Such films or sheets can be coated with barrier coatings, such as by vapor deposition coatings.

[0011] Such barrier films generally have at least one disadvantage compared to conventional aluminum foil used for liquid paperboard packaging of liquid foods. An important disadvantage may be the high manufacturing cost of such barrier films and / or the complexity of their manufacturing methods. Another disadvantage may be that when converted into laminated packaging materials, it increases the complexity of the lamination process, so that a direct replacement of aluminum foil is not possible.

[0012] A vapor deposited coating usually has some barrier properties, in particular water vapor barrier properties, a so-called metallized coating, such as an aluminum physical vapor deposition (PVD) coating.

[0013] This vapor deposited layer consists mainly of aluminum metal and can be 10-30nm thick, which corresponds to less than 1% of the aluminum metal material in conventional thickness aluminum foil for packaging, i.e. 6.3μm. Although vapor deposited metal coatings require only a small amount of metal material, they provide low oxygen barrier properties and may need to be combined with another gas barrier material to provide a final laminate with sufficient barrier properties. On the other hand, they can complement another gas barrier layer and provide good water vapor barrier properties. Pure aluminum coatings have a metallic appearance, so they cannot be visually distinguished from foil-based packaging materials.

[0014] Other examples of vapor deposited coatings are aluminum oxide (AlOx, Al2O3) and silicon oxide (SiOx) coatings. Such coatings can be applied by PVD. Aluminum oxide (AlOx) coatings are transparent and have good oxygen barrier properties. However, the coating is quite brittle. For example, an AlOx coating is disclosed in the applicant's WO2009 / 112255.

[0015] Other coatings can be applied by plasma enhanced chemical vapor deposition (PECVD), in which the vapor of a compound is deposited onto the substrate in a more or less oxidizing condition. For example, a silicon oxide coating (SiOx) can alternatively be applied by a PECVD process.

[0016] EP437946 of Bowater Packaging Limited discloses a web for making microwave bags for packaging oxygen-sensitive and / or moisture-sensitive materials. The material comprises a web substrate having a coating consisting of a uniform mixture of metals and metal oxides having a low metal content so that the coated substrate is transparent to microwaves. The material is made by a reactive evaporation process in which a controlled amount of oxygen-containing gas is introduced into a stream of evaporated metal to deposit the mixture on a substrate. The material is formed into bags. In an example, the coating weight is about 0.1 g / m 2 For microwave-compatible products, the maximum final optical density of the coating is 0.25, corresponding to a minimum transmittance of 56%. Summary of the invention

[0017] According to a first aspect of the present invention, there is provided a laminated packaging material for packaging liquid or semi-liquid food, comprising: - a body layer comprising a cellulose-based material, preferably paper or paperboard, - a first outermost liquid-tight, heat-sealable thermoplastic layer, which is arranged on the outside of the body layer to constitute the outside of the package formed by the packaging material, - a second innermost liquid-tight, heat-sealable thermoplastic layer arranged on the inner side of the body layer in direct contact with the filled food product, and - A barrier layer comprising a barrier substrate layer coated with a physical vapor deposition (PVD) barrier coating, wherein the physical vapor deposition (PVD) barrier coating comprises partially oxidized aluminum, the barrier coating having a thickness of 8 to 40 nm and a transmittance of 20 to 60%, the barrier layer being laminated between the bulk layer and the second innermost liquid-tight, heat-sealable thermoplastic layer.

[0018] According to a second aspect, there is provided a method of manufacturing a laminated packaging material, the method comprising performing the following steps in any order: -Laminating the barrier layer to the inner side of the body layer, - applying a first, outermost, liquid-tight, heat-sealable thermoplastic layer to the outside of the body layer and applying a second, innermost, liquid-tight, heat-sealable thermoplastic layer to the inside of the barrier layer.

[0019] According to a third aspect, there is provided a packaging container for liquid or semi-liquid food, comprising the above-mentioned laminated packaging material.

[0020] According to a fourth aspect, there is provided a method of forming the above-mentioned packaging container, comprising the step of folding the laminated packaging material. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings, in which:

[0022] Figure 1 A schematic cross-sectional view of a laminated packaging material according to a preferred embodiment of the present invention is shown.

[0023] Figure 2 Shown for Figure 1 Schematic diagram of the PVD setup for a partially oxidized aluminum barrier coating on a barrier substrate layer of material.

[0024] Figure 3 Shown for Figure 1 Schematic diagram of a facility for plasma surface pretreatment of a barrier substrate layer of a material.

[0025] Figure 4 Schematic diagram showing the manufacturing Figure 1 Method for laminating packaging materials.

[0026] Figure 5a , 5b , 5c and 5d show the Figure 1 A typical example of a packaging container produced from laminated packaging materials.

[0027] Figure 6 The principle of how the packaging container of Figure 5 can be manufactured from a packaging laminate by a continuous roll-fed forming, filling and sealing process is shown.

[0028] Figure 7 A TEM image of an exemplary barrier coating 3a is shown.

[0029] Figure 8 The oxygen transmission rates of exemplary barrier layers are shown.

[0030] Fig. 9 The oxygen transmission rate of the barrier layer of the example after Gelbo bending is shown.

[0031] Figure 10 shows a plot of oxygen transmission rate versus strain for example barrier layers, with crack initiation strain values ​​indicated. Figure 10(a) shows a barrier layer based on BOPET, and Figure 10(b) shows a barrier layer based on MOPET.

[0032] Fig.11 Oxygen transmission rates for exemplary barrier layers and packaging laminates are shown.

[0033] Fig.12 The oxygen transmission rates of example packages are shown. DETAILED DESCRIPTION

[0034] The laminated packaging material of the present invention comprises a barrier layer, and the barrier layer comprises a barrier substrate layer and a partially oxidized aluminum barrier coating layer on the barrier substrate layer.

[0035] The barrier coating is applied to the surface of the barrier substrate layer by physical vapor deposition (PVD) reaction evaporation. The reactants are aluminum and oxygen, which are supplied to the PVD process in appropriate proportions so that the aluminum is only partially oxidized. A PVD device (also referred to herein as a plant) with a coating zone is used.

[0036] Aluminium is suitable for PVD processes where it is supplied to the coating zone by wire feeding. However, other methods of supplying aluminium, such as supplying in pans, can be used instead. This has the advantage of lower maintenance costs. This is called induction evaporation. As a further option, an electron beam gun can be used to evaporate aluminium sheets contained in a cooled crucible. High energy bombardment heats the aluminium source to the point where it melts and evaporates. Although electron beam evaporation is mainly used for ceramic coatings, it can also be used for metallisation, but maintenance and capital investment are higher.

[0037] Oxygen is supplied as a gas to the PVD process in the coating zone. Suitably, the oxygen is introduced through a nozzle.

[0038] Suitably, the aluminum is evaporated using plasma enhanced reactive evaporation in combination with oxygen. In the case of plasma enhanced reactive evaporation, the use of a mixture of oxygen and a noble gas (eg argon) may help stabilize the plasma discharge and / or increase the coating density.

[0039] The partially oxidized aluminum is between Al and Al2O3 in overall stoichiometry. Preferably, the partially oxidized aluminum comprises a ceramic-metal (cer-met) composite material of aluminum particles and Al2O3. The aluminum particles can be visible in TEM, as described in the following embodiments.

[0040] Without wishing to be bound by theory, the inventors believe that the growth of aluminum clusters into particles visible in TEM is affected not only by the ratio of aluminum to oxygen in the reactive evaporation PVD process, but also by process parameters such as coating line speed (high coating line speed is expected to result in smaller particles).

[0041] Furthermore, performing reactive evaporation in the presence of a plasma (ie, plasma-assisted reactive evaporation) may affect particle size growth by producing smaller particles.

[0042] The coating thickness is in the range of 8 (or 10) to 40 nm. Preferred coating thicknesses are above 15 nm and / or below 30 nm (more preferably below 25 nm). For low coating thicknesses, pinholes or other defects may be present, which may result in poor oxygen barrier properties. For high coating thicknesses, the coating may be brittle and thus crack when the barrier layer is subjected to mechanical treatments such as extrusion coating or folding. Such cracking may also result in poor oxygen barrier properties.

[0043] However, when the barrier substrate layer is polyolefin, the thickness of the barrier coating is preferably not more than 15 nm. This is because polyolefin is a soft polymer, and thus the barrier coating formed on the polyolefin substrate layer is particularly susceptible to cracking.

[0044] Preferably, the barrier coating has a non-metallic appearance. The coating is typically grey or brown. It has been found that coatings with final transmittance values ​​less than 20% have a metallic appearance, but this is undesirable. Coatings with transmittance values ​​above 20% do not have a metallic appearance after lamination, especially when unbleached board is used as the bulk layer. Preferably, the barrier layer has a transmittance of 25 to 60%, more preferably 30 to 60%. Transmittance values ​​above 60% are associated with poor oxygen barrier properties.

[0045] The barrier substrate layer may comprise a polymer film or a cellulose based material.

[0046] A typical thickness of the polymer film barrier substrate layer may be from 6 to 30 μm, such as from 8 to 20 μm, such as 12 μm.

[0047] The polymer film barrier substrate layer is preferably a pre-oriented film, such as a blown film or a cast oriented film. Both types of pre-made films are made by extruding a molten composition into a film sheet, which is then stretched into a relatively thin but stable film. This means that the film will not shrink or deteriorate due to changes in ambient conditions or aging. The film can be uniaxially oriented (i.e. oriented in the machine direction) or biaxially oriented in the machine direction (MD) and the transverse direction (CD).

[0048] The polymeric film barrier substrate layer is preferably a polyester or a polyolefin.

[0049] Polyethylene terephthalate (PET) is a preferred polyester. Monoaxially oriented PET (MOPET) and biaxially oriented PET (BOPET) are particularly preferred. Mitsubishi RNK 12.0 2 is an example of a suitable BOPET film having a thickness of 12 μm.

[0050] Polyethylene (PE, such as films comprising HDPE, MDPE and / or LLDPE and optionally small amounts of LDPE) and polypropylene (PP, such as BOPP) are preferred polyolefins.

[0051] The design of the film depends on its final application and its composition (polymer grade) is selected to meet certain requirements including mechanical properties, sealability, printability, coating acceptance, puncture resistance and / or tear strength.

[0052] Suitable membrane designs are likely to contain at least 3 layers (and possibly up to 5 layers) where one specific PE is provided in the core for stiffness and thermal stability, while other grades may be selected to provide enhanced coating receiving layers or sealants.

[0053] Suitable film materials include the base polymer films discussed in WO 2009 / 112255 pp. 17-19.

[0054] When the barrier substrate layer comprises a cellulose based material, it is preferably paper, for example of the type described in WO2022 / 117462. Suitably, the paper is a thin paper, for example 30-60 g / m 2 (gsm), and it may be high density, for example at least 900 kg / m 3 Suitably, the paper is pre-coated (eg with starch and / or PVOH) to provide a smooth surface.

[0055] By using ion bombardment in the surface treatment process, the surface can be activated before coating, thereby partially obtaining improved adhesion and gas barrier properties. This surface activation treatment includes corona, plasma, atmospheric plasma in the film manufacturing process, and online plasma pretreatment before the coating process. Such processes are discussed in US8048532B2, US10569515B2 and WO2020155795A1. Therefore, preferably, the surface of the barrier substrate layer to be PVD-coated has been pretreated by plasma and / or corona. Corona treatment is typically performed during film manufacturing. For plasma pretreatment, oxygen, nitrogen, argon and / or neon plasma can be used; oxygen / argon and neon / argon are examples of suitable plasma mixtures. Plasma can be triggered by alternating current or direct current. Pretreatment is particularly important for polyolefin films.

[0056] It has also been seen that similar improvements can be obtained by post-treating the base layer of the barrier coating with a plasma after the barrier coating is formed. The post-treatment may help oxidize the surface of the coating and / or remove aluminum hydroxide from the surface of the coating; otherwise, such aluminum hydroxide may result in poor adhesion to adjacent layers. Post-treatment with nitrogen mixed into the plasma gas is suitable.

[0057] Therefore, the film can be pre-treated and post-treated to ensure the best possible results in terms of OTR and adhesion. The pre-treatment and post-treatment can be the same or different. Barrier coated films can also be post-treated only, but with some similar improvements.

[0058] Pre-treatment and post-treatment of the film substrate and barrier coating surface, respectively, can be performed in the same PVD apparatus as the barrier coating itself, by using different (or the same) gas compositions in the plasma pre-zone and / or plasma post-zone. Each such zone is at a different pressure than the coating zone and is separated from the coating zone by appropriate arrangements. The plasma treatment can be performed by a magnetron plasma or an inductively coupled plasma arrangement.

[0059] Surface treatments can also be carried out in a separate plasma chamber of the device. They are very brief plasma treatments that act on the surface for only a few milliseconds.

[0060] Although the barrier coating of the barrier layer is preferably adjacent to the bulk layer, the barrier layer can be flipped over at will when laminated into the packaging material. The side of the barrier substrate layer not coated with the barrier coating can be laminated to the polyolefin layer through an intermediate adhesive layer of a primer or adhesion promoting layer to improve the adhesion between the layers in the laminate.

[0061] The laminated packaging material further comprises a first outermost liquid-tight, heat-sealable polyolefin layer and a second innermost liquid-tight, heat-sealable polyolefin layer. Suitable thermoplastics for the outermost and innermost heat-sealable liquid-tight layers are polyolefins, such as polyethylene and polypropylene homopolymers or copolymers, preferably polyethylene, more preferably polyethylene selected from the group consisting of low-density polyethylene (LDPE), linear LDPE (LLDPE), single-site catalyst metallocene polyethylene (m-LLDPE or mPE) and blends or copolymers thereof. According to a preferred embodiment, the outermost heat-sealable liquid-tight layer is LDPE, while the innermost heat-sealable liquid-tight layer is a blended composition of m-LLDPE and LDPE to achieve optimal lamination and heat-sealing properties.

[0062] The thickness of the innermost heat sealable layer may be 15 to 45 g / m 2 , for example 25 to 35 g / m 2 The thickness of the outermost heat seal layer can be 10 to 20 g / m 2 Depending on the type of polymer used as a sealant and the integrity requirements, thickness will vary. Generally speaking, up to 50% downgauging is allowed for mLLDPE compared to LDPE.

[0063] The bulk layer of cellulose-based material is usually the thickest layer or the layer containing the most material in the multilayer laminate, that is, the layer that contributes most to the mechanical properties and dimensional stability of the laminate and the packaging container folded from the laminate. Typically, the bulk layer comprises paper, paperboard or carton. The bending force of the bulk layer is suitably 320mN. The bulk layer can also be a layer that provides a larger thickness distance in the sandwich structure, which further interacts with a stabilizing surface layer with a higher Young's modulus on each side of the bulk layer to achieve sufficient mechanical properties and dimensional stability. The barrier substrate layer (especially paper) can be such a stabilizing surface layer.

[0064] The paper or paperboard body layer used in the present invention generally has a thickness of about 100 μm to about 600 μm and a surface weight of about 100-500 g / m 2 , preferably about 200-300g / m 2 and can be conventional paper or paperboard with suitable packaging qualities. For low-cost aseptic, long-term packaging of liquid foods, thinner packaging laminates with thinner paper core layers can be used. Packaging containers made from such packaging laminates are not folded and are more like pillow-shaped flexible bags, as described below in conjunction with Figure 5b Further explanation. Paper suitable for such bag packaging generally has a g / m 2 The surface weight is preferably about 70 to about 120 g / m 2 , more preferably from about 70 to about 110 g / m 2 .

[0065] The barrier layer may be bonded to the bulk layer by an intermediate adhesive, a thermoplastic polymer bonding layer or a so-called laminating layer, thereby bonding the barrier layer to the inner surface of the bulk layer (inside means the direction towards the inside of the packaging container made of the material). The bonding / laminating layer may be a polyolefin layer, or a layer of a polyethylene-based polyolefin copolymer or polyethylene blend, comprising a majority of ethylene monomer units. Preferably, the bulk layer is bonded to the barrier layer by melt extrusion laminating the bonding polymer layer between the web of the bulk layer and the web of the barrier layer, while pressing the three material layers together as they pass through the nip of the laminating rollers, thereby providing a laminated structure, i.e. by extrusion laminating the bulk layer to the barrier layer.

[0066] The same thermoplastic polyolefin-based materials listed for the outermost and innermost layers, and in particular polyethylene, may be suitable for use as an adhesive layer within the laminate, i.e. between a bulk layer (e.g., paper or paperboard) and a barrier layer. In one embodiment, the thermoplastic adhesive layer may be a polyethylene layer, such as a low density polyethylene (LDPE) layer.

[0067] The packaging container is of the type described below in connection with Figure 5. The packaging container may be manufactured partly or completely from a laminated packaging material.

[0068] The folding of the laminated packaging material and other steps of forming the packaging container involve mechanical processing of the barrier layer.

[0069] The packaging container may be formed from a laminated packaging material and partially sealed, filled with a liquid or semi-liquid food product, and then and finally completely sealed by sealing the packaging material to itself, optionally in conjunction with a plastic opening or top of the package.

[0070] Preferably, the oxygen transmission rate of the laminated packaging material is less than 5 cm 3 / m 2 / 24h / atm, more preferably less than 2cm 3 / m 2 / 24h / atm, especially when BOPET is used as the barrier substrate layer. definition

[0071] The term "long-term storage" in connection with the present invention means that the packaging container should be able to maintain the quality of the packaged food, i.e. nutritional value, hygienic safety and taste, under ambient conditions for at least 1 or 2 months (e.g. at least 3 months, preferably longer, e.g. 6 months, e.g. 12 months or longer).

[0072] The term "package integrity" generally refers to package sealing, i.e. the ability of a packaging container to resist leakage or breakage. More specifically, it defines the resistance of a package to the intrusion of microorganisms (e.g., bacteria, dirt, and other substances) that could spoil the filled food and shorten the expected shelf life of the package.

[0073] The term "liquid or semi-liquid food" generally refers to a food with a flowing content, which may optionally contain food pieces. Viscous foods are also included. Dairy products and milk, soy, rice, grain and seed beverages, juices, nectars, still drinks, energy drinks, sports drinks, coffee or tea drinks, coconut water, wine, soups, purees, jalapenos, tomatoes, sauces (e.g., pasta sauce), beans and olive oil are some non-limiting examples of food.

[0074] The term "sterile" in relation to packaging materials and packaging containers refers to a state in which microorganisms are eliminated, inactivated or killed. Examples of microorganisms are bacteria and spores. Typically, when a product is aseptically packaged in a packaging container, an aseptic process is used. In order to maintain sterility during the shelf life of the package, the integrity of the package is of course very important. In order for the filled food to have a long shelf life, it may also be important that the package has barrier properties to gases and vapors (e.g. oxygen) in order to preserve its original taste and nutritional value, such as its vitamin C content. Measurement method Transmission Electronic Microscopy (TEM) and Thickness

[0075] The thickness of the barrier layers was measured by Transmission Electronic Microscopy using a Titan 80-300, FEI equipment. The samples were prepared by ultrathin sectioning on an EMUC6 Microtome (microtome) from Leica. Each barrier layer was embedded in an epoxy resin (EpoFix-Struers) which polymerized within a few hours at room temperature. The resin blocks were transversely sectioned by ultrathin sectioning using a diamond knife (60 nm thick sections) at room temperature. TEM images were taken at 300 kV using a contrast film (40 μm). The thickness of the barrier coating was measured using DigitalMicrograph software. Oxygen Transmission Rate

[0076] OTR is the amount of oxygen that passes through a material's surface area per unit time at a given temperature and relative humidity, a given atmospheric pressure, and a given oxygen partial pressure.

[0077] The OTR on the barrier layer was measured in a 100% oxygen atmosphere (1 atm oxygen) according to ASTM D3985-05. The OTR on the laminate was measured in a 20% oxygen atmosphere (0.2 atm oxygen, i.e., in air) according to ASTM F1927-14. The OTR on the package was measured at 20% oxygen using an Oxtran 2 / 21 device based on a coulometer sensor according to ASTM F1927-14 and ASTM F1307-14. The measurements were performed on flat samples and packages in accordance with ASTM F1927-14 under controlled climate conditions. All OTR measurements were performed under 23°C and 50% relative humidity (RH) climate conditions. Crack Onset Strain

[0078] The crack initiation strain of the barrier layer is determined by measuring the OTR under strain. This is done at 23°C and 50% RH using a combination of the OTR measurement method of ASTM D3985 (described above) and the tensile properties of plastic sheets measurement method of ASTM D882. The OTR is measured with the barrier layer under a constant strain that is gradually increased (e.g., 0.1%) with no relaxation between measurements. The smaller the step size, the more accurate the measurement. At a certain strain value, the OTR increases significantly, indicating that a crack has occurred in the barrier coating. This is the crack initiation strain. Transmittance

[0079] Optical density is measured during production by a densitometer, i.e. an instrument using the diffuse light transmission principle (e.g. Macbeth, Tobias or similar instruments). This instrument is suitable for measuring the optical density values ​​of coated films. The measurement accuracy and precision of aluminum coated films can be very high, approximately + / -0.2 OD and + / -0.01 OD respectively within the measuring range of 0 to 6.60 OD.

[0080] In laboratory measurements, a spectrophotometer can alternatively measure transmittance across the entire visible spectrum (380-800nm). The optical density is calculated from the transmittance (T) value at 560nm according to the OD formula below, and the resulting value is as accurate and comparable to the transmission densitometer value.

[0081] The relationship between transmittance and optical density is as follows: T=10 -OD %T = 1100 x T OD=-logT OD = optical density T = Transmittance

[0082] The transmittance T is defined as I1 / I0, where I1 = transmitted light ("output") and I0 = incident light ("input"). Therefore, OD = -log 10 (I1 / I0)

[0083] Unless otherwise stated, the transmittance values ​​relate to the final values ​​after the barrier coating has stabilized in air. In the examples, the transmittance values ​​of the barrier coating were measured online during the coating process. Gelbo Flexing

[0084] Gelbo bending is performed according to ASTM F392. The bending action involves twisting and horizontal movement (compression), repeatedly twisting and crushing the membrane. X-Ray Photoelectron Spectroscopy (XPS)

[0085] XPS analysis of the barrier layer was performed using NOVA-KRATOS, and the analysis conditions were as follows:

[0086] X-ray source: monochromatic Al Kα 225W for full spectrum (Survey) and elemental spectrum Analysis area: 300 x 700 μm 2 , grazing detection Detection angle: Normal detection (θ=0°) Analysis depth: less than 10nm DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0087] Figure 1 1 shows a laminated packaging material (also referred to herein as packaging laminate) for liquid carton packaging 10a according to a preferred embodiment of the present invention, wherein the laminate comprises a paperboard body layer 11 and a liquid-tight and heat-sealable polyolefin layer 12 applied to the outside of the body layer 11, the side facing the outside of the packaging container made of the packaging laminate. The polyolefin of the outer layer 12 is a conventional low-density polyethylene (LDPE) of heat sealability. The innermost liquid-tight and heat-sealable layer 13 is arranged on the opposite side of the body layer 11, i.e., the layer 13 will be in direct contact with the packaged product. Therefore, the innermost heat-sealable layer 13 comprises m-LLDPE, which is used to form a very strong seal of the liquid packaging container made of the laminated packaging material.

[0088] The bulk layer 11 is laminated to a barrier layer 14 (also referred to herein as a barrier film), which is formed of an oriented BOPET film barrier substrate layer 14b coated with a PVD barrier coating 14a comprising partially oxidized aluminum. The coating 14a is applied by PVD reactive evaporation to a thickness of approximately 15 nm. The form of partially oxidized aluminum will be discussed in more detail in the examples below.

[0089] Figure 2 Schematic diagram of an example of a facility 20a for PVD forming a coating 14a on a polymer film barrier substrate layer 14b; 24b-c. On the coating receiving side, the film substrate 14b; 24b-c is subjected to continuous evaporative deposition to form the coated barrier layer 14 of the present invention. Aluminum vapor comes from a solid aluminum evaporation source 21. Aluminum evaporation is thermal evaporation, which occurs when an aluminum wire contacts a high temperature surface (Joule heating to 1500-1700°C) containing boron nitride.

[0090] A limited amount of oxygen is introduced into the chamber through a nozzle. Reactive evaporation occurs between the aluminum and the oxygen.

[0091] Prior to commencing the PVD coating operation, the surface of the polymer film barrier substrate layer 14b is briefly pre-treated by plasma to functionalize and clean the surface, thereby making the surface more amenable to coating and creating better adhesion between the coating and the substrate.

[0092] Figure 3 Schematic diagram of a facility for plasma surface pretreatment of a polymer film barrier substrate layer. The film substrate 44 is subjected to oxygen-argon plasma on one surface thereof, and in a plasma reaction zone 50 formed in the space between a magnetron electrode 45 and a cooled film transport roller 46 (also used as an electrode), as the film moves forward by the rotating roller, it passes through the plasma reaction zone along the circumferential surface of the roller. The plasma is used only for surface treatment.

[0093] The post-treatment is also used to remove aluminum hydroxide and oxidize the surface of the coating 14a.

[0094] Back to Figure 1 In the structure shown, the first outer side of the barrier layer 14 is laminated to the body layer 11 through the LDPE intermediate adhesive layer 15. The innermost heat sealable layer 13 comprising m-LLDPE is adhered to the barrier layer 14 through the LDPE layer 16 and an optional adhesive polymer (e.g., a polyolefin having functional polar groups) to enhance adhesion to adjacent layers.

[0095] exist Figure 4 The method for making Figure 1 The lamination process 30 of the laminated packaging material 10a of the present invention is shown, wherein the body layer 11 is laminated to the barrier layer 14 by extruding an intermediate adhesive layer of LDPE 15; 34 from an extrusion station 35 and pressing together in a roller gap 36. The barrier layer 14 has a pre-applied barrier coating 14a on one side of the substrate layer as described above, and this side faces the body layer 11, as shown in FIG. Figure 1As shown. Thus, the laminated paper body layer and barrier layer pass through a second extruder feed block 37-2 and a lamination nip 37, where the outermost heat-sealable LDPE 12; 37-3 layer is coated onto the outer side of the paper layer. Furthermore, the laminate comprising the outermost heat-sealable polymer layer 12; 37-3, passes through a third extruder feed block 38-2 and a lamination nip 38, where the innermost heat-sealable polymer layer 13; 38-3 is coated onto the barrier layer side of the paper film laminate forwarded from 37. As an alternative, the latter step may advantageously be performed before the lamination at 37, in order to protect the barrier layer 14 on the inside as quickly as possible, and according to a separate alternative embodiment, the outermost layer may even be laminated to the paperboard at 37 before the lamination at 36. The finished packaging laminate 39 is finally wound onto a storage reel (not shown).

[0096] Figure 5a An embodiment of a packaging container (also referred to herein as a package) 50a produced by a packaging laminate 10a according to the present invention is shown. The packaging container is particularly suitable for beverages, sauces, soups, etc. Typically, the volume of such a package is about 100 to 1000 mL. The packaging container can be of any shape, but is preferably brick-shaped, with longitudinal and transverse seals 51a and 52a, respectively, and an optional opening device 53. In another embodiment (not shown), the packaging container can be formed into a wedge shape. In order to obtain this "wedge shape", only the bottom of the package is folded into shape so that the transverse heat seal at the bottom is hidden under the triangular wing, which is folded and sealed to the bottom of the package. The top transverse seal remains unfolded. In this way, when the semi-folded packaging container is placed on a shelf or table in a food store, etc., it is still easy to pick up and dimensionally stable.

[0097] Figure 5b An alternative, preferred example of a packaging container 50b made from an alternative packaging laminate according to the present invention is shown. The alternative packaging laminate is thinner due to the thinner paper body layer, so its dimensional stability is not sufficient to form a parallelepiped or wedge-shaped packaging container and is not folded into shape after the transverse seal 52b. Therefore, it will remain a pillow-shaped bag-like container and be distributed and sold in this form.

[0098] Figure 5c Shown is a gable top package 50c, which is folded from a pre-cut sheet or blank, formed from a laminated packaging material comprising a paperboard body layer and a durable barrier layer of the present invention. Alternatively, a flat top package may be formed from a similar material blank.

[0099] Figure 5dA bottle-like package 50d is shown which is a combination of a sleeve 54 formed from a pre-cut blank of the laminated packaging material of the present invention and a top 55 made of injection-moulded plastic combined with an opening device such as a screw cap. This type of packaging is available, for example, in Tetra and Tetra These particular packages are formed by attaching a molded top 55 with an opening device in a closed position, which is then attached to a tubular sleeve 54 of laminated packaging material, the bottle-top capsule thus formed is sterilized, filled with the food product, and finally folded to form the bottom of the package and sealed.

[0100] Figure 6 The form-fill-seal principle described in this application is shown, i.e. a web of packaging material is connected to each other in a lap joint 63 by the longitudinal edges 62 of the web to form a tube 61. The tube is filled (at 64) with the desired liquid food product and divided into individual packages by repeatedly sealing the tube transversely 65 at predetermined distances below the height of the tube filled with the contents. The packages 66 are separated by cuts in the transverse seals and formed into the desired geometry by folding along prepared crease lines in the material. Example

[0101] A series of barrier layers 14 are produced by vapour coating a barrier substrate layer 14b. The barrier layers are included in a packaging laminate which is then formed into a package as described below.

[0102] The barrier substrate layers were BOPET (Mitsubishi primer film, BOPET RNK12-2DF) and MOPET (in-house developed) polymer films.

[0103] like Figure 3 As shown, the barrier substrate layer was plasma pre-treated. Direct current was used.

[0104] The partially oxidized aluminum barrier coating 14a is applied by PVD, where a reaction between aluminum and oxygen vaporizes, such as Figure 2 As shown. The film substrate web was 1900 mm wide and was coated at a reference speed of 7.8 m / s. Oxygen was injected into the evaporation zone at different flow rates to provide an atmosphere consisting of different ratios of evaporated oxygen and aluminum. The test coating was formed using a lower oxygen to aluminum ratio than the control coating.

[0105] The amounts of oxygen and aluminum were varied as shown in Table 1 ("sccm" = standard cubic centimeter gas volume flow): Table 1

[0106] The barrier layer is used to make packaging laminates. The laminate structure is as above Figure 1 As shown, the laminate is Figure 4 All laminates produced therefore have the same general structure, are made from the same polymer and paperboard materials (unless otherwise stated) and are laminated to each other in the same manner:

[0107] / Outermost LDPE(12g / m 2 ) / unbleached paperboard / optional LDPE with adhesive (20g / m 2 ) / barrier coating / MOPET or BOPET film substrate with a thickness of 12μm / [LDPE (12g / m 2 ) / m-LLDPE(13g / m 2 ) or adhesive (6g / m 2 ) / m-LLDPE(19g / m 2 )] /

[0108] The laminates were formed into cuboid packages using a TETRA PAK A3 Flex / TBA1000 packaging unit with ultrasonic sealing.

[0109] Barrier layers, laminates and packaging were evaluated. TEM images

[0110] TEM images of the barrier coatings were obtained. As shown in Table 1, dark particles were visible in some coatings, but not in all coatings. Figure 7 For coating 3b, a granular structure was visible in TEM. For control coatings 1a and 1b and coating 2a, no dark particles were seen.

[0111] The inventors do not wish to be bound by this theory, they believe that the dark particles are aluminum metal particles dispersed in aluminum oxide Al2O3, so the coating is a ceramic-metal (cer-met) composite material. It is believed that when the amount of aluminum metal is small, the particles may be present, but too small to be seen by TEM. XPS analysis

[0112] XPS analysis of the three MOPET-based samples 1b, 2b, and 3b showed that the surface composition of the barrier layer coating was Al2O3. thickness

[0113] The thickness of the coating was determined by TEM and is shown in Table 1. The coating thickness ranged from 10.3 to 28.9 nm. Transmittance value of coating

[0114] The transmittance values ​​of the coatings were measured online during the coating formation process, as shown in Table 1.

[0115] The increase in transmittance values ​​after coating is believed to be due to further oxidation and stabilization of the coating during post-treatment and in air thereafter. An increase of 5 to 7 percentage points is typical (or 30-40% of the initial value when the initial transmittance is lower). Therefore, the values ​​provided in Table 1 are increased to the final stable values, which are 5-7 percentage points higher for each coating. Oxygen transmission rate of barrier layer

[0116] Figure 8 The OTR of the barrier layer at 23°C and 50% RH is shown.

[0117] It can be seen that as the oxygen ratio of the coating decreases, the OTR decreases, i.e., the OTR of the BOPET based barrier layer is 1a (control, labeled "BOPET AlOx (Standard)")>2a>>3a>4a, while the OTR of the MOPET based barrier layer is 1b (control, labeled "MOPET AlOx (Standard)")>2b>3b. A low OTR is ideal.

[0118] Coatings 3a, 4a, 2b and 3b provide OTR less than 3 cm 3 / (m 2 .24 h.1atm), which is ideal. For coatings 2b and 3b (on MOPET), the OTR is less than 2cm 3 / (m 2 .24 h.1atm), which is more ideal.

[0119] Fig. 9 The OTR of the barrier layer at 23°C and 50% RH after 0, 10 and 50 Gelbo bending cycles is shown. It can be seen that the partially oxidized aluminum coating still maintains good initial OTR performance after Gelbo bending. This shows that the mechanical properties of the coating are better than the standard AlOx control and it is less brittle. Coating 4a is thicker and has less embedded aluminum (25% transmittance compared to 18%), which makes the coating more brittle. Crack initiation strain

[0120] Figure 10 shows the crack initiation strain of (a) BOPET-based barrier layer and (b) MOPET-based barrier layer. The crack initiation strain is the strain at which the OTR (at 23°C and 50% RH) starts to increase rapidly. A high crack initiation strain indicates good mechanical properties and good crack resistance.

[0121] For BOPET based barrier layers, the crack initiation strain increases in the order 1a (control, labeled A1) < 2a (A2) < 3a (A3) < 4a (A4). For MOPET based films, films 2b (A2) and 3b (A3) also perform better than the control (1b / A1). Oxygen Transmission Rate of Laminates

[0122] Fig.11 The OTR (at 23°C and 50% RH) of a BOPET based laminate ("packaging material") is shown.

[0123] Likewise, it can be seen that as the oxygen ratio of the coating decreases, the OTR decreases, with the control 1a (labeled "BOPET AlOx (Standard)") having a higher OTR than 4a.

[0124] It can also be seen that the OTR of the 4a packaging material is similar to that of the barrier layer, indicating that the barrier layer maintains good performance even after extrusion lamination. Oxygen Transmission Rate of Packaging

[0125] Fig.12 The OTR (at 23°C and 50% RH) of a package formed from the laminate ("packaging material") is shown.

[0126] Likewise, it can be seen that as the oxygen ratio of the coating decreases, the OTR decreases. For both MOPET and BOPET, the OTR of the standard AlOx coating is higher than that of the modified AlOx coating. Appearance

[0127] The appearance of the test coatings was assessed visually. The coatings were generally gray, brown, dark brown, or blue, but in one case the coating was purple.

[0128] It was found that coatings with final transmittance values ​​less than 20% had a metallic appearance. Coatings with transmittance values ​​above 20% did not have a metallic appearance after lamination, especially when unbleached board was used.

[0129] Without wishing to be bound by theory, the inventors believe that the appearance of the coating depends on the thickness of the coating and the size of the aluminum particles. Example Conclusion

[0130] The coatings in the examples have several advantages. -The coating has a non-metallic appearance, especially after lamination, so it can be visually distinguished from metal and metallized films. This can be important to meet market demands. For example, the Japanese market requires a barrier layer that has a non-metallic appearance to enable packaging recycling. -The coating provides effective barrier properties, as shown by the OTR. Good OTR is maintained when the barrier layer is converted into a laminate (including extrusion coating) and when the laminate is formed into a package. Good OTR is also maintained after the Gelbo bend test. The crack initiation strain is high. Therefore, the coating exhibits better mechanical properties than traditional AlOx coatings, which tend to be brittle. Again, without wishing to be bound by theory, the inventors believe that the ceramic pad structure with aluminum particles contributes to the good mechanical properties of the test coating by reducing brittleness. The coating is expected to be used as a barrier layer for liquid packaging laminates (including laminates for long-term sterile, room temperature storage), where crack resistance is very important. Low coating thickness helps to obtain good mechanical properties: thicker coatings used in the prior art, such as the coatings of EP437946 (about 5-7 times the thickness of the example) may be more brittle. - The coatings can be applied at higher coating speeds than PECVD coatings using standard PVD equipment. Likewise, the low coating thicknesses allow for higher coating speeds. Therefore, these coatings offer a low-cost, scalable option. - The coating uses a lower amount of metal than conventional aluminum foil, which also makes the laminate easier to recycle and produces less CO2 during manufacturing. In addition, the PE used in the layers may be bio-based. Therefore, the example laminate has sustainability advantages. -The coating is microwaveable.

[0131] Finally, it is to be noted that the invention is not limited to the embodiments shown and described above, but may be varied within the scope of the claims.

Claims

1. A laminated packaging material (10a) for packaging liquid or semi-liquid food, comprising: - a body layer (11) comprising a cellulose-based material, preferably paper or paperboard, - a first outermost liquid-tight, heat-sealable thermoplastic layer (12) arranged on the outside of said body layer to constitute the outside of a package formed by said packaging material, - a second innermost liquid-tight, heat-sealable thermoplastic layer (13) arranged on the inner side of said body layer so as to be in direct contact with said food filled therein, and - a barrier layer (14) comprising a barrier substrate layer (14b) coated with a physical vapor deposition (PVD) barrier coating, the physical vapor deposition (PVD) barrier coating comprising partially oxidized aluminum, the barrier coating having a thickness of 8 to 40 nm and a transmittance of 20 to 60% measured by a spectrophotometer at wavelengths in the visible spectrum, and after stabilization of the coating in air, the barrier layer is laminated between the bulk layer and the second innermost liquid-tight, heat-sealable thermoplastic layer.

2. The laminated packaging material according to claim 1, wherein the partially oxidized aluminum comprises a ceramic-metal composite material of aluminum particles and Al2O3.

3. The laminated packaging material according to claim 1 or 2, wherein the barrier coating has a non-metallic appearance.

4. The laminate packaging material according to any one of the preceding claims, wherein the barrier substrate layer comprises a polymer film or a cellulose-based material. 5 . The laminated packaging material according to claim 4 , wherein the polymer film is a polyolefin film or a polyester film.

6. The laminated packaging material according to claim 5, wherein the polymer film is a pre-made uniaxially or biaxially oriented film.

7. The laminated packaging material according to claim 6, wherein the polymer film is a uniaxially oriented polyethylene terephthalate (MOPET) film or a biaxially oriented polyethylene terephthalate (BOPET) film.

8. The laminated packaging material according to claim 4, wherein the barrier substrate layer is a paper layer.

9. Laminated packaging material according to any of the preceding claims, wherein the surface of the barrier substrate layer to be PVD coated has been pretreated during film manufacturing by in-line plasma pretreatment and / or corona, flame or atmospheric plasma.

10. The laminated packaging material according to any of the preceding claims, wherein the barrier coating has been post-treated by plasma treatment.

11. A laminated packaging material according to any one of the preceding claims, wherein the PVD barrier coating has been applied by plasma assisted reactive evaporation.

12. A method for producing a laminated packaging material according to any one of claims 1 to 11, comprising the following steps in any order: - laminating the barrier layer to the inner side of the body layer (11), - applying said first outermost liquid-tight, heat-sealable thermoplastic layer (12) to said outer side of said body layer and applying said second innermost liquid-tight, heat-sealable thermoplastic layer (13) to said inner side of said barrier layer (14).

13. A method according to claim 12, wherein the barrier layer is laminated to the bulk layer by melt (co)extruding (35) an intermediate lamination layer (15) of a thermoplastic polymer between the bulk layer and the barrier layer and then applying pressure in the nip of laminating rollers.

14. A packaging container (50a; 50b; 50c; 50d) for liquid or semi-liquid food, comprising the laminated packaging material (10a) as defined in any one of claims 1 to 11.

15. A method of forming a packaging container (50a; 50b; 50c; 50d) according to claim 14, comprising the step of folding the laminated packaging material (10a).

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