BR112019024880B1 - PACKAGING LAMINATE, METHOD FOR MANUFACTURING A PACKAGING LAMINATE, AND PACKAGING CONTAINER - Google Patents

Abstract

The present invention relates to a laminated liquid food packaging material comprising a volumetric layer and a barrier layer portion and a polymer layer structure to balance package integrity versus package openability. The invention further relates to the manufacturing method of the laminated packaging material and to a packaging container for packaging liquid food, comprising the laminated packaging material.

Description

technical field

[001] The present invention relates to a laminated packaging material for liquid packaging with a barrier layer or a barrier coating that is sensitive to strain cracking, and to a method for manufacturing the laminated packaging material.

[002] Furthermore, the invention relates to packaging containers comprising laminated packaging material or made from laminated packaging material.

Fundamentals

[003] Single-use disposable packaging containers for liquid foods are often produced from a cardboard or paperboard-based packaging laminate. One of these common packaging containers is marketed under the trademark Tetra Brik Aseptic® and is primarily used for aseptic packaging of liquid foods such as milk, fruit juices, etc., sold for long-term ambient storage. The packing material in such a known packing container is typically a laminate comprising a volumetric layer of paper or paperboard and outer layers of liquid-tight thermoplastics. In order to make the packaging container gas-tight, in particular oxygen-proof, for example for the purpose of aseptic packaging and packaging of milk or fruit juice, the laminate in such packaging containers normally comprises at least one additional layer, more usually an aluminum foil.

[004] Inside the laminate, that is, the side intended to have contact with the food content of a container produced from the laminate, there is an innermost layer, applied over the aluminum foil, whose innermost layer can be composed of one or several parts of layers, comprising heat-sealable thermoplastic polymers, such as adhesive polymers and/or polyolefins. Also on the outside of the bulk layer is an outermost heat sealable polymer layer.

[005] Packaging containers are generally produced using modern, high-speed packaging machines of the type that form, fill and seal packages from a continuous sheet or prefabricated raw pieces of packaging material. Packing containers can thus be produced by reforming a continuous sheet of laminated packaging material into a tube, by both longitudinal edges of the web being joined together at an overlapping joint by welding the heat sealable thermoplastic polymer layers together. internal and external. The tube is filled with the intended liquid food product and then divided into individual packages by repeatedly transversely sealing the tube at a predetermined distance from each other below the level of the contents of the tube. The packages are separated from the tube by incisions along the transverse seals and given the desired geometric configuration, usually parallelepiped or cuboidal, by forming folds along crease lines prepared in the packaging material.

[006] The main advantage of this concept of continuous packaging method for forming, filling and sealing tubes is that the continuous sheet can be continuously sterilized just before forming tubes, thus providing the possibility of an aseptic packaging method, i.e. , a method in which the liquid contents to be filled, as well as the packaging material itself, have reduced bacteria and the filled packaging container is produced under clean conditions, so that the filled packaging can be stored for a long period of time. time, even at room temperature, without the risk of microorganism growth in the filled product. Another important advantage of the Tetra Brik® type packing method is, as stated above, the possibility of continuous high-speed packing, which has a considerable impact on cost efficiency.

[007] Typically, thousands of packages can be prepared per hour. For example, the Tetra Pak® A3 speed can manufacture around 15,000 packs per hour (family size packing containers 0.9 liters and above) and around 24,000 packing containers per hour (serving packs).

[008] Packing containers for sensitive liquid food, for example, milk or juice, can also be produced from sheet-like blanks or prefabricated blanks of the laminated packaging material of the invention. From a tubular blank of the packaging laminate which is folded flat, packages are produced by first of all constructing the blank to form an open tubular container capsule, of which one open end is closed by means of folding and heat sealing of integral end panels. The container capsule thus closed is filled with the food product in question, for example juice, through its open end, which is subsequently closed by means of further folding and heat sealing of the corresponding integral end panels. An example of a packaging container produced from tubular and sheet-like blanks is the so-called conventional gable-top package. There are also packages of this type with molded lid and/or plastic screw cap.

[009] The known packaging laminate is conventionally produced from a continuous sheet of paper or paperboard which is unwound from a storage reel, while at the same time an aluminum web is unwound from a corresponding storage reel. The two unrolled webs are joined together and guided through the gap between two adjacent rotating rollers, while at the same time a laminating material, usually low-density polyethylene (LDPE), is extruded onto a fused polymer film or curtain. of polymer, which is thus applied between the webs to permanently bond the aluminum web to the paper or paperboard web. The continuous sheet of paper or paperboard is then provided on both sides with liquid-tight polyethylene liners, typically low-density polyethylene (LDPE), and then wound onto finished wrapping reels for onward transport and handling.

[0010] To improve the heat-sealing properties and quality of liquid food packaging, developments have been made to use metallocene-catalyzed linear low-density polyethylenes (mLLDPE) in the innermost heat-sealing layers. mLLDPE polymers were difficult to melt process in extrusion and molding operations, so developments in the manufacture of packaging laminates were made to blend them with other polymers, typically LDPE polymers.

[0011] WO98/26994 describes a similar packing material structure, in which the innermost heat sealable layer is a mixture of mLLDPE and from 10 to 50% by weight of LDPE. The layer that laminates the paperboard to the aluminum barrier sheet can be LDPE, mLLDPE or a mixture thereof. If a mixture is used in the lamination layer, a lower amount of 10 to 20 g/m2 is recommended in WO98/26994. This development failed, however, and was never continued. It was more difficult to find the appropriate mixes than expected at the time.

[0012] EP1164085B1 was a patent filed and subsequently granted that describes a similar laminated packaging material with an innermost hot-curable layer comprising a metallocene-catalyzed linear low-density polyethylene (mLLDPE), with a mixture of mLLDPE and a low density polyethylene (LDPE), whose blending material has a density of 0.900 to 0.915 kg/dm3, a maximum melting temperature of 88 to 103°C, a melt index of 5 to 20 g/10 min and a dilation of 1.4 to 1.6, the thickness of the innermost layer being 20 to 50 µm. The same polymer blend can be used in the outermost layer on the outside of the cardboard, as well as the laminate layer that is laminating the cardboard and a barrier layer of aluminum foil.

[0013] In practice, in commercial packaging laminates of these types, the mixed mLLDPE component was used only for the innermost heat sealable layer, however, while for the lamination layer, i.e. the layer between the paperboard and aluminum foil, and for outer layers, LDPEs continued to be used. It was understood that polymers containing mLLDPE are stronger and more resistant, because they impart very high tenacity to a packaging laminate, so that the laminated material becomes difficult to tear along a perforation line or with an opening device. , or difficult to penetrate with a straw through a straw hole, when comprising several such layers of mixture.

[0014] In EP1507660B1, a heat sealable polymer layer configuration is described, which is adapted to improve the opening properties of packaging laminates of the above type while maintaining good heat sealing properties and melt processing properties. This laminate is also used in practice, i.e. in commercial materials, but although some properties have been improved, it adds greater complexity in manufacturing and is connected with a higher manufacturing cost. In such laminated materials, the inner layers are, as counted from the aluminum barrier sheet, a thin layer of an adhesive polymer, a layer of LDPE and an innermost layer of a mixture of an mLLDPE and preferably 30% by weight to 40% by weight of an LDPE. For the lamination layer and the outer layer still LDPE polymers are used.

[0015] The further decrease in the costs of these packaging materials can be done by reducing the thickness of the various layers of the laminate.

[0016] However, this may lead to an increased risk that the mechanical strength and integrity of the packaging of filled and sealed containers, as well as the barrier properties of the material, will be impaired. Instead, it has been normal to increase the thicknesses of the various layers, ensuring high quality in difficult circumstances. This is slightly more expensive counted as raw material costs, but more importantly, it counteracts environmental sustainability as the polymeric materials in today's packaging laminates still largely originate from fossil raw material sources. It is undesirable to increase the amount of polymers in laminates more than necessary.

[0017] In addition, increasing the amounts and thicknesses of the polymer layers can also cause different packaging performance problems and negatively influence the shelf life, that is, the shelf life of the packaged food product.

[0018] Another aspect regarding technical performance needs to be considered, also for reasons of cost and efficiency, that is, the processability of materials in the lamination process. This refers to the melt processability of the materials in the various extrusion and rolling operations, and how many downtimes or changes may be required in the manufacturing process due to changes in polymers and extruder arrangements between different package specifications. The rolling process is usually carried out at 300 m/min or above, such as 400 m/min or above, such as 500 m/min or above, such as 600 m/min or above.

summary

[0019] It is therefore an objective to improve the current state of the art, solve at least some of the above problems and provide an improved packaging material.

[0020] In particular, it is an objective to realize an improved cardboard-based packaging laminate of the type described for packaging liquid or semi-liquid food products, which allows the manufacture of filled packages with package integrity and improved barrier properties in relation to to gas, such as oxygen, with maintained opening properties.

[0021] Another objective is to provide an improved cardboard-based packaging laminate, which allows the manufacture of filled packages with improved opening, with maintained package integrity and barrier properties for gases, such as oxygen.

[0022] A further objective is to provide an improved paperboard-based packaging laminate that allows the manufacture of filled packages with improved package integrity and barrier properties towards gas such as oxygen, as well as improved opening properties.

[0023] Another additional objective is to provide laminated packaging material with high production efficiency, that is, that it is possible to manufacture at high lamination speed.

[0024] It is yet another object to be able to provide high quality filled and sealed packaging containers from the laminated packaging material at a maintained high filling packaging speed.

[0025] Some or all of these objects are attainable according to the present invention by the laminated packaging material, the manufacturing method of the laminated packaging material, as well as the packaging container made therefrom, as defined in the appended claims.

[0026] According to a first aspect of the present invention, there is provided a packaging laminate for liquid boxes having the following laminated layer portions, a. a liquid-tight, heat-sealable outermost layer of a thermoplastic polymer, outermost meaning directed toward the outside of a packaging container made from the packaging laminate, b. a volumetric layer of carton or cardboard, the outermost liquid-tight, heat-sealable layer being applied to the outside of the volumetric layer, c. a barrier layer portion, d. a portion of the lamination layer, which connects the opposite inner side of the bulk layer to the portion of the barrier layer, e.g. a liquid-tight, heat-sealable polymer innermost layer portion applied to the opposite inner side of the barrier layer portion f. optionally, a layer of an adhesive polymer, which bonds the innermost layer portion to the barrier layer portion and has a thickness of 4 to 9 µm, the innermost layer portion with an intermediate layer of low density polyethylene (LDPE ) and an innermost layer, which constitutes the inner surface of a packaging container made from the packaging laminate, of a linear low-density polyethylene produced with a metallocene or metallocene-type catalyst (mLLDPE), the portion of the innermost layer and the adhesive polymer layer constituting the polymer layers of the packaging laminate, the portion of the lamination layer having a center layer of an mLLDPE and a backing layer of LDPE on each side of the center layer, the backing layers of LDPE bonding the core layer to the bulk layer and the barrier layer portion, on the respective sides of the core layer, the thickness of the core layer being from 4 to 15 µm and constituting not more than 40% of the total thickness of the laminating layer portion, the total thickness of the portion of the lamination layer being less than 50 µm, and the thickness of the innermost layer of mLLDPE being from 6 to 20 µm and constituting not more than 50% of the total thickness of the portion of the inner polymer layers, the total thickness of the inner polymer layers being up to 50 μm, and the innermost layer mLLDPE having at least a melting point of 95 to 105°C and the middle layer LDPE having a melting point of 105 to 115°C.

[0027] This arrangement of layers, within defined thickness and temperature ranges, provides a greater degree of freedom in improving the properties of the packaging laminate. Depending on the packaging specification (type, size, intended use, opening type, etc.), a combination of layer thicknesses within these ranges can be found that manages to improve and optimize at least one of packaging integrity/shelf life and opening and maintaining the other, as economically as possible with regard to raw material costs. In addition, this layer arrangement allows for simplified handling of the polymer layer in laminate material manufacturing line lamination operations without having to switch polymer grades and change layer configurations between different package specifications.

[0028] According to a second aspect, a method for manufacturing the packaging material of the first aspect is provided.

[0029] The method comprises a step of laminating the bulk layer onto the barrier layer portion, co-extruding the core mLLDPE layer and at least one of the LDPE backing layers of the laminating layer portion therebetween, and a separate step coating the inner layer portion into the barrier layer portion by co-extruding the innermost mLLDPE layer together with the LDPE intermediate layer and, optionally, the layer of an adhesive polymer into the barrier layer portion. By co-extruding the layers of the laminate layer portion and the inner polymer layers respectively together, the relatively thin separate layers can support each other and preserve sufficient heat together in order to ensure sufficient processability.

[0030] Alternatively, the inner layer portion and the adhesive polymer layer may be coated onto the barrier layer portion, such as aluminum foil, in a first step, in order to form a prefabricated inner portion. The portion of the barrier layer so coated is subsequently laminated to the bulk layer by melt-extruding a portion of the laminating layer in a further step.

[0031] According to a third aspect, a packaging container with correspondingly improved properties is provided from the packaging material of the first aspect.

Detailed Description

[0032] With the term “long-term storage” in connection with the present invention, it is understood that the packaging container must be able to preserve the qualities of the packaged food product, that is, nutritional value, hygienic safety and taste, under ambient conditions for at least 1 or 2 months, such as at least 3 months, preferably longer, such as 6 months, such as 12 months or more.

[0033] The term “packaging integrity” is generally understood to mean the impermeability of the package, that is, the resistance to leakage or breakage of a packaging container. It covers the package's resistance to the invasion of microbes such as bacteria, dirt and other substances that can spoil the filled food product and reduce the expected shelf life of the package.

[0034] A major contribution to the integrity of a package from a laminated packaging material is provided by good internal adhesion between adjacent layers of the laminated material. Another contribution comes from the resistance of the material to defects such as holes, ruptures and the like within each layer of the material, and yet another contribution comes from the strength of the gaskets, by which the material is sealed in forming a packaging container. With regard to the laminated packaging material itself, the property of integrity focuses primarily on the adhesion of the respective laminate layers to their adjacent layers, as well as the quality of the individual material layers. As far as packaging sealing is concerned, integrity is mainly focused on the quality of the sealing gaskets, which is guaranteed by robust and smooth sealing operations in the filling machines, which in turn are guaranteed by the heat sealing properties. suitably adapted from the laminated packaging material.

[0035] The term “liquid or semi-liquid food” generally refers to food products with a fluid content that optionally may contain pieces of food. Dairy and milk, soy, rice, grain and seed-based beverages, juice, nectar, still drinks, energy drinks, sports drinks, coffee or tea drinks, coconut water, wine, soups, jalapeno peppers, tomatoes, sauce (such as pasta sauce), beans and olive oil are some non-limiting examples of contemplated food products.

[0036] The term "aseptic" in connection with a packaging material and a packaging container refers to conditions in which microorganisms are eliminated, inactivated or killed. Examples of microorganisms are bacteria and spores. Generally, an aseptic process is used when a product is aseptically packaged in a packaging container. For continuous asepsis during the shelf life of the package, package integrity properties are obviously very important. For an extended shelf life of a filled food product, it may be important that the packaging has barrier properties against gases and vapors, such as oxygen, in order to maintain the original taste and nutritional value, such as its vitamin C content. .

[0037] The term “volumetric layer” is usually understood to be the thickest layer or the one that contains the most material in a multilayer laminate, that is, the layer that most contributes to the mechanical properties and dimensional stability of the laminate and containers laminated packaging materials, such as cardboard or paperboard. It can also mean a layer that provides a greater thickness distance in a sandwich structure, which further interacts with the stabilizing layers, which have a higher Young's modulus, on each side of the volumetric layer, in order to obtain sufficient mechanical properties. and dimensional stability.

[0038] The term “hot sealing” refers to the process of welding a surface of a thermoplastic material to another thermoplastic surface. A heat sealable material should, under appropriate conditions, such as applying sufficient heat and pressure, be capable of generating a seal when pressed against and in contact with another suitable thermoplastic material. Adequate heating can be achieved by induction heating or ultrasonic heating or by other conventional means of contact or convection heating, for example hot air or pulse heating. Upon heating, the mobility of the polymeric chains increases on the surfaces of the material intended to seal each other, so that the chains untangle and move and re-entangle with polymeric chains of the opposite sealing surface. Upon cooling, strong bonds of entangled polymer chains are created across the sealing interface, thereby bonding the two material surfaces to each other. The heat sealing operation must take place in parts of a second and the duration of the different phases, such as heating, partial melting, joining and cooling, is counted in milliseconds, in packaging machines that produce thousands of packages per hour.

[0039] The barrier materials used in laminated packaging materials that benefit from the present invention are those that are sensitive to cracking when stretched, tensioned or flexed, such as in creases, folds and shaping of laminated materials in pouches or cuboidal packaging containers from the laminated material. An example of such barrier materials is metal foil, such as conventionally used aluminum foil. However, also very thin coatings of barrier materials over a thicker substrate, a polymer film or a thin paper sheet substrate can suffer a similar vulnerability, due to their thickness per minute, which can only be counted in a few micrometers. , or less, or as in the case of vapor deposition coatings or vacuum coatings, in nanometers. Examples are metallised coatings applied by physical vapor deposition, or inorganic coatings such as silicon oxides or aluminum oxides coatings, or coatings of so-called amorphous diamond-like carbon (DLC) coatings.

[0040] Thicknesses of polymer layers are given as μm in this document. It should be understood that amounts of layered polymers can also be given in grams per square meter (g/m2). By recalculating with the density for the specific polymer, it is possible to compare these quantities and thicknesses. Polymer layer thicknesses can vary by ± 2 µm, such as ± 1 µm, due to normal fluctuations in lamination, production and measurements.

[0041] Thus, by the structure of the laminate layer described above and in the appended claims, it is possible to further improve the structures of existing materials and packages made therefrom. With respect to prior art material structures, for any size or type of package, it will be possible to further improve the integrity of the package by this new material structure and still provide the ability to open the package, or vice versa. Furthermore, it will be possible to optimize these properties without adding total cost of production to prior art material structures, which will also become evident in the following description.

[0042] Since the liquid case packaging industry began to explore the strengths and weaknesses of mLLDPE polymers, knowledge and understanding of lamination and production processes has increased. Today's laminating equipment is more advanced. In the past, it was necessary to blend mLLDPE with LDPE in order to melt extrude into a stable and reliable cast film to be applied to a fast moving continuous sheet surface. Rolling speeds are considerably higher and more demanding today than they were 20 years ago, as are filling and sealing operations on filling machines.

[0043] Still, a way has been found to apply layers consisting of, or essentially consisting of, mLLDPE.

[0044] With a so-called three-layer inner structure, i.e. the sequence of Al sheet and inside being adhesive polymer, middle layer of LDPE and innermost layer comprising mLLDPE in a blend with LDPE, it became clear that the innermost layer comprising mLLDPE should not be too thick as this may impair the package's openability. When considered insufficient for the sealing and integrity of the package, it was tried, however, to increase the amount of mLLDPE in the layer, until this layer did not consist of LDPE. In doing so, it was found that these layers of pure or substantially pure mLLDPE of maintained thickness impaired the openability of the package, but that when the thickness of the layer of pure mLLDPE, in a next step, decreased, the integrity of the package could be maintained at an improved level, while the opening ability was also improved. Thus, it was surprisingly found that by using less mLLDPE inside but a pure layer of mLLDPE, the seemingly unattainable balance between improved openability and improved package integrity could be achieved and the mechanical strength of the layers could be maintained.

[0045] An additional advantage of using only mLLDPE in the innermost layer is that mLLDPEs provide a wider “sealing window” in the packaging sealing process, i.e., greater robustness of sealing quality, regardless of temperature control of sealing in the sealing operation.

[0046] As mLLDPE starts sealing earlier, by starting melting earlier, it requires less thermal energy to be applied and therefore allows for a higher sealing speed.

[0047] The configuration of the inner layer may consist of said three layers, i.e., an adhesive polymer layer, an intermediate layer of LDPE, and an innermost heat sealable layer of mLLDPE.

[0048] In addition, the other layers of the laminated packaging material influence the integrity and openability of the package, and although an increased amount of LDPE does not influence the openability to the same extent as mLLDPE, it was understood that a layer too thick LDPE laminate also reduces opening ability.

[0049] Reducing the thickness of the LDPE laminate layer, on the other hand, was not desired, because then different integrity problems would arise, while the opening ability was a little better. Such different integrity problems may arise, for example, because fibers from the surface of the bulk paperboard layer penetrate the polymer of the laminate portion of the layer. Thus, defects in a portion of the sensitive barrier layer can be created, such as, in the worst case, small holes in the barrier material, but more often poor adhesion between the polymer of the laminate layer and the portion of the barrier layer. In the case of an aluminum foil barrier, it is important that the surface of adjacent layers is even and smooth for best wetting ability and chemical bonding.

[0050] The mLLDPE polymers have better mechanical properties, such as i.a. puncture resistance, which is of great value in the laminate layer portion. Still, an mLLDPE does not provide good enough adhesion when laminated in direct contact with, for example, aluminum foil. For optimal adhesion, it has proved necessary to laminate the mLLDPE polymer layer, for example, to aluminum foil via an interjacent LDPE layer, which can be extrusion laminated at a higher temperature such as 320 to 330 °C, and which provides good mechanically interlocking adhesion to the paper fibers on the board surface as well. Thus, the backing LDPE layers provide the best possible bond to the paperboard and barrier layer portion, while simultaneously providing a good bond to the core mLLDPE layer. Together, the three layers of the laminate layer portion also provide sufficient thermal energy for good bonding between all the laminate layers between the bulk layer and the barrier layer portion, and to reduce bottlenecking effects.

[0051] By carrying out an idea of adding a portion of the amount of mLLDPE, which was removed from the inner layer portion, to the laminate layer portion, it was possible to work towards a laminate material that had improved packaging performance (such as longer service life) and still a maintained or acceptable opening capacity.

[0052] The material layers that are important for the opening ability of a package with opening arrangements prepared in the laminated material are the polymer layers and the barrier layers. They are intact and completely cover the prepared opening arrangements, such as perforations, straw holes and opening holes, which are pre-cut into the bulk layer prior to lamination into the polymer and barrier layers. When these layers are laminated over these prepared holes or slots, they are adhered to each other as laminated membranes, polymer layers and barrier layers within the areas of the holes. On opening, it is the strength of such membranes or individual layers that most influences the opening capacity. Furthermore, the good adhesion of the layers to each other within the membrane supports the opening ability well.

[0053] There are difficulties in extrusion coating a single layer of pure or substantially pure mLLDPE, and even if the pure mLLDPE layer inside was coextrusion coated together with other melt layers, initially it was not possible, at a speed normal production. It is not possible to extrusion coat or laminate a single layer of mLLDPE, at the required speeds, i.e. above 300 m/min, such as above 400 m/min, such as above 500 m/min and preferably above 600 m/min. min. However, as the development work progressed, it was realized that when the mLLDPE layer became thin enough relative to the LDPE co-extruded polymer layers, it became easier to provide a stable and uniform layer without throttling issues. or loose edges of extruded cast curtain. Thus, by keeping the mLLDPE layer relatively thin and supported by the adjacent molten co-extruded LDPE layers, and by choosing the polymers so that they flow well on coextrusion together, it has been found that it is not necessary to mix the mLLDPE polymers with LDPE. In melt extrusion of a cast polymer film curtain for coating onto a continuous sheet of moving substrate, there are two phenomena that need to be controlled and mitigated to produce a uniform and intact coating polymer layer. On the one hand, in the case of low melt strength, there may be strangulation of the edges of the cast curtain, i.e. the edges of the cast film will become narrower than the web substrate, and the film is thicker along the edges of the sheet. film curtain. On the other hand, in the case of thin coating layers, there may be instability of the edges, so that the edges wobble along with the speed movement of the film curtain, so that the film can break easily.

[0054] These are, therefore, the difficulties in extrusion coating and lamination of mLLDPE polymers. When considering the introduction of a layer of mLLDPE layer in the laminate layer portion, additional openability and manufacturing efficiency issues were expected. However, when realizing what was needed, a configuration of LDPE and mLLDPE in three coextrusion layers was developed, which allowed the use of mLLDPE in the laminate layer portion, without having to slow down the lamination process, keeping the layer of relatively thin mLLDPE and using LDPE backing layers on each side of the mLLDPE layer.

[0055] Therefore, it was surprisingly observed that a similar amount of mLLDPE in the structure of the material as a whole, although distributed differently between the portions of the polymer layer, could considerably improve the packaging integrity and shelf life, without impairing the ability to open the package. Alternatively, it could improve openability without impairing package integrity and shelf life, or improve the two opposite properties.

[0056] The structure of the material with the ranges of layer thicknesses, as defined in the present invention, allows a good balance between the integrity and shelf life of the package, on the one hand, and the opening capacity properties, on the other hand , across the entire range of package sizes and formats. Although small packages, such as portion packs of about 0.2 to 0.3 liters, use a very thin cardboard as the bulk layer and have a lighter weight of liquid, they work well at the lower end of the layer thickness ranges. One-litre family-size cartons using stiffer, thicker cardboard can also operate at the lower end of the strips. However, there are larger carton formats and larger sizes, such as cartons of up to two liters, which require thicker and heavier cardboard to be able to support a greater weight of filled liquid and which are considerably more rigid to fold into cuboidal cartons. Such packages typically need thicker polymer layer thicknesses and therefore operate at the higher end of the layer thickness range. Furthermore, when precut aperture arrangements are quite large, such as holes with a diameter greater than 10 mm, such as greater than 15 mm, it has been observed that relatively thick and stable polymer layers are required to provide a stable membrane, but that can still be easily opened from the laminated polymer and barrier layers.

[0057] By maintaining the structure of the laminate layer above, with the defined order of layers in the laminate layer portion and the inner layer portion, it is still possible to achieve an improved balance between the openability and integrity of the package, compared to what was possible with prior art laminate layer structures.

[0058] The innermost layer and the center layer of the laminate layer portion consist, or substantially consist, of mLLDPE. The invention works at its maximum potential when there is only mLLDPE in the layers, but the essence of the invention can be worked out to some extent also by mixing the mLLDPE with a low amount of LDPE, such as up to 15% by weight, such as up to 10% by weight of LDPE. There can be different amounts of LDPE added in the layers or the same mixture can be used. By mixing, it should be understood that the beneficial effects are diluted and the good properties obtained are less prominent than using pure polymers in the layers.

[0059] Furthermore, the intermediate layer of LDPE, inside the barrier layer, can be mixed with up to 15% by weight of mLLDPE, for the same reason, that is, that the effects of the invention can be seen to a certain extent, but less than when pure LDPE is used.

[0060] The backing layers of the laminate layer portion should consist of LDPE only and should not contain mLLDPE, because they need to be extruded at a high temperature to adhere well to the bulk layer and barrier layer. In melt processing above 300°C, mLLDPE polymers may degrade and are therefore unsuitable. The co-extruded LDPE backing layers can have the same or different thicknesses, thus the laminate layer portion can have a symmetrical or asymmetrical layer structure.

[0061] The composition of the outermost layer of a thermoplastic polymer is not critical and is less important for package integrity purposes, provided it has a reasonable thickness of at least 10 μm, for heat sealing and layer integrity and quality. It may comprise mLLDPE, and the limiting factor is the overall openability of the package. Therefore, it does not seem convenient to add mLLDPE to the outer layer, because it is not necessary and may negatively influence the opening capacity of the package. However, if added and openability maintained, a correspondingly low amount of mLLDPE would appear possible to blend with an LDPE polymer while still achieving the benefits of the invention.

[0062] According to another embodiment, there may be a decorative prefabricated film laminated to the outside of the bulk layer, which is further coated with a liquid-proof and heat-sealable thermoplastic layer of a thermoplastic polymer. Such a decorative film can, for example, be a metallised film, onto which the printed decoration pattern of the package is applied by a printing operation. To preserve the openability of packaging materials provided with openable weakenings in the form of perforations or pre-cut and laminated holes in the paperboard, these pre-made films are perforated or pre-cut together with the volumetric layer once that prefabricated polymer films are often mechanically strong and difficult for the consumer to tear or open a package made from this laminated material.

[0063] Further laminated between the volumetric layer and the innermost heat sealable and liquid tight layer, there is thus a barrier layer portion comprising a barrier metal sheet or a barrier coated polymer film. A typical barrier metal sheet is aluminum foil. Alternatively, a polymer film substrate having a barrier coating, such as a dispersion-coated or liquid-film-coated barrier coating, or a vapor-deposited barrier coating can be laminated therebetween. Such barrier sheets and films have the common disadvantage that the actual barrier material is a relatively brittle or stress-sensitive material with relatively low stretchability, or is applied with a very thin and therefore sensitive coating thickness, or both. Its sensitivity to mechanical stress can increase or decrease with barrier coating thickness. During the conversion of a laminated packaging material into a packaging container, there are several operations that will apply mechanical stress to the layers of barrier material, such as creasing the material, bending and folding the material, as well as sealing it into folded and shaped packages. .

[0064] Oxygen barrier properties can be provided by thin liquid film coatings, for example barrier polymers that are coated in the form of a dispersion or solution in liquid medium or solvent, onto a substrate such as a thin film substrate. paper or polymer, and subsequently dried into thin barrier coatings. This film or liquid film coated sheet can be incorporated into the packaging laminate on the inside of the bulk layer, between the bulk layer and the innermost thermoplastic polymer layer, just as aluminum foil is known to laminate on the inside of paperboard. It is important that the dispersion or solution is homogeneous and stable to result in a uniform coating with uniform barrier properties. Examples of suitable polymers for aqueous compositions with barrier properties are polyvinyl alcohols (PVOH), water dispersible ethylene vinyl alcohols (EVOH) or water dispersible or dissolvable polymers based on polysaccharides. These dispersion-coated layers, or so-called liquid film layers (LFC), can be very thin, down to tenths of a gram per m2, and can provide high quality homogeneous layers, provided the dispersion or solution is homogeneous and stable, or that is, well prepared and mixed. PVOH has excellent oxygen barrier properties in dry conditions and also provides very good odor barrier properties, i.e. ability to prevent odorous substances from entering the packaging container from the surrounding environment, for example in a fridge or room of storage, whose capacity becomes important in the long-term storage of packages. In addition, such liquid film coated polymer layers from water-dissolvable or water-dispersible polymers generally provide good internal adhesion to adjacent layers, which contributes to good integrity of the final packaging container.

[0065] Suitably, the polymer is selected from the group consisting of polymers based on vinyl alcohol, such as water-dispersible PVOH or EVOH, polymers based on acrylic acid or methacrylic acid (PAA, PMAA), polysaccharides such as, for example, starch or starch derivatives, cellulose nanofibrils (CNF), nanocrystalline cellulose (NCC), chitosan, hemicellulose or other cellulose derivatives, water dispersible polyvinylidene chloride (PVDC) or water dispersible polyesters or combinations of two or more thereof .

[0066] More preferably, the polymer binder is selected from the group consisting of PVOH, water-dispersible EVOH, polysaccharides such as, for example, starch or starch derivatives, chitosan or other cellulose derivatives, or combinations of two or more of the same.

[0067] Such barrier polymers are thus suitably applied by means of a liquid film coating process, i.e. in the form of an aqueous or solvent-based dispersion or solution which, upon application, is spread over a layer thin and uniform on the substrate and then dried.

[0068] The liquid composition may additionally comprise inorganic particles to further improve the properties of the oxygen gas barrier.

[0069] The polymer binder material can, for example, be mixed with an inorganic compound in laminar form or formed into flakes. By layering the inorganic particles in the form of flakes, an oxygen gas molecule must migrate a longer, tortuous path through the oxygen barrier layer than the normal straight path through a barrier layer.

[0070] The inorganic laminar compound can be a nanoparticle composite called dispersed to an exfoliated state, that is, the lamellae of the layered inorganic compound are separated from each other by means of a liquid medium. Thus, the layered compound preferably can be swollen or cleaved by the polymer dispersion or solution, which in the dispersion has penetrated the layered structure of the inorganic material. It can also be swollen by a solvent before being added to the polymer solution or dispersion, or exfoliated by physical methods such as ultrasound. Thus, the inorganic laminar compound is dispersed to a delaminated state in the liquid gas barrier composition and in the dry barrier layer. There are many chemically suitable nanoclay minerals, but the preferred nanoparticles are those of montmorillonite, such as purified montmorillonite or sodium-exchanged montmorillonite (Na-MMT). The nanometer-sized inorganic laminar compound or clay mineral preferably has an aspect ratio of 50 to 5000 and a particle size of up to about 5 µm in the exfoliated state.

[0071] Preferably, the barrier layer comprises from about 1 to about 40% by weight, more preferably from about 1 to about 30% by weight, and even more preferably from about 5 to about 20% by weight , of the inorganic laminar composite based on dry coating weight. Preferably, the barrier layer includes from about 99 to about 60% by weight, more preferably from about 99 to about 70% by weight, and even more preferably from about 95 to about 80% by weight of the polymer with based on dry coating weight. An additive, such as a dispersion stabilizer or the like, may be included in the gas barrier composition, preferably in an amount not greater than about 1% by weight, based on dry coating. The total dry content of the composition is preferably 5 to 15% by weight, more preferably 7 to 12% by weight.

[0072] According to a different preferred embodiment, the inorganic particles mainly consist of laminar talc particles with an aspect ratio of 10 to 500. Preferably, the composition comprises an amount of 10 to 50% by weight, more preferably 20 to 500. 40% by weight of talc particles, based on dry weight. Below 20% by weight, there is no significant increase in gas barrier properties, while above 50% by weight, the coated layer can be more brittle and breakable because there is less internal cohesion between the particles in the layer. The polymer binder appears to be in too low an amount to surround and disperse the particles and laminate them to each other in the layer. The total dry content of this liquid barrier composition from PVOH particles and talc can be between 5 and 25% by weight.

[0073] Preferably, according to the invention, the oxygen gas barrier layer is applied in a total amount of from 0.1 to 5 g/m2, preferably from 0.5 to 3.5 g/m2, more preferably from 0.5 to 2 g/m 2 , dry weight. Below 0.1 g/m2, there will be no gas barrier properties, while above 5 g/m2, the coated layer will not bring savings to the packaging laminate, due to the high cost of barrier polymers in general and due to the high energy cost to evaporate the liquid. A recognizable level of oxygen barrier is achieved by PVOH at 0.5 g/m2 and above, and a good balance between costs and barrier properties is achieved between 0.5 and 3.5 g/m2.

[0074] According to a preferred embodiment of the invention, the oxygen gas barrier layer is applied in two consecutive steps with intermediate drying, as two partial layers. When applied as two partial layers, each layer is suitably applied in amounts of 0.1 to 2.5 g/m2, preferably 0.5 to 1 g/m2, and allows for a higher quality total layer from an amount lower than liquid gas barrier composition. More preferably, the two partial layers are applied in an amount of 0.5 to 2 g/m2 each, preferably 0.5 to 1 g/m2 each.

[0075] According to a different embodiment of the invention, barrier coatings can be applied by means of physical vapor deposition (PVD) or chemical vapor deposition (CVD) onto a substrate surface of a film material. The substrate material itself can also contribute some properties, but it must, above all, have appropriate surface properties, suitable to receive a vapor deposition coating, and must function efficiently in a vapor deposition process.

[0076] The thin layers deposited by vapor are normally only a nanometer thick, i.e., a thickness in the order of magnitude of nanometers, for example, from 1 to 500 nm (50 to 5000 Å), preferably from 1 to 200 nm , more preferably from 1 to 100 nm and even more preferably from 1 to 50 nm.

[0077] A common type of vapor deposition coating, often having some barrier properties, in particular water vapor barrier properties, are so-called metallization layers, e.g. aluminum metal physical vapor deposition coatings (PVD).

[0078] This vapor-deposited layer, consisting substantially of aluminum metal, may have a thickness of 5 to 50 nm, which corresponds to less than 1% of the aluminum metal material present in an aluminum sheet of conventional thickness for packaging, i.e. 6.3 μm. Metallic vapor deposition coatings require significantly less metallic material and typically provide a lower level of oxygen barrier properties.

[0079] Other examples of vapor deposition coatings are aluminum oxide (AlOx) and silicon oxide (SiOx) coatings. Generally, these coatings are more brittle and less suitable for incorporation into laminating packaging materials.

[0080] Other coatings for laminated packaging materials can be applied via a plasma-enhanced chemical vapor deposition (PECVD) method, in which a vapor of a compound is deposited onto the substrate under more or less oxidizing circumstances. Silicon oxide (SiOx) coatings by PECVD coating can, for example, achieve very good barrier properties under certain coating conditions and gas recipes.

[0081] The vapor deposition coating may alternatively be an amorphous hydrogenated carbon barrier layer applied by a plasma-enhanced chemical vapor deposition, PECVD, so-called diamond-like carbon (DLC) process. The DLC defines a class of amorphous carbon material that exhibits some of the typical properties of diamond. Preferably, a hydrocarbon gas, such as, for example, acetylene or methane, is used as the process gas in the plasma for producing the coating.

[0082] The innermost liquid-proof heat-sealed layer is therefore a layer of m-LLDPE, for good lamination properties and material strength, laminated even more contiguously to an intermediate layer of LDPE, also participating of heat sealing operations. The inner thermoplastic polymer layers of the inner layer portion can be applied by co-extrusion coating the molten polymers. They can also be co-extruded coated together with the molten adhesive polymer in the desired thicknesses of the respective layers.

[0083] Adhesive polymers suitable for laminating the heat sealable layers internal to a barrier sheet or film are so-called adhesive thermoplastic polymers such as modified polyolefins, which are mainly based on LDPE or LLDPE copolymers or functional group graft copolymers containing monomer units such as carboxylic acid functional groups, for example (meth)acrylic acid monomers or maleic anhydride (MAH) monomers (such as ethylene acrylic acid copolymer (EAA) or ethylene methacrylic acid copolymer (EMAA) ), ethylene-glycidyl(meth)acrylate copolymer (EG(M)A) or MAH-grafted polyethylene (MAH-g-PE). Another example of such modified polymers or adhesive polymers are the so-called ionomers or ionomer polymers. Preferably, the adhesive polymer is an ethylene acrylic acid copolymer (EAA) or an ethylene methacrylic acid copolymer (EMAA).

[0084] The barrier metal sheet or a barrier-coated film or sheet is laminated to the bulk layer by melt coextrusion therebetween and pressure into a gap between rotating rollers, a three-layer cast film being a core layer of mLLDPE supported on each side by a layer of LDPE, the LDPE layers bond to the paperboard and barrier layer, respectively.

[0085] To optimize the performance of melt extrusion coating and lamination, the mLLDPE polymer may have a melt index of 10 to 25, such as preferably 15 to 25 g/10 min at 190°C, 2.16 kg (ISO1133), while LDPE polymer can have a melt index of 4 to 12 g/10 min at 190°C, 2.16 kg (ISO1133).

[0086] In coextrusion coating or coextrusion lamination of pure mLLDPE, a relatively high melt index is required to avoid creating too much frictional heat, because pure mLLDPE gains very high viscosity at high extrusion speed.

[0087] The mLLDPE polymer may have a density of 907 to 918, such as 907 to 915 kg/m3. The LDPE polymer can have a density of 916 to 920 kg/m3. The density of polymers can be measured by ISO1872/1183.

[0088] The mLLDPE can have an Eta 0 value, from 400 to 2500 Pas, such as from 400 to 1200 Pas, while the LDPE can have an Eta 0 value from 2000 to 15000 Pas. The Eta 0 value is measured in accordance with TAPPI T702 and is a measure of the zero shear viscosity, which represents the melt viscosity property of an extruded cast thin film and its “drawdown” ability, i.e. the ability of the molten material to be pulled into thin films without breaking. Thus, drawdown is favored by a melt that is more viscous than elastic.

[0089] The mLLDPE can have a G' value of 5 to 20 Pa, while the LDPE can have a G' value of 100 to 150 Pa. The G' value is measured according to TAPPI T702 and is a measure of the storage modulus, which represents the melt elasticity of a thin cast extruded film, in turn representing the tendency towards so-called “throttling”, i.e. reduction of the width of the cast film. Thus, if the bottleneck is high, the fusion elasticity is low.

[0090] Both zero shear viscosity and storage modulus are rheological measurements made by an oscillatory method, thus exploring the viscoelastic behavior of a molten polymer, as described in more detail in TAPPI T702.

[0091] In a further embodiment, mLLDPE can have at least one melting point, from 95 to 105, such as 96 to 100°C, while LDPE can have a melting point from 105 to 115°C, such as from 105 to 110°C.

[0092] If you select a mLLDPE with a very low melting point to start melting for the sealing operation, the surface of the polymer will have greater friction and/or stickiness (adherence) when being handled in the filling machine and in coils and web handling. On the other hand, if the melting point to initiate melting for the sealing operation is too high, above 105°C, the sealing properties will not be as good and the sealing process will not be as robust.

[0093] Melting points can be measured in accordance with ASTM D3418 of the DSC, first scraping or removing the polymer from the individual layers by a microtome, such as a standard Leica microtome, and then analyzing the samples taken by the standard DSC, considering melting points on second heating at 0.5 to 10°C/min. The innermost layer portion of the mLLDPE innermost layer and the LDPE interlayer can first be separated from the adhesive polymer layer containing the carboxyl group by adding isopropanol at the interface and carefully pulling the innermost layer portion of the laminate. Having thus separated the portion of the innermost layer, to have free surfaces of each of the inner polymer layers, samples can be scraped from each surface by the microtome and subsequently analysed.

[0094] That the layers comprise or consist of mLLDPE and LDPE, respectively, can at least be confirmed with standard NMR (Nuclear Magnetic Resonance) analysis. By NMR analysis, the chain branching of the polymers can be studied, thus detecting the longer chain branches of LDPE and the shorter chain branches of mLLDPE. The adhesive polymer layer comprising the carboxylic functionality can be determined by FTIR analysis, also a tool well known to those skilled in the art of polymer analysis.

[0095] A good and quick understanding of which polymers are present in the innermost and innermost layers can, however, be obtained by mere standard DSC analysis of the innermost and innermost layers collected in a sample and studying the melting peaks in the second heating stage at 0.5 to 10°C/min. As the measured samples are small (only about 2 milligrams), a standard or slower cooling/heating rate of the DSC scan is required to separate the different peaks well enough from each other. A typical curve from such an analysis shows two melting peaks, or at least "clips" in the curve, one for mLLDPE at 95 to 105°C and another for LDPE at 105 to 115°C. As the melting points are relatively close together, the mLLDPE peak typically shows more as a “bounce” or a slight bend in the curve. When comparing with a corresponding curve for pure LDPE, the difference is very clear. From this curve, the expert understands that there are two polymers and, from the context, it is more likely that they are of the LDPE type and the other of the m-LLDPE type. Additional microtome sampling and DSC analysis can be done to confirm and compare with calibration curves for known pure polymers. This is explained in more detail in Figure 9 below. For the specific mLLDPE analyzed in a mixture with LDPE, each corresponding mLLDPE melting peak is shown as a bump or slope added on either side of the melting peak curve for the LDPE.

[0096] A similar approach can be adopted to analyze the components of the individual layers of the laminate portion.

[0097] When collecting samples of a polymer coated by extrusion or mixing, in a packaging material, or a package, it may be that the melting points and the melting curve are shifted from 0.5°C to a maximum of 2° C values higher than compared to granule or globule polymers.

[0098] The fact that the LLDPE polymer is a metallocene-catalyzed LLDPE, that is, an m-LLDPE, can be confirmed by spectrography using polarized X-ray radiation, such as the use of an Ametek Spectro XEPOS® EDPXRF equipment, to detect the presence of metallocene catalyst residues.

[0099] Finally, the thicknesses of the individual layers can be measured by well-established microtome and optical microscopy methods known to those skilled in the art.

[00100] In one embodiment, the mLLDPE polymer is a copolymer of ethylene with an alpha-olefin chosen from butene, hexene or octene.

[00101] The same mLLDPE can be used in the innermost layer as in the central layer of the laminate layer portion. With this choice, greater production efficiency and raw material logistics control will be possible. Furthermore, the balance of properties between the inner layer portion and the laminate layer portion becomes easier when one and the same mLLDPE polymer is used in both portions of the laminate.

[00102] For even greater efficiency and predictability of laminate properties, the LDPE polymer of the inner part is the same as that used in the support layers of the laminate layer portion.

[00103] In addition, the thermoplastic polymer used in the outer layer can be the same LDPE as that of the inner layer, so that the efficiency of production and planning is as high as possible, the only variations between the specifications of different packages being that the packaging laminate has different layer thicknesses, the different polymer grades being reduced to a minimum number and the order of the layers being the same.

[00104] According to one embodiment, according to today's state-of-the-art packaging materials for liquid boxes, the barrier layer portion is an aluminum foil. Aluminum foil normally has a thickness of 5 to 10 μm, such as 5 to 9 μm. A thick sheet of aluminum metal can provide almost absolute barrier properties for migrating substances such as gases such as oxygen gas and water vapor, aromas, odors, and also provides light barrier properties. Good barrier properties are necessary for the long-term preservation of food products. Depending on the type of food product, some barrier properties are more important than others. Milk and dairy products are, for example, particularly sensitive to the penetration of light into packaging and therefore require aluminum foil or similar light-blocking materials to allow for a long shelf life.

[00105] In particular, when the barrier layer is an aluminum foil, an adhesive polymer is needed to adhere well the layers of the inner layer portion to the interior of the barrier layer. This adhesive polymer must be based on a polyolefin polymer, i.e., being constructed from most polyolefin monomer units, such as ethylene, with a melt index of 4 to 12 g/10 min at 190°C, 2 .16 kg (ISO1133) and has a content of carboxylic functional groups from 3 to 10% by weight, for melt processing properties as well as optimal adhesion properties. Preferably, the adhesive polymer, as described above, is an ethylene acrylic (or methacrylic acid) copolymer or graft copolymer, such as EAA or EMAA.

[00106] In general, it was concluded that the thickness ratio of the total thickness of the inner polymer layers, that is, the sum of the thicknesses of the portion of the inner layer and the polymer adhesive layer, with the thickness of the portion of the polymer layer Laminate must be greater than 1 for most packaging specifications.

[00107] In a preferred embodiment, for portion packs and family size packs of volumes of up to 1 liter, with small openings, such as perforation openings or straw holes or the like, the central layer of the portion of the laminate layer has a thickness 4 to 8 μm and constitutes not more than 40% of the thickness of the total portion of the laminate layer, which has a total thickness of 25 μm or less, and the thickness of the innermost layer is 6 to 15 μm and constitutes not more than 50% of the total thickness of the inner polymer layers, which is 40 µm or less.

[00108] Preferably, for portion packs and family size packs of volumes of up to 1 liter, with small openings, such as perforation openings, straw holes or similar, the ratio between the total thickness of the inner layers of polymer and the thickness of the laminate layer portion is greater than 1.2, such as greater than 1.5, and for portion packs, is preferably greater than 1.6, such as greater than 2.0.

[00109] It was observed in experiments, and even in large data simulation series, that the thinner the portion of the laminate layer with a central layer of mLLDPE, the better tightness and barrier of the aluminum foil were obtained around the creases of the packages, and it can be understood that the risk of warping cracks that can appear in the barrier sheet in these places has been diminished. Further investigation showed that, above all, the size of the cracks was reduced, not the number of cracks.

[00110] Another observed effect was that when the thin portion of the laminate layer was kept constant and the thickness of the inner layer portion was increased, the barrier properties around the fold creases improved further. Thus, it was possible to decrease the thickness of the laminate layer more than expected and instead further increase the portion of the inner layer, further improving the strength and robustness of the heat seal, despite having removed some of the mLLDPE polymer. At the same time, the openability properties can be smoothly balanced, that is, improved.

[00111] Thus, at least for the smaller package sizes and the types of packages for perforating and opening the straw, it was observed that a ratio between the total thickness of the inner layers of the polymer and the thickness of the portion of the laminate layer of at least 1.3 and in many cases above 1.5 or even above 2.0, resulted in very good package integrity and oxygen gas barrier properties as well as openability properties of packages made from the material.

[00112] This supports a theory that by including a thin layer of mLLDPE in the laminate layer portion, there will be less plastic strain exerted on the aluminum foil during bending of the laminate material.

[00113] The volumetric layer can be a cardboard with a surface weight of 50 to 450 g/m2, such as 100 to 400 g/m2, such as 100 to 350 g/m2, such as 100 to 250 g/m2.

[00114] Normally, cardboards are chosen to have a bending stiffness of 0 to 475 mN, such as 80 to 260 mN. The thickness of a single cardboard can vary correspondingly from 50 to 600 µm.

[00115] According to the second aspect of the invention, the method for manufacturing the packaging laminate for liquid boxes comprises a step of laminating by extrusion a continuous sheet of the volumetric layer to a continuous sheet of the barrier layer portion by means of of melt coextrusion of the core layer of mLLDPE together with at least one backing layer of LDPE, between the webs, and pressure while solidifying the molten polymer in a space between the rollers, and an additional step of melt coextrusion which coats the innermost layer of the mLLDPE together with at least the intermediate layer of LDPE on a surface of the web comprising the barrier layer portion. The two main lamination steps can be performed in any order, depending on the configuration of the lamination production line.

[00116] It is advantageous that all the polymer layers of the laminate layer portion are coextruded together in a melt extrusion operation. By this co-extrusion configuration, the two LDPE support layers on each side of the thin center layer of mLLDPE can support the mLLDPE with its mass and heat contained in its polymeric mass, so that the mLLDPE flows more easily in the cast film curtain and adapt to the circumstances around the heating in the feed block and extruder die, as well as the cooling in the roll space of the press roll.

[00117] Similarly and for the same reasons, it is advantageous to allow all of the inner polymer layers within the barrier layer portion to be coextruded together in a melt extrusion operation. This is the most economical and rational way of applying the internal polymer layers, also because it allows a high lamination speed at typically above 300 m/min, such as above 400 m/min, even above 500 m/min, even above 500m/min, such as 600m/min and above.

[00118] According to the third aspect of the invention, there is provided a liquid, semi-liquid or viscous food packaging container, comprising the laminated packaging material of the invention. The packaging container can be made entirely from the laminated packaging material, fold forming a blank in sheet or continuous sheet form into a cuboid, another fold forming package or just a pouch type package. Alternatively, it can be used as a packaging material sleeve, to be combined with plastic bottle caps or the like.

[00119] The packaging containers of the invention have an improved performance, or at least maintained, in relation to the integrity of the package and the barrier properties, and are economical in several aspects, such as being poor in the raw materials used, and the efficiency of lamination and packaging laminate manufacturing, as well as the efficiency of packaging container production, being improved. By being able to optimize the polymeric layer thicknesses, the lamination process and the consumption of polymeric raw materials, it is consequently possible to reduce the overall carbon footprint of the laminated packaging material product, as well as the resulting packages made from it. .

[00120] The thermoplastic polymer of the innermost heat sealable layer consists substantially of a metallocene-catalyzed linear low density polyethylene (m-LLDPE). It may comprise a smaller amount of low density polyethylene (LDPE), such as up to 15, such as 10% by weight, maintaining the advantages of the invention.

Examples and description of drawings

[00121] In the following, embodiments of the invention will be described with reference to the drawings, in which: Fig. 1 is showing a schematic cross-sectional view of a laminated packaging material according to the invention, Fig. 2a schematically shows a preferred example of a method for laminating an aluminum foil barrier to a volumetric layer according to the invention, Fig. 2b schematically shows a preferred example of a method for laminating inner layers, including the inner layer portion of heat-sealable, liquid-tight thermoplastic polymers to the barrier layer portion, in accordance with the invention, Figs. 3a, 3b, 3c, 3d show typical examples of packaging containers produced from the laminated packaging material according to the invention, Fig. 4 shows the principle of how packaging containers can be manufactured from packaging laminate in a continuous roll-fed form, fill and seal process, Fig. 5 is a diagram showing how the openability can vary between three different material structures, one of which is in accordance with the invention, Fig. 6a is a diagram showing the general influence of a thinner portion of the laminate layer on the peak of plastic strain in aluminum foil and a comparison between a layer structure according to the invention and a layer structure according to a corresponding layer structure of the prior art, Fig. 6b is a diagram showing peak plastic strain in aluminum foil as a function of the total thickness of the laminate layer portion, Fig. 6c is a diagram showing plastic deformation in aluminum foil as a function of the total thickness of the inner polymer layers, Figs. 7a and 7b respectively show a diagram in which crack defects measured in the K-bend zone are plotted for a structure of material of the invention, in comparison with a structure of reference material, Fig. 8 shows the results of a heat seal platform test of different material structures at different power settings, and Fig. 9 shows an example of a possible melting diagram from the analysis of the two layers of the innermost layer portion together, with the DSC according to ASTMD3418.

[00122] In Fig. 1, there is thus shown, in cross-section, a first embodiment of a laminated packaging material 10 of the invention. It comprises a volumetric layer 11 of cardboard, with a grammage of approximately 200 g/m2 and a bending stiffness of 260 mN.

[00123] Inside the cardboard layer 11, the laminated material comprises a portion of the barrier layer 12, in this case an aluminum foil 6.3 μm thick.

[00124] The barrier layer 12 is laminated to the volumetric layer 11 by a portion of the laminate layer 13, consisting of a central layer of mLLDPE 14, with adjacent backing layers of LDPE, 15, 16, on both sides. Backing layer 15 connects core layer 14 to bulk layer 11, while backing layer 16 connects core layer 14 to portion of barrier layer 12.

[00125] An inner layer portion 17 of liquid-tight heat sealable thermoplastic polymer layers is applied to the inside of the barrier layer 12. The inner layer portion consists of an innermost layer of mLLDPE 18 and an intermediate layer of LDPE 19.

[00126] In case the barrier layer portion 12 is an aluminum foil, the inner layer portion 17 is bonded to the aluminum foil 12 with an interjacent layer of an adhesive polymer 20.

[00127] The outer side of the volumetric cardboard layer 11 is covered with an outer layer 21 comprising LDPE, for heat sealing and tightness from the outside of a package made from the packaging laminate.

[00128] In this example, the same mLLDPE polymer is used in the innermost layer 18 as in the center layer 14 of the laminate layer portion 13. The mLLDPE used in this specific example is from Dow, namely Elite® 5860.

[00129] Furthermore, the same LDPE polymer is used in the intermediate layer 19 of the inner layer portion 17 as in the backing layers 15, 16 of the laminate layer portion 13. The LDPE used was 19N730 from Ineos.

[00130] Furthermore, the same LDPE was used in the outermost outer layer 21.

[00131] In Fig. 2a, is illustrated schematically as a continuous sheet of volumetric cardboard layer 11, as depicted in Fig. 1, is routed from a reel 21 and extrusion laminated to a continuous sheet of aluminum foil barrier layer 12, which is routed from a reel 22. A molten polymer curtain 23 of the laminate layer portion 13, from the core layer 14 and the backing layer 15 and 16 on each side thereof, is extruded 24 into a lamination space 25, between the bulk layer 11 and the barrier layer 12, to be pressed together and cooled to solidifying the molten polymer, thereby permanently adhering the bulk and barrier layer portion together to produce a pre-laminate 26. The resulting pre-laminate is forwarded to the next run of the laminating process, in this case as described in more detail in connection with Figure 2b.

[00132] In Fig. 2b, it is schematically illustrated how the pre-laminate web 26 of the bulk and barrier layers produced in Figure 2a is routed to a lamination roller gap 27. In the roller gap 27, a fused curtain 28 of the three inner layers of polymer, i.e., the adhesive polymer layer 20 and the inner layer portion 17 of the innermost layer 18 and intermediate layer 19 are co-extruded 29 downwards into the gap between laminating rollers 27 and cooled to be coated as a film coating on the opposite side of the barrier layer portion 12, i.e., inside the aluminum foil, pressing and solidifying the polymer layers 18, 19, 20 on the surface of the continuous sheet of aluminum foil. The resulting laminate 30 can be routed for further lamination of the outer LDPE layer on the outside of the bulk layer, or if this has already been done, to a winding station for further transport and storage of the packaging laminate on a reel.

[00133] Fig. 3a shows an embodiment of a packaging container 30a produced from the packaging laminate 10 according to the invention. The packaging container is particularly suitable for drinks, sauces, soups or the like. Typically, such a package has a volume of about 100 to 1000 ml. It can be of any configuration, but is preferably brick-shaped, with longitudinal and transverse seals 31a and 32a, respectively, and optionally an opening device 33. In another embodiment, not shown, the packaging container can be shaped like a wedge. To achieve a “wedge shape”, only the bottom of the carton is formed by folding, so that the transverse heat seal of the bottom is hidden under the triangular corner flaps, which are folded and sealed against the bottom of the carton. The top section cross seal is left unfolded. In this way, the semi-folded packaging container is still easy to handle and dimensionally stable when placed on a shelf in the food store or on a table or the like.

[00134] Fig. 3b shows a preferred alternative example of a packaging container 30b produced from an alternative packaging laminate in accordance with the invention. The alternative packaging laminate is thinner because it has a thinner volumetric cellulose layer 11 and therefore is not dimensionally stable enough to form a cuboidal, parallelepiped or wedge-shaped packaging container, and is not formed by folding after the transverse seal 32b. Thus, it will remain a pillow-shaped pouch-like container and will be distributed and sold in this form.

[00135] Fig. 3c shows a gable top package 30c which is formed by folding a pre-cut sheet or blank from the laminated cushioning material comprising a volumetric layer of paperboard and the durable barrier film of the invention. Also flat top packages can be formed from similar blanks of material.

[00136] Fig. 3d shows a bottle-like package 30d, which is a combination of a sleeve 34 formed from pre-cut blanks of the laminated packaging material of the invention, and a top part 35, which is formed from injection molding plastics in combination with an opening device such as a screw cap or similar. This type of packaging is, for example, marketed under the trade names Tetra Top® and Tetra Evero®. These particular packages are formed by affixing the molded top 35 with an opening device affixed in a closed position, to a tubular sleeve 34 of laminated packaging material, sterilizing the bottle top cap thus formed, filling it with the food product and finally forming by folding the bottom of the package and sealing it.

[00137] Fig. 4 shows the principle described in the introduction to the present application, i.e. a continuous sheet of cushioning material is formed into a tube 41 by the longitudinal edges 42 of the web being joined together at an overlapping joint 43. The tube is filled 44 with the intended liquid food product and is divided into individual packages by repeating transverse seals 45 of the tube at a predetermined distance from each other below the level of the content filled in the tube. The packages 46 are separated by incisions in the transverse seals and given the desired geometric configuration by forming folds along crease lines prepared in the material.

[00138] The diagram in Fig. 5 shows the opening force required to open a perforation opening of a 1 liter family size package of the type Tetra Brik® Slim, made from a reference material structure and a material structure according to the invention, as well as a hybrid material structure.

[00139] The X axis represents the deformation measured in the material, while the Y axis measures the force required to open the same, along a standard perforation tear line.

[00140] The three comparable laminate structures are shown in Table 1.

[00141] The reference laminated packaging material has a state-of-the-art two-layer interior with a mixture of mLLDPE and LDPE and a laminate layer of LDPE.

[00142] The laminated packaging material, No. 5210, has the same inner layer configuration as the reference, but a laminated layer portion as according to the invention.

a) b) c)[00143] The comparable laminated packaging material, No. 5211, is in accordance with the invention. Table 1: Ref TBA/ml 1000S

a) b) c)

[00144] In all three comparable laminate structures, the volumetric paperboard layer 51 is the same, the aluminum foil barrier layer 52 is the same, and the outermost heat sealable layer of LDPE 53 is the same and has the same thickness, i.e. 13.0 μm (12 g/m2). In addition, all three structures have a bonding layer of EAA 54 that bonds the inner heat sealable layer(s) to the inside of aluminum foil, with a thickness of 6.4 μm (6 g/m2).

[00145] The reference sample material structure a) has the structure shown in Table 1, that is, it has a single laminate layer of 21.7 μm (20 g/m2) of LDPE 55 and an innermost layer 56 of a mixture of 70% by weight of mLLDPE (Dow Elite 5860) and 30% by weight of LDPE (770G), with a thickness of 20.9 µm (19 g/m2).

[00146] A different comparison material structure b) numbered 5210, has the same inner layer structure as the reference sample, but has a different laminate layer portion, which is the laminate layer according to the invention, with a center layer of 4.4 µm (4 g/m2) mLLDPE and a backing layer of 5.4 µm (5 g/m2) LDPE on each side.

[00147] The laminate material structure according to the invention is numbered 5211 and has a laminate layer portion similar to structure b), but in which the central and supporting layers have a thickness of 6.5 μm. The inner layer portion has two heat sealable layers, i.e. an innermost layer of 6.6 µm (6 g/m2) mLLDPE and an intermediate layer of LDPE, between the adhesive polymer layer and the innermost layer , at 13.0 µm (12 g/m2). Thus, the innermost layer does not, in this case, contain LDPE, and is a considerably thinner layer, but instead has an adjacent, intermediate, thicker layer of LDPE.

[00148] The diagram in Fig. 5 thus shows that the reference sample material requires a higher initial force for opening a drill hole and with a continuous opening resistance clearly at a higher level than the other two samples. It is also possible to observe that the curves, representing the opening resistance from the beginning of the opening until the perforation is completely torn, are similar, but at different levels of the required and applied force.

[00149] Furthermore, the structure of the material according to the invention, 5211, has the lowest required opening force for all three samples.

[00150] Sample 5210, which has the same inner layer configuration as the reference sample, but a different portion of the laminate layer, requires a lower opening force than the reference sample, probably due to the fact that the laminate layer be considerably thinner at only 15.2μm (14g/m2) in total, but it has a mLLDPE as the core layer, but with a low thickness of only 4.4μm (4g/m2).

[00151] The structure of the material according to the invention further reduced the required opening force, instead of a mixture of mLLDPE and LDPE in the inner layer, with a thinner layer of mLLDPE only. This was a surprising and illuminating effect, considering that it was previously thought necessary to blend an mLLDPE so as not to make it too strong to open and too difficult to process, for liquid case packaging laminates.

[00152] In addition to the measured opening force, an independent panel of test openers found the sample packs made from the 5211 structure more “robust” to open, that is, meaning that there was less plastic waste created around the edge of the laminate of opening, as a result of opening a package.

[00153] A similar test and similar results were made in relation to these three material structures, based on packages with a straw hole, to be penetrated by a straw, in order to be opened and accessed for drinking. The straw hole, to be opened, then comprised all layers of the laminate, except the volumetric layer, as described above.

[00154] In a series of tests of different layer thickness configurations of laminated material structures of the invention, the peak of plastic deformation in aluminum foil during bending was estimated by simulation and visualized in diagrams 6a, 6b and 6c, in function of the polymer layer thicknesses. The material layer structures were as described in Tables 2 and 3, where the LDPE used in the interlayer of the innermost layer portion and in the laminate layer portion was Novex® 19N730 from Ineos. The mLLDPE used was Elite® 5860 from Dow. When the mLLDPE was mixed into the innermost layer portion, it was mixed with Dow LDPE 770G. Also in the outer layer, the LDPE used was Novex® 19N730 from Ineos.

[00155] The adhesive polymer used in all examples was Primacor® 3540 from Dow.

[00156] Plastic deformation is the deformation obtained in the plastic region above the yield point in which the metal does not return to its original shape after removal of deformation. Higher plastic strains mean a higher risk of sheet cracking. An estimate of the peak plastic strain is therefore a measure of the risk of strain that is affecting the initiation of cracks in the aluminum barrier sheet in the formation of package folds. It has been observed that leaf crack initiations are connected to increased oxygen transmission (OTR) through the aluminum foil barrier and laminated cushioning material. A lower peak of plastic deformation in the barrier material can thus result in improved oxygen barrier properties of the laminated packaging material comprising the layer of barrier material when formed by plying packages.

[00157] The diagram in Fig. 6a shows the peak of plastic deformation obtained in the aluminum foil, from test runs 2, 4, 3 and 5. The simulations were made based on the scenario of bending the laminated packing materials, producing the highest single bend deformation of the foil aluminum foil, i.e. folding the laminate so that the outer part of the material is folded against itself (the aluminum foil being located inside the thick volumetric layer). Warp was tested at a bend angle of 100 degrees.

[00158] It can be seen that, with a higher thickness of the laminate layer portion, comparing rounds 2 and 3 and 4 and 5, respectively, there is a greater peak of plastic deformation in the aluminum sheet and, therefore, , probably also increased transfer or permeation of oxygen through the laminate.

[00159] Likewise, there is a greater peak of plastic deformation in the aluminum foil layer structure of the prior art (round 2) than in a corresponding layer structure according to the invention (round 4), which has the same overall thickness of the polymer layers in the layer portion of the laminate and within the aluminum foil, respectively. This is also the conclusion of the comparison between round 3 and round 5.

[00160] The diagram in Fig. 6b shows the peak of plastic deformation in aluminum foil as a function of the total thickness of the laminate layer portion structured according to the invention (runs 8 to 13). It can be concluded from the diagram that by decreasing the total thickness of the laminate layer portion from 20 to 9 μm, the peak plastic strain of the aluminum foil also decreased from 22 to 15% (expressed as the ratio of the length of the sample after deformation divided by the length of the sample at the beginning). The cross represents a reference sample (round 7) with a single innermost layer of a mixture of mLLDPE and LDPE, the total inner layers 27.4 µm (25 g/m2) thick, and a layer portion of laminate relatively thick layer of LDPE of about 21.8 µm (20 g/m2).

[00161] The diagram in Fig. 6c shows plastic deformation in aluminum foil as a function of the total thickness of the inner polymer layers. It can be concluded from this diagram that by increasing the total thickness of the inner polymer layers, plastic deformation in the aluminum foil decreased even more. The left square dot represents a reference sample not in accordance with the invention, which has a laminate thickness of 22 µm, i.e. 20 g/m2. By increasing the thickness of the inner layer of the reference sample, the upper right square point was obtained, that is, the plastic deformation increased. However, when a laminate layer configuration according to the invention was used, the lower right point was obtained, i.e. the plastic deformation remained unchanged. In other samples of the invention, with thinner portions of the laminate layer, the plastic deformation decreased with the increase in the thickness of the inner layer.

[00162] The samples of the laminate layer portion of 20 g/m2 are taken from rounds 2, 4 and 7 of the Table. The 15 samples are collected from rounds 9 and 10, while the 12 samples are collected from rounds 11 and 12 in the table.

[00163] The simulation test rounds that result in the diagrams in Figures 6b and 6c are described further in Tables 2 and 3.

[00164] Thus, it is concluded from round 2-13 that the thicker polymer layers in the laminate layer portion in general give a higher plastic strain peak in the aluminum sheet. It is indicated in rounds 4-6 that a combination of a thinner laminate layer portion and a thicker total inside layer (i.e., thicker innermost layer portion) can give the least amount of warping in aluminum foil. It is also observed in runs 2-5 that the structure of the laminate layer portion according to the invention, i.e. including a core layer of mLLDPE at a certain proportional thickness, can cause less warping than runs with LDPE.

[00165] Again, from test runs 7-13, it can be concluded that a thinner portion of the laminate layer and a thicker total inner layer according to the invention (thicker portion of the innermost layer) can provide less deformation in the aluminum foil and consequently better gas barrier properties should be obtained.

[00166] The diagram in Fig. 7a shows the width of actual detected cracks measured in the bend zone K of an aluminum foil barrier in a laminated material structure of the invention and in the reference sample material structures, when formed into bends in cuboidal packing containers. A packing material is exposed to high strain in the K-bend zone of bending in a packing container of cuboidal shape, such as a brick-shaped parallelepiped shape. The width of the cracks formed was measured and the values were plotted for the three sample laminate layer structures, which are the same except for the characteristics described below.

[00167] The general structure is /(12 g/m2) 13.0 μm LDPE/ 260 mN cardboard/ (12 g/m2) laminate layers of about 13 μm/ Al foil 6 μm/ total of 25 g/ m2 of inner layers/

Reference sample No. 7465:

[00168] A laminated layer of LDPE at (12 g/m2) 13.0 μm and a portion of the innermost layer of a heat sealable layer at (19 g/m2) 20.9 μm and an adhesive layer of (6 g/m2) at 6.4 µm, the mixture being 70% by weight mLLDPE and 30% by weight LDPE.

Reference sample 7466:

[00169] A laminated layer of LDPE at (12 g/m2) 13.0 μm and a total internal sealing layer at (25 g/m2) 27.2 μm, however comprising an innermost layer of pure mLLDPE. The inner layer structure is (6 g/m2) 6.4 µm adhesive polymer, (10 gm2) 10.9 µm LDPE middle layer, and (9 g/m2) 9.9 µm mLLDPE.

Sample according to invention 7467:

[00170] A portion of the laminate layer according to the invention, with a central layer of mLLDPE with (4 g/m2) thickness of 4.4 μm and binding and support layers of LDPE with (4 g/m2) thickness of 4.4 µm each, on each side of the center layer, the total portion of the laminate layer being (12 g/m2) 13.2 µm thick, and a total inner sealing layer of (25 g/m2) 27.2 µm, comprising an innermost layer of pure mLLDPE. The structure of the inner layer is (6 g/m2) 6.4 µm adhesive polymer, (10 g/m2) 10.9 µm LDPE, and (9 g/m2) 9.9 µm mLLDPE.

[00171] The greater the initial width of a crack appearing in the K-fold zone of the barrier layer, the greater the risk of later formation of larger cracks in the barrier material, due to the handling and distribution of the packages, so that breaks and defects in adjacent layers can form, potentially even worse, causing the packaged product contents to leak or bacteria to enter the filled product from the inside of the package. A crack in the K-fold zone of the barrier material can lead to loss of shelf life due to the increased amount of oxygen migrating into the filled packaging vessel. Thus, it is important to keep the width of initial K-fold zone cracks formed by folding in cuboidal packages as low as possible in order to avoid or reduce the risk of package integrity or performance issues after stressful handling and distribution.

[00172] It is clearly shown that a significant decrease in the width of cracks formed in the barrier layer of aluminum foil, in the K-bend zone, is obtained by sample 7467, i.e. the laminate layer structure of the invention. This laminate structure should therefore also provide improved packaging performance from a K-fold zone point of view.

[00173] Fig. 7b shows the same relationship and conclusion regarding larger packaging containers with a corresponding laminated material structure, but thicker and stronger to be suitable for larger quantities of liquid food products such as 1.5 to 2 liters.

[00174] The samples of laminated packaging material were those described below and were formed by folding into cuboidal packages with the same parallel epipedic shape (“thin”), of 1.5 liters. The general structure is /(16 g/m2) LDPE 17.4 μm outside/ cardboard 370 mN/ (20 g/m2) LDPE (or /7/6/7/ g/m2) / Al foil 6 μm / (14 g/m2) 15.2 µm LDPE/ (15 g/m2) mixture of mLDPE+ LDPE (70+30% by weight)/ (or /6/23/6/ g/m2). Reference sample No. 6908:

[00175] A laminate layer of LDPE at (30 g/m2) 32.6 μm and a portion of the innermost layer of a heat sealable layer at (19 g/m2) at 20.9 μm, an adhesive layer of (6 g/m2) 6.4 μm, and a middle layer of LDPE at (20 g/m2) 21.7 μm, i.e. a total inner layer thickness of 49.0 μm, the innermost layer mixture being a mixture of 70% by weight of mLLDPE and 30% by weight of LDPE. Reference sample 6909:

[00176] A laminate layer of LDPE at (20 g/m2) 21.7 μm and a portion of the innermost layer of a heat sealable layer at (15 g/m2) at 16.5 μm, an adhesive layer of (6 g/m2) 6.4 μm, and an LDPE interlayer at (14 g/m2) 15.2 μm, i.e. a total inner layer thickness of (35 g/m2) 38.1 μm, the blend being 70% by weight mLLDPE and 30% by weight LDPE. Sample according to invention 6913:

[00177] A portion of the laminate layer according to the invention, with a central layer of mLLDPE with (6 g/m2) 6.6 μm thick and connecting layers and support of LDPE with (7 g/m2) 7 .6 μm thick each, on each side of the center layer, the total portion of the laminate layer being (20 g/m2) 21.8 μm thick and a total internal sealing layer at (39 g/m 2 ) μm , with an innermost layer of pure mLLDPE. The structure of the inner layer is (6 g/m2) 6.4 µm adhesive polymer layer, (27 g/m2) 29.3 µm LDPE middle layer, and (7 g/m2) mLLDPE of the innermost layer of 7.7 µm.

[00178] Again, there was a significant decrease in the width of cracks formed in the barrier layer of aluminum foil, in the K-bend zone, obtained by sample 6913, that is, the structure of the laminate layer of the invention. This laminate structure, therefore, may have improved oxygen barrier properties and package integrity from a K-fold zone point of view.

[00179] The structures of the invention, as shown in examples 7467 in Fig. 7a and 6913 in Fig. 7b, also have improved resistance to puncture or breakage in the laminate layer portion caused by fibers and uneven surfaces of the bulk and barrier layers.

[00180] Fig. 8 shows the results of a heat seal platform test at different power settings of different material structures. Thus, it can also be concluded that the heat seal window is enlarged by the structure of the laminate material of the present invention, compared to a reference structure which has a mixed innermost layer of mLLDPE and LDPE. A wider heat seal window is beneficial because the sealing operation can be started at a lower temperature and allows more time for the polymer chains of the sealing polymer to untangle and re-tangle across the interface of the two polymer surfaces to be be prohibited from each other. Legend: X: locked seal O: tight seal Sample 6322: mLLDPE with melting point 97°C and density 907 kg/m3 as innermost sealing layer; Dow Elite 5860 Material structure from outside to inside (g/m2): //16 LDPE/ppr 260 mN/ 9 LDPE/ 10 mLLDPE/ 9 LDPE/ sheet Al 6.3/ 6 EAA/ 18 LDPE/ 10 mLLDPE/ / 6424: mLLDPE/LDPE blend as the innermost sealing layer; mLLDPE: Elite 5860 from Dow and LDPE: 770G from Ineos Material structure from outside to inside (g/m2): //16 LDPE/ppr 260 mN/ 30 LDPE/ sheet Al 6.3/ 6 EAA/ 17 LDPE/ 12 mLLDPE// 6425: mLLDPE with a melting point of 106 °C and a density of 918 kg/m3 as a sealing layer; Exxon Mobil Exceed 0019XC Material structure from outside to inside (g/m2): //16 LDPE/ppr 260 mN/ 9 LDPE/ 10 mLLDPE/ 9 LDPE/ sheet Al 6.3/ 6 EAA/ 18 LDPE/ 10 mLLDPE //.

[00181] Fig. 9 thus shows an example of a possible melting diagram of the analysis of the two layers of the innermost portion (an LDPE layer and an mLLDPE layer), with DSC according to ASTMD3418 in the second heating at 10°C/min. The mLLDPE melting point peaks “shine” across the LDPE melting curve 93 since they are very close together and the melting energy areas overlap. Thus, there is a melting point of the mLLDPE layer, visible as a “bump” on the slope of the LDPE curve at 92 in Fig. 9, and there is another melting point of mLLDPE on the weakened slope 91 of the LDPE curve at the end of the melting process. A ramp rate of 10°C/min, sometimes a lower ramp rate, is required in order to “separate” the melting point peaks, to be visible on the DSC curve in this way.

[00182] In conclusion, the above embodiments and evaluations show that the invention, as defined by the claims, makes possible the production of packaging for liquid boxes with improved openability properties and improved packaging integrity properties, as well as properties of Improved gas barrier. The packaging material of the invention is suitable for high-speed laminating processes, as well as exhibiting increased robustness in high-speed filling and sealing processes. The invention also makes it possible to reduce the total amounts of polymeric raw materials involved and thus provide a resource efficient packaging material.

[00183] The invention is not limited by the embodiments shown and described above, but may vary within the scope of the claims. As a general remark, the proportions between layer thicknesses, distances between layers and the size of other features and their relative size in comparison with each other, should not be taken as shown in the figures, which merely illustrate the order and type of layers in relation to each other and all other characteristics to be understood as described in the text of the specification.

Claims (16)

1. Packing laminate for liquid cases, characterized in that it has the following laminated layer portions, a. an outermost liquid-tight and heat-sealable layer of a thermoplastic polymer (21), outermost meaning directed towards the outside of a packaging container made from the packaging laminate, b. a volumetric layer (11) of carton or cardboard, the outermost liquid-tight, heat-sealable layer being applied to the outside of the volumetric layer, c. a barrier layer portion (12), d. a portion of the lamination layer (13), which connects the opposite inner side of the bulk layer to the portion of the barrier layer, e.g. an innermost layer portion (17) of liquid-tight, heat-sealable polymer applied to the opposite inner side of the barrier layer portion f. optionally, a layer of an adhesive polymer (20), which bonds the innermost layer portion to the barrier layer portion and has a thickness of 4 to 9 µm, the innermost layer portion with an intermediate layer (19) of low density polyethylene (LDPE) and an innermost layer (18), which forms the inner surface of a packaging container made from the packaging laminate, of a linear low density polyethylene produced with a metallocene or metallocene-type catalyst ( mLLDPE), the innermost layer portion, and the adhesive layer constituting the inner polymer layers (13a), wherein the lamination layer portion has a core layer (14) of an mLLDPE and a backing layer of LDPE on each side of the core layer, the LDPE backing layers connecting the core layer to the bulk layer and the portion of the barrier layer, on the respective sides of the core layer, and wherein the thickness of the core layer is from 4 to 15 µm and constitutes no more than 40% of the total thickness of the lamination layer portion, the total thickness of the lamination layer portion being less than 50 µm and wherein the thickness of the innermost layer of mLLDPE is 6 to 20 µm and constitutes not more than 50% of the total thickness of the portion of the inner polymer layers, the total thickness of the inner layers being up to 50 µm and wherein the mLLDPE of the innermost layer has at least a melting point of 95 to 105°C and wherein the LDPE of the intermediate layer has a melting point of 105 to 115°C. 2. Packaging laminate for liquid boxes according to claim 1, characterized in that the mLLDPE polymer has a melt index of 10 to 25, such as 15 to 25 g/10 min at 190°C, 2 .16 kg (ISO1133), while the LDPE polymer has a melt index of 4 to 12 g/10 min at 190°C, 2.16 kg (ISO1133). 3. Packaging laminate for liquid boxes according to any one of claims 1 and 2, characterized in that the mLLDPE of the innermost layer (18) is the same as that used in the central layer (14) of the laminate layer portion . 4. Packing laminate for liquid boxes according to any one of claims 1 to 3, characterized in that the LDPE polymer of the intermediate layer of the inner layer portion is the same as that used in the support layers of the laminate. 5. Packaging laminate for liquid boxes according to any one of the preceding claims, characterized in that the LDPE polymer of the intermediate layer of the inner layer portion is the same as that used in the outer layer. 6. Packaging laminate for liquid boxes according to any one of the preceding claims, characterized in that the barrier layer portion (12) is an aluminum foil. 7. Packaging laminate for liquid boxes according to any one of the preceding claims, characterized in that the adhesive polymer (20) has a melt index of 4 to 12 g/10 min at 190°C, 2.16 kg (ISO1133) and has a content of carboxylic functional groups from 3 to 10% by weight. 8. Packaging laminate for liquid boxes according to any one of the preceding claims, characterized in that the thickness ratio of the total thickness of the inner polymer layers (13a) to the thickness of the portion of the laminate layer (13) is greater than 1. 9. Packaging laminate for liquid boxes according to any one of the preceding claims, characterized in that the volumetric layer (11) is a cardboard with a surface weight of 50 to 450 g/m2. 10. Packaging laminate for liquid boxes according to any one of the preceding claims, characterized in that the central layer of the laminate layer portion has a thickness of 4 to 8 μm and constitutes no more than 40% of the thickness of the total portion of the laminate layer, which has a total thickness of 25 µm or less, and the thickness of the innermost layer is 6 to 15 µm and constitutes not more than 50% of the total thickness of the inner polymer layers, which is 40 µm or less. 11. Packaging laminate for liquid boxes according to claim 10, characterized in that the thickness ratio of the total thickness of the inner polymer layers to the thickness of the laminate layer portion is greater than 1.3, as greater than 1.5, as greater than 1.8, as greater than 2.0. 12. Packaging laminate for liquid boxes according to any one of claims 10 or 11, characterized in that the volumetric layer (11) is a cardboard with a surface weight of 100 to 400 g/m2, such as 100 to 350 g/m2, such as from 100 to 250 g/m2. 13. Method for manufacturing a packaging laminate for liquid boxes as defined in any one of claims 1 to 12, characterized in that it comprises a lamination step by extrusion from a continuous sheet of the volumetric layer to a continuous sheet of the portion of the barrier layer by means of melt co-extrusion of the core mLLDPE layer together with at least one backing layer of LDPE, between the webs, and pressure while solidifying the molten polymer in a gap between the rollers, and an additional step of melt coextrusion coating the innermost layer of the mLLDPE together with at least the intermediate layer of LDPE onto a surface of the web comprising the barrier layer portion. 14. Method for manufacturing a packaging laminate for cases of liquid according to claim 13, characterized in that all polymer layers of the laminate layer portion are co-extruded together in a melt extrusion operation. 15. Method for manufacturing a packaging laminate for liquid boxes according to any one of claims 13 or 14, characterized in that all the inner layers of polymer, that is, inside the portion of the barrier layer, are coextruded together in a melt extrusion operation. 16. Packaging container, characterized in that it is manufactured from the packaging laminate for liquid boxes as defined in any one of claims 1 to 12.

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