Method for producing a laminated packaging material, packaging material obtained by this method, and packaging containers produced from this packaging material

Abstract

To provide a method of manufacturing laminated cellulose-based liquid or semi-liquid food packaging materials, which reduces costs.SOLUTION: The invention relates to a method for manufacturing a laminated cellulose-based liquid or semi-liquid food packaging material, wherein the laminated packaging material has a spacer layer of low-density cellulose, an outside module comprising a substrate layer having a print surface, and an inside material module comprising a barrier layer or barrier coating. The invention further relates to a laminated packaging material obtained by the method, and to a packaging container for liquid food packaging, comprising the laminated packaging material or being made from the laminated packaging material obtained by the method.SELECTED DRAWING: Figure 1a

Description

[Technical Field]

[0001] The present invention relates to a laminated packaging material and a method for producing the laminated packaging material.

[0002] Furthermore, the present invention relates to packaging containers comprising or made from laminated packaging material, in particular packaging containers intended for packaging liquid food products comprising laminated packaging material. [Background technology]

[0003] Single-use, disposable packaging containers for liquid foods are often produced from paperboard or carton-based packaging laminates. One such commonly found packaging container is marketed under the trademark Tetra Brik Aseptic® and is adapted for the aseptic packaging of liquid foods, such as milk, fruit juice, and the like, sold for long-term ambient storage. The packaging material in this known packaging container is a laminate comprising a bulk layer, typically made of paper or paperboard, and an outer, liquid-tight thermoplastic layer. To render the packaging airtight, particularly oxygen-tight, for aseptic packaging and milk or fruit juice packaging purposes, for example, these packaging laminates typically comprise at least one additional layer, most commonly aluminum foil.

[0004] On the inside of the laminate, i.e. on the side of a container made from the laminate intended to face the filled food product, there is an innermost layer applied on top of the aluminum foil, which may consist of one or several partial layers comprising a heat-sealable thermoplastic polymer, such as an adhesive polymer and / or a polyolefin, etc. And, outside the bulk layer, there is an outermost heat-sealable polymer layer.

[0005] Packaging containers are typically produced by modern, high-speed packaging equipment of the form-fill-seal type from webs or preformed blanks of packaging material. Thus, packaging containers can be manufactured by transforming a web of laminated packaging material into a tube by welding together the innermost and outermost heat-sealable thermoplastic polymer layers, thereby uniting the longitudinal edges of the web to one another at overlapping joints. The tube is filled with the intended liquid food product and then divided into individual packages by repeatedly transversely sealing the tube at predetermined distances from one another below the level of the contents in the tube. The packages are separated from the tube by cutting along the transverse seals and given the desired geometric configuration, usually a parallelepiped or rectangular prism, by folding and forming the packaging material along prepared creases.

[0006] The main advantage of this packaging concept consisting of continuous tube forming, filling and sealing is that the web can be continuously sterilized just before tube forming, offering the possibility of an aseptic packaging method, i.e. a method in which the filled liquid contents and the packaging material itself are reduced in bacteria and the filled packages are produced under clean conditions so that they can be stored for long periods even at room temperature without the risk of microbial growth in the filled product. Another important advantage of Tetra Brik® type packaging methods is the possibility of continuous high-speed packaging, which, as mentioned above, has a considerable impact on cost-effectiveness.

[0007] Packaging containers for sensitive liquid foods, such as milk or juice, can also be produced from sheet blanks or pre-formed blanks made of the laminated packaging material of the present invention. Packages are produced from tubular blanks of the packaging laminate that are folded flat by first assembling the blanks to form an open, tubular container capsule, one open end of which is closed by folding and heat-sealing an integral end panel. The closed container capsule is then filled with the food product, such as juice, through the open end of the container capsule, after which it is closed by further folding and heat-sealing the corresponding integral end panel. One example of a packaging container produced from sheet and tubular blanks is the conventional so-called gable-top package. There are also packages of this type that have molded tops and / or screw caps made of plastic.

[0008] The aluminum foil layer in the packaging laminate provides gas barrier properties that are significantly superior to most polymeric gas barrier materials, and traditional aluminum foil-based packaging laminates for aseptic packaging of liquid foods remain the most cost-effective packaging materials available on the market today for their performance levels.

[0009] Any other material that competes with such foil-based materials must be cost-effective in terms of raw materials, have comparable food preservation properties, be sufficiently mechanically stable, and be as low in complexity to transform into a finished packaging laminate.

[0010] Further reductions in the cost of today's packaging materials can be achieved by reducing the thickness of the polymer layer or by replacing the aluminum foil barrier with one or more different barrier layers, but this has proven to be very difficult. Another way to save costs, which has not previously been considered practical in the field of liquid carton packaging, would be to reduce the cellulose-based bulk layer by using less cellulose fiber material, either in type and / or amount. This has previously been considered undesirable because it compromises important properties such as mechanical strength and package integrity, as well as the barrier properties of the material. While paperboard accounts for the majority of liquid carton packaging materials, it also represents a large portion of the overall cost of the packaging material.

[0011] A further requirement for future laminated packaging materials for liquid packaging containers is that the appearance of such packaging containers must be highly differentiated, i.e., by providing new, interesting and attractive decorations or tactile features to attract consumers and retailers. Such features are, for example, background effects to printed decorative patterns such as gold metallization or other different shiny colors, embossed and engraved features such as holographic decorations, tactile or relief surface effects, matte / glossy surfaces, etc. The increasing demand for such differentiation options is difficult because the addition of features and materials usually automatically involves higher costs for raw materials and / or manufacturing processes. Summary of the Invention [Problem to be solved by the invention]

[0012] In view of the above, it is an object of the present invention to provide a new method for reducing the cost of packaging materials for laminated cellulose-based liquid or semi-liquid foods.

[0013] It is also a general object of the present invention to provide a method for producing, at low cost, a cellulose-based packaging material having sufficient mechanical stability and good barrier and integrity properties to meet the needs of packaging materials laminated to liquid cartons.

[0014] Another object of the present invention is to provide such laminated packaging materials at low cost with an increased content of bio-based and renewable materials, i.e., materials from sources that do not utilize fossil raw materials.

[0015] A still further object is to provide a method for producing a cellulose-based laminated packaging material based on a reduced bulk or core layer that has insufficient mechanical performance for liquid packaging, such as weakened or reduced bending stiffness, compared to existing liquid packaging paperboard as currently designed and produced.

[0016] It is a particular object of the present invention to provide a cost-effective, non-foil, cellulose-based, heat-sealable packaging laminate with optimum compressive strength and bending stiffness for the purpose of producing aseptic packaging containers for long-term ambient storage of nutritionally maintained liquid foods.

[0017] A still further specific object is to provide such a packaging material that does not have the problem of curling due to moisture, i.e., has edge portions of the web of laminated packaging material that remain flat and are at the same level as the remainder of the web or blank of packaging material.

[0018] Another specific object is to provide such a packaging laminate that has decorative and tactile differentiation options in addition to existing printed decoration options, thereby allowing a choice of attractive decorations and surface effects for the laminated packaging material while still avoiding increased costs.

[0019] Thus, one objective is to enable cost-effective differentiation of the outer layer of a laminated packaging material, i.e., a layer on the outside of the packaging container that will appeal and attract consumers. Such outer layers can be easily interchanged according to the method of the present invention, thereby allowing different decorative and / or tactile features to be laminated to the material according to the different requirements of dairy and filler customers, consumers, and retailers. Such customization allows for the production of separate, short, series of differently decorated, tailored packaging materials without causing downtime, waste, and logistical problems in the main material manufacturing process.

[0020] It is also an objective to correspondingly allow for differentiation opportunities with regard to the inner barrier material by increasing the flexibility in how to swap or add material layers between the inside and outside of the material module while still achieving the required overall packaging laminate mechanical properties to suit the needs of different food products. [Means for solving the problem]

[0021] As a result, some or all of these objectives can be achieved according to the present invention by a method for producing a laminated packaging material, the packaging material obtained by this method, and packaging containers made from this packaging material, as defined in the claims.

[0022] By the term "long-term storage" in the context of the present invention it is meant that the packaging container must be able to preserve the quality, i.e. nutritional value, hygienic safety and taste, of the packed food at ambient conditions for at least 1 or 2 months, such as at least 3 months, preferably for even longer, such as 6 months, for example 12 months or longer.

[0023] By "package integrity" is generally meant the durability of the package, i.e., the resistance of the package to leakage or breakage. A major contributor to this property is good internal adhesion between adjacent layers of laminated packaging material within the packaging laminate. Another contribution comes from the material's resistance to defects such as pinholes, tears, etc. within the material layers, and yet another from the strength of the seal joints where the materials are sealed together during formation of the package. With respect to the laminated packaging material itself, the integrity property consequently focuses primarily on the adhesion of each laminate layer to its adjacent layers and the quality of the individual material layers.

[0024] The term "liquid or semi-liquid food" generally refers to food products that have a flowable content that can optionally contain food particles. Dairy and milk products, soy, rice, grain and seed drinks, juices, nectars, still drinks, energy drinks, sports drinks, coffee or tea drinks, coconut water, green tea drinks, wine, soup, jalapeños, tomatoes, sauces (e.g., pasta sauces), beans, and olive oil are some non-limiting examples of contemplated foods.

[0025] The term "sterile" in relation to packaging materials and containers refers to a state in which microorganisms have been removed, inactivated, or killed. Examples of microorganisms are bacteria and spores. Generally, an aseptic process is used when a product is aseptically packed into a container.

[0026] The term "heat sealing" refers to the process of welding one surface of a thermoplastic material to the surface of another thermoplastic material. A heat-sealable material can create a seal when pressed into contact with another suitable thermoplastic material under appropriate conditions, such as applying sufficient heat and pressure. Suitable heating can be achieved by induction or ultrasonic heating, or other conventional contact or heating means, such as hot air.

[0027] By the term "bulk layer" is usually meant the thickest layer or the layer containing the most material of the multilayer laminate, i.e., the layer that contributes most to the mechanical properties and dimensional stability of the laminate and the packaging container folded from this laminate. In the present specification, "bulk layer" also means the layer that provides the greatest thickness distance in the sandwich structure, and further interacts with the stabilizing facing layers on both sides of the bulk layer, which have a higher Young's modulus, to achieve sufficient such mechanical properties and dimensional stability.

[0028] A "spacer layer" is a layer that creates a predetermined distance or space between very thin material layers. It is a layer with a high Young's modulus and density, such as a high-density, high-tensile stiffness paper layer, foil, or film, positioned on either side of the spacer layer, providing stiffness and stability. The spacer layer has a low or reduced inherent bending stiffness, but does not directly contribute to the bending stiffness of the laminated packaging material itself. It may contribute significantly indirectly, but through interaction with adjacent or laminated layers on both sides, some of the layers may have a high Young's modulus but a small thickness compared to the spacer layer. In a sandwich structure, it is important to have at least one such facing layer or stiffening layer on either side of the spacer layer. When the spacer layer has a very low density and does not contribute any bending stiffness properties by itself, one facing layer on either side of the spacer layer is necessary. Increasing the distance between the facing paper layers also increases the bending strength and bending stiffness of the laminated sandwich structure. The "bulk layer" may comprise a "spacer layer" and additional combined and integrated layers within the bulk layer, but it can also be the same as the spacer layer.

[0029] According to a first aspect of the present invention, there is provided a method for producing a laminated cellulose-based packaging material for liquid or semi-liquid food products, the method comprising the steps of heat sealing into a package having sufficient mechanical strength and barrier properties and an attractive appearance, a) providing a web of bulk material of a central module with a spacer layer of low density cellulose, said web having no inherent bending stiffness or a low bending stiffness of 850 Kg / m 3 Lower density and 60-250g / m 2 and b) providing a web of outer material modules comprising at least one printed substrate layer with or without a decoration printed or applied thereon, the outer material modules being intended to be oriented with the bulk material side of the central module towards the outside of a packaging container made from the laminated packaging material; c) laminating the web of bulk material of the central module and the outer sides of the webs of outer material modules to each other; d) adding decoration to the outer material module; e) providing a web of inner material modules comprising at least a barrier layer, the inner material modules being intended with their bulk material side to be oriented towards the inside of a packaging container made from the laminated packaging material; f) laminating the inner material module web and the inner side of the central module bulk material web to each other; g) applying an outermost transparent and liquid-tight protective layer to the outside of the outer material module; h) applying an outermost thermoplastic liquid-tight and heat-sealable layer to the inside of the outer material module; i) obtaining a resulting web of laminated cellulose-based liquid or viscous food packaging material for further winding onto a reel; The method includes the steps of: a spacer layer forming the center of a sandwich structure within the laminated packaging material; the sandwich structure having at least one paper facing layer arranged on at least one side of the spacer layer and interacting with a further facing layer arranged on the other side of the spacer layer; and the paper facing layer and the further facing layer having a very small thickness but a higher Young's modulus than the spacer layer.

[0030] The steps of this method may be performed in any order, although the order listed above is believed to be preferred from a lamination setup standpoint.

[0031] Low density cellulose spacer layer 750Kg / m 3 Lower, e.g. 700Kg / m 3 The density may be less than 1000 .mu.m.

[0032] Furthermore, the spacer layer has a basis weight of 60 to 250 g / m 2 excluding the printable coating (clay-coat). 2 The stiffness of the liquid carton board may be at least 30% less than the stiffness of a triplex or duplex type liquid carton board having a corresponding basis weight of 100g.

[0033] Thus, a suitable spacer layer has a bending stiffness, excluding the basis weight of the printable coating (clay coat), that is 30 to 100% less than the bending stiffness of a triplex or duplex type liquid carton board at a corresponding basis weight.

[0034] According to a more preferred alternative embodiment, in order to maintain the bending stiffness of the laminated packaging material as high as possible until the moment when the flat packaging material is reshaped into a folded package, the outer and inner material modules must be pre-laminated in separate steps and then laminated to the central module with the spacer layer in a final step. In this way, the lamination operation and the roller pressure applied to the spacer layer are as short and low as possible. Therefore, the idea is to minimize the time and magnitude of the lamination pressure applied to the central part of the material, such as the weaker, less dense spacer layer material.

[0035] In certain embodiments, the outer paper facing layer should be first laminated to the bulk layer to be precut together to create precut holes, apertures, or slits, such as perforations in thick bulky material sections, as is done today in conventional paperboard bulk layers, and such precut holes, apertures, or slits are thus encapsulated between laminate layers, including inner and paper facing layers, metal foils, or barrier-coated films, which are subsequently laminated together.

[0036] When a laminate has a pre-cut hole in the bulk (and in the outer material of the facing layer), a particular advantage of such packaging laminates with a paper facing layer inside the bulk layer is improved openability of the laminated membrane consisting of other laminate layers in the area of ​​the pre-cut hole. The opening device usually has a cut or slit feature, whereby the membrane across the pre-cut hole is cut or broken and opened when twisting / rotating the opening device's cap or screw-on cork or pushing through with a straw. If there is too much resistance to cutting or slitting in the laminated membrane, the opening device of the attached package will be difficult to open, such as when very strong polymer films or layers are used as material layers in the membrane. Also, if there is only low adhesion between the layers of the laminated membrane, there will be peeling and tearing of the material, which will not be very visible after opening. When a facing paper layer is used inside the bulk layer, the laminated film is mechanically stable and has high lamination quality, i.e., there is no tearing or peeling between the layers before and after opening. Furthermore, when the facing paper layer is dense, paper with a compact surface, such as greaseproof paper, is also quite thin and particularly easy to cut or slit open, and appears to have perfect properties against such tearing or slitting or cutting openability. The paper provides stability to the film during lamination, thus resulting in a well-laminated film, and also allows the film to be opened by the opening device during cutting. Therefore, the cut is clean, provides a regular cut edge, and is easy to open by turning the screw cork without excessive resistance.

[0037] The laminated packaging material obtained by the method of the present invention is therefore a three-part modular sandwich material comprising a cellulose-based spacer layer and at least one mechanically stabilized facing layer of a relatively thin, high-density paper layer on one side of the spacer layer, the laminate further comprising functional layers with various barrier and heat-sealing properties.

[0038] In one embodiment, the spacer layer creates a distance or space between very thin layers of material, which have a high Young's modulus and density, such as high-density paper layers, i.e., layers that provide stiffness and stability, so-called facing layers, positioned on either side of the spacer layer. Although additional layers according to this invention can be positioned on either side of the spacer layer to contribute to the overall sandwich structure, we will primarily discuss the paper facing layers in this context. The spacer layer may have low or no inherent bending stiffness and therefore does not directly contribute to the bending stiffness or strength of the laminated packaging material itself. However, indirectly, the spacer layer may contribute significantly through interactions with adjacent or laminated layers on either side, some of which may have a high Young's modulus but a small thickness compared to the spacer layer. In a sandwich structure, it is important to have at least one such facing layer, or a stiffening layer on either side of the spacer layer. If the spacer layer has a very low density and does not contribute any bending stiffness properties on its own, one paper facing layer on either side of the spacer layer is required. When the distance between facing layers of paper is increased, the mechanical strength and bending stiffness of the laminated sandwich structure also increases.

[0039] A suitable cellulose-based material for the spacer layer can be, for example, so-called foamed cellulose, i.e., foamed fibrous cellulose, which is a fibrous material with an adjustable density and can be produced by a foam-forming process.

[0040] Thus, the bulk layer comprising foamed cellulose may have a density of, for example, 100 to 600 kg / m 3 , e.g. 100~500Kg / m 3 , e.g. 200~500Kg / m 3 , for example, 200 to 400 kg / m 3 , for example 300~500Kg / m 3 , for example 300~400Kg / m 3 etc., 700Kg / m3 The lower the density of the foamed cellulose layer, the more cost-effective it is in terms of raw materials consumed, while the better resistance to thickness loss of the foamed cellulose is characterized by a density of 700 Kg / m 3 According to one embodiment, the optimum density of the foamed cellulose used in the laminated packaging material is 300 to 500 kg / m 3 , especially 300~400Kg / m 3 It was concluded that:

[0041] Thus, the method of the present invention allows the incorporation of foamed cellulose bulk material into a laminated packaging material suitable for preparing packaging containers for food products, particularly liquid and semi-liquid foods. Lamination of such bulk layers to polymer layers can be carried out by melt extrusion operations, such as extrusion coating and extrusion lamination of polymer layers. Extrusion is typically carried out at high temperatures, up to about 330°C in the case of molten low-density polyethylene. Such temperatures have not been a significant problem for bulk layers comprising foamed cellulose, as opposed to other foamed polymer layers. Foamed cellulose, contrary to foamed polymer layers in general and foamed polyolefins in particular, is fairly thermally stable above 300°C and has low thermal conductivity. 300-400 kg / m 3 It has been found that at a relatively low density of 0.15 mm, the foamed cellulose does not lose significant thickness in the extrusion lamination operation and maintains sufficient peel strength, or so-called z-strength, for use in packaging laminates for the purposes of the present invention.

[0042] Bulk layers comprising foamed cellulose as described in aspects and embodiments herein further provide desirable peel strength, i.e., bulk layers comprising foamed cellulose do not easily peel under standard conditions. Peel strength is measured, for example, in J / m according to TAPPI T569. 2 The bonding energy can be measured by a Huygen Internal Bonding Energy tester, which provides values ​​of 60 to 300 J / m2 , e.g., 60 to 250 J / m 2 , e.g., 80 to 200 J / m 2 , e.g., 140-200 J / m 2 etc. In some aspects and embodiments, the bulk layer provides distance between the barrier layer and the outermost thermoplastic decorative layer, thereby allowing for a tailored laminated packaging construction. In some embodiments, the bulk layer comprising foamed cellulose provides peel strength in combination with compressive strength in the thickness direction (Z- or ZD) while providing sufficient distance between the barrier layer and the decorative layer.

[0043] Foamed cellulose can be produced by mixing cellulose fibers with a foaming fluid such as water, and optionally a surfactant such as sodium dodecyl sulfate (SDS). The amount of surfactant is 0.1 wt% to 20 wt%, e.g., 0.5 wt% to 10 wt%, e.g., 1 wt% to 5 wt%, e.g., 1.5 wt% to 3 wt%, etc. A rotor mixer on a typical foam generator produces foamed cellulose. Foams are typically formed by introducing a gas into the mixer. Air is an example of a suitable gas. Another suitable gas is oxygen. Typically, the gas is introduced into the mixture by pressurized gas and by a vortex created by stirring. Typically, the cellulose is provided as a liquid dispersion comprising cellulose fibers. An example of the liquid is water. Some examples of cellulose fibers are cellulose-based fibers such as chemical pulp fibers, chemi-thermomechanical pulp fibers, thermo-mechanical pulp fibers, and kraft pulp fibers. The fiber dispersion can be added to the foaming fluid, for example, after the foam is generated by the fluid (including the surfactant). Optionally, the liquid dispersion containing cellulose fibers can be combined with the foaming fluid prior to foaming. Additives can be added as needed to control the consistency of the foam. The foamed cellulose produced as described herein passes through a nozzle arrangement ("headbox") where pressure and foam formers produce a foamed cellulose web, which is at least partially dried and then wound onto a rail and stored before preparation for future use, e.g., packaging material. Optionally, the foamed cellulose web can be used in-line, i.e., additional layers can be applied directly to transform the foamed cellulose web into a laminated packaging material for packaging liquid or semi-liquid foods. Compared to traditional paper manufacturing, additional or modified drying can be advantageously used to achieve the desired dryness and density.

[0044] In some embodiments, the foamed cellulose can be mixed with other materials, such as additives, and / or microfibrous cellulose, and / or refined pulp, and / or strengthening chemicals or agents, such as starch and its derivatives, mannogalactans, carboxymethyl cellulose, melamine-formaldehyde colloid, urea-formaldehyde resin, polyamide-polyamine-epichlorohydrin resin.

[0045] Another example of a spacer layer is made from so-called containerboard material, which typically has a very high density but low inherent bending stiffness and differences in other mechanical properties, such as dimensional and mechanical stability, compared to existing liquid packaging paperboard; therefore, the integrity and barrier properties of a package made from a laminate having a bulk layer of such material would be compromised when made by conventional manufacturing of packaging laminates.

[0046] In particular, the containerboard layer itself has a substantially lower bending stiffness compared to laminated packaging materials suitable for liquid packaging. Generally, fluting material has a higher bending stiffness per basis weight than linerboard material.

[0047] Bending stiffness is not typically measured for containerboard material because it is intended anyway for corrugated carton production, but such material, excluding the basis weight of the printable coating (clay coat), has been measured to have a bending stiffness at a corresponding basis weight that is at least 30%, such as at least 40%, such as at least 50% lower than the bending stiffness of liquid carton paperboard. However, the containerboard still contributes to the overall mechanical properties and bending stiffness of the laminated packaging material by also providing a distance layer with a high Young's modulus between opposing plies in the sandwich structure, and by having greater compressive strength properties in the plane (x-y) of the layers than conventional paperboard for liquid packaging.

[0048] Containerboard is also known as corrugated case material (CCM), and the material required for corrugated case material is corrugated media (or fluted media) that, during use, is grooved (welded) and then placed by gluing between two flat linerboards or liner media. Such a corrugated configuration provides high bending stiffness of the sandwich structure due to the grooved middle layer acting as a spacing or spacer layer between the two relatively thin liner layers. Thus, the two types of paper that make up containerboard are linerboard material, commonly referred to as kraftliner or testliner, and fluted (or corrugated media) material.

[0049] The two types of paper that make up containerboard are linerboard and fluting (or corrugated media) stock. Containerboard is made primarily from natural, unbleached cellulose fibers, so its shape can vary depending on the type of cellulose, but it is generally brown or beige in color. However, white top linerboard also exists, which has a white top layer on one side, and this top linerboard is usually a more expensive material.

[0050] Linerboard is typically 835 kg / m 3 etc., 850kg / m 3 It has a lower density, is brown or beige in color and comprises mainly softwood fibers, such as spruce and pine fibers.

[0051] Therefore, fluting is usually a corrugated type with a maximum load capacity of 600 to 750 kg / m 3 , e.g. 600-700 kg / m 3 , usually about 650 kg / m 3Fluting paper is used as a corrugating medium in container boards having densities such as 1000-12000 and 1250-14000. Fluting paper is brown or beige in color, contains mostly short fibers, and is generally a very low-cost, low-quality paper, much like linerboard, that is not suitable as such for liquid carton packaging. However, when used as a spacer layer in sandwich constructions, it works well for that purpose at a substantially lower cost if it is of the approved type and is combined in the proper manner with the appropriate layers in such packaging laminates.

[0052] However, fluting media may form a spacer layer, or a non-fluted spacer layer, by being a low-stiffness, low-cost fibrous material that can provide sufficient distance in the sandwich structure for the laminated liquid carton packaging material. Fluted spacer layers, i.e., shapely spacer layers, are not within the scope of this invention. Corrugated carton materials may bring entirely different technical implications and requirements for the laminated liquid carton packaging material and will not be discussed here.

[0053] Fibers commonly used in the manufacture of containerboard materials can be broadly divided into two main types: recycled fibers and new, or virgin, fibers. Paper properties depend on the structural characteristics of the various fibers comprising the sheet. Generally, the higher the virgin fiber content, the stronger and stiffer the fluting or linerboard material. The fluting material investigated for the purposes of this invention is semi-chemical fluting from power flute, consisting of 100% primary fibers made from hardwoods, such as birch. Birch is an optimal fluting raw material. Its structure contains a high concentration of lignin and hemicellulose. The pulping process inevitably retains the highly hydrophobic lignin and modifies the remaining hemicellulose so that the soft, flexible cellulose core of the fiber is protected. This provides higher stiffness and creep properties. When used for liquid packaging, commercially available fluting materials need to be supplemented with one or more additional sizing materials during pulping or cellulosic web production to handle the liquid and high-humidity conditions for this new use and application. Conventional sizing techniques and chemicals (AKD, ASA, resins, etc.) can be used on the fluting material to meet the necessary requirements for a particular product.

[0054] Linerboard made from virgin fibers is called kraft liner, while linerboard made from recycled fibers is known as test liner. A mixture of virgin and recycled fibers is also possible. Kraft linerboard must have at least 80% virgin fiber by weight, preferably 100% virgin fiber by weight. The fibers used for linerboard are longer than those used for fluting material, and because linerboard is primarily intended for the outer liner layer of carton material, the fibers are sized with sizing material to withstand different humidity and wet conditions.

[0055] Thus, containerboard materials have a lower bending stiffness than corresponding paperboards for liquid packaging, but on the other hand have a higher SCT index, i.e. a higher SCT value per basis weight in the machine direction, than conventional liquid paperboard materials or than other paper or cellulose materials suitable in this context. Typically, containerboard has a bending stiffness at least 30% lower than that of liquid paperboard of a corresponding basis weight, excluding the basis weight of the printable coating (clay coat). Fluting materials generally have a higher bending stiffness per basis weight than linerboard materials.

[0056] The SCT value is a property measured by the international standard ISO 9895 and is relied upon to compare different containerboards with each other. The SCT or Short Compression Test measures the internal compression resistance of the paper fibers, i.e., the compressive strength within the plane of the paper in the CD and MD. This property varies depending on the basis weight of the particular paper being measured.

[0057] Packages made from materials with a higher SCT index have better stackability, which is a measure of the compressive strength per basis weight in the plane of the carton material (x-y plane). Containerboard materials typically have an SCT index greater than 30 Nm / g in the MD, thus providing the required compressive strength and stackability for liquid paperboard laminates. These materials do not need to be optimized for stiffness properties because they are used only as (non-grooved) spacer layers in laminated materials for liquid carton packaging. Therefore, while such linerboard materials are primarily intended for facing layers in corrugated carton sandwich structures, for the purposes of this invention, they are used as spacer layers in laminated structures with additional laminated facing layers on either side to provide the required stiffness for the laminated material of the liquid carton.

[0058] For comparison, today's liquid paperboard materials have an SCT index of about 25 Nm / g, but because they are relied upon as the primary provider of dimensional stability in the laminated packaging material of liquid cartons, they are also optimized with respect to all other properties. When replacing today's optimized liquid paperboard with a low-cost spacer layer in a sandwich structure in the laminate, such a spacer layer would need to have a higher SCT index, above 30 Nm / g, to offset the loss of properties upon removal of the state-of-the-art paperboard.

[0059] Since the new spacer layer is laminated to a further facing layer in a sandwich configuration in a laminate structure, it is not necessary to provide a white or smooth (e.g. clay coated) printed surface on the spacer layer itself, and in that respect containerboard material is a suitable material for such a spacer layer.

[0060] In terms of moisture resistance, these materials are recommended to be used at 35 g / m² to perform better in liquid carton packaging laminates. 2 The Cobb water absorption value can be lower. The Cobb value, measured according to ISO 535, is already met by most linerboard materials, but some fluted materials may require additional sizing for use as unfluted spacer layers in liquid carton packaging laminates. Therefore, the containerboard material in the bulk layer is provided with at least one sizing additive.

[0061] In further embodiments, the spacer layer can comprise a combination of different cellulose or paper types. When the spacer layer comprises foamed cellulose, the portion of foamed cellulose is at least 20% of the thickness of the bulk layer, such as at least 25%, for example at least 30%, for example at least 40%. This percentage can be determined by observing a cross-section of the packaging material under a microscope.

[0062] In yet another embodiment, the bulk layer may consist primarily of the spacer layer, but may further comprise one or two integrated paper layers having a relatively higher Young's modulus but a smaller thickness than the spacer layer to provide some bending strength and bending stiffness to the final laminated material produced.

[0063] The final laminated material thus comprises at least one such relatively thinner, stiffer paper disposed on either side of the spacer layer. In such a configuration, the thinner, stiffer paper acts similarly to the flanges of an I-beam structure or the facing layers of a sandwich structure, thus mechanically stabilizing the sandwich, for example, with respect to bending stiffness and in-plane compressive strength in various directions within the material.

[0064] Suitable such paper facing layers can be found in thin kraft, greaseproof or parchment paper, e.g., 30-70 g / m 2 , for example 30 to 60 g / m 2 etc., 20~100g / m 2 Basis weight and 600~1500kg / m 3 It has a density of

[0065] Typically, the facing layer of paper should have a Young's modulus of 1 to 10 GPa, for example 5 to 10 GPa.

[0066] The paper facing layer can be included in the laminated material structure in different ways. For example, when the spacer layer has a higher density and inherent stiffness, such as a spacer layer of containerboard material, the bulk material layer can comprise a containerboard material layer and a thinner, stiffer, or denser paper facing layer on one side of the spacer layer. As a result, it may be sufficient for the final laminated material to have only one paper facing layer on one side and a less stable facing layer of a different material, such as an oriented plastic film, on the other side of the spacer layer. Alternatively, the paper facing layer can be included in one of the inner or outer material modules that are laminated to the fluting material layer.

[0067] The bending stiffness of a packaging material laminate can be derived from the thickness and Young's modulus of the individual layers. To match the mechanical properties of a sandwich structure of laminated materials, the facing layers of the sandwich should be placed on either side of the spacer layer so that they have substantially equal extensional stiffness. The extensional stiffness is given by the product of Young's modulus and thickness. This can be adjusted by varying the thickness and Young's modulus of the paper, and if there is more than one such paper facing layer on either side of the spacer layer, it is possible to calculate the total bending stiffness of that particular combination of facing layers.

[0068] Various specific embodiments are contemplated by the present invention. The bulk material has a density of 600-700 kg / m 3 Alternatively, the bulk material may comprise a spacer layer of fluting with a density of 600-700 kg / m, while the outer material module comprises a facing layer of paper. Alternatively, the bulk material may comprise a spacer layer inside the spacer layer and an integrated facing layer of paper, the spacer layer having a density of 600-700 kg / m. 3 This is the so-called fluting, which has a density of 1000 .mu.m.

[0069] By tailoring the sandwich structure so that the outer thicker paper facing layer can be separated from the spacer layer, while allowing for differentiation of the printing background color, texture, and pattern, and the printed substrate layer has as thin as possible, but higher Young's modulus barrier coated substrate paper for lamination in the inner material module, the efficiency of the barrier coating process can also be increased by using thinner substrate and therefore fewer rolls of substrate in, for example, a vacuum coating process. The asymmetry of the properties of the paper facing layer can be balanced by other layers in the structure, so that symmetry about the centerline of the spacer layer (vs.) can still be obtained and curling can be avoided.

[0070] In one embodiment where the bulk layer comprises foamed cellulose, the final laminated material comprises one paper facing layer disposed on each side of the spacer layer to provide sufficient stability to the final laminated packaging material.

[0071] In one embodiment, the bulk material comprises a spacer layer and an integrated paper facing layer on a first side (inner side) of the spacer layer, while the outer material module also comprises a paper facing layer laminated to a second side (outer side) of the bulk and the spacer layer. In yet another embodiment, the bulk material layer comprises a spacer layer and an integrated paper facing layer on a second side of the spacer layer, while the inner material module also comprises a paper facing layer laminated to the bulk and the first side of the spacer layer.

[0072] In a further embodiment, the bulk material comprises a spacer layer and a facing layer of one consolidated paper on either side of the spacer layer.

[0073] In different embodiments, the bulk material comprises one spacer layer or a combination of two or more different spacer layers, while the inner and outer material modules laminated to the first and second sides of the bulk layer comprise facing layers of paper, respectively, or oriented polymer film.

[0074] In a particular embodiment, the spacer layer is a fibrous layer made by a foam forming process and has a density of 150 g / m 2 and a thickness of 600 μm, and 2 , e.g. 70g / m 2 and the like.

[0075] According to one embodiment, the outer material module comprises a facing layer of paper having a printable or printed surface oriented towards the outside of the module and laminated to the outer surface of the bulk material with an intermediate bonding layer or adhesive.

[0076] In yet another embodiment, the outer material module is a polymer film having a printable or printed surface that is laminated to the outer surface of the bulk material with an intermediate bonding layer or adhesive.

[0077] In a further embodiment, the outer material module comprises a polymer film having a printable or printed surface and a facing layer of paper to which is further laminated a polymer film, and the module is laminated to the outer surface of the bulk material with an intermediate bonding layer or adhesive.

[0078] By removing at least some of the decorative function and bending stiffness of today's bulk layer, i.e., the white printable surface onto which a colored decorative pattern can be printed, from the bulk layer and instead laminating a lower-quality bulk layer to the outside of the bulk layer with another printed substrate layer, great flexibility in the manufacturing process of different-looking packaging laminates can be provided at low cost and with short lead times from order to delivery. This makes it easy to change the appearance of a packaging container without affecting the manufacturing process or raw materials other than simply changing the printed substrate and the actual printed decorative pattern. The printed substrate layer can be white, brown, colored, metalized, etc. At the same time, the overall sandwich effect of the laminate layers still results in a mechanically and dimensionally stable packaging container with a good appearance.

[0079] In one embodiment, the inner material module comprises a facing layer of paper having a barrier coating, laminated to the inner surface of the bulk material by an intermediate bonding layer or adhesive.

[0080] In another embodiment, the inner material module is a polymer film having a barrier coating that is laminated to the inner surface of the bulk material by an intermediate tie layer or adhesive.

[0081] In a further embodiment, the inner material module comprises a polymer film and a facing layer of paper to which the polymer film is further laminated, the film or paper having a barrier coating, and the module is laminated to the inner surface of the bulk material by an intermediate bonding layer or adhesive.

[0082] In yet another embodiment, the inner material module comprises aluminum foil.

[0083] Therefore, the inner distinction of the barrier function can also be varied depending on how the central and outer material modules are matched and on the requirements of the food product being packaged.

[0084] Suitable printing substrate polymer films may be pre-fabricated, stretched stabilized polymer films selected from the group consisting of films based on any of the above polymers or mixtures thereof, or multilayer films having a surface layer comprising any of the above polymers or mixtures thereof. The pre-fabricated, stretched stabilized polymer films may be selected from the group consisting of polyesters such as polyethylene terephthalate (PET), oriented or unoriented PET (OPET, BOET), oriented or unoriented polyethylene furanoate (PEF), oriented or unoriented polybutylene terephthalate (PBT), polyethylene napthanate (PEN), for example, unoriented or oriented polyamides (PA, OPA, BOPA), polyamides such as ethylene vinyl alcohol copolymer (EVOH), polyolefins such as polypropylene, oriented uniaxially oriented polypropylene or biaxially oriented polyethylene (PP, OPP, BOPP), polyethylenes such as oriented or unoriented high density polyethylene (HDPE), linear low density polyethylene (LLDPE), and cycloolefin copolymers (COC), as well as mixtures of any of these polymers.

[0085] In a further embodiment, the printing substrate has a printable surface that is a clay-coated white paper surface, or a metallized film or paper surface.

[0086] The outer material module is 0.5 to 4 g / m 2 , e.g., 1 to 3 g / m 2 The aqueous adhesive component can be applied in equal amounts to one of the surfaces to be bonded to each other and then laminated to the bulk material by pressing them together.

[0087] The inner material module is 0.5 to 4 g / m 2 , e.g., 1 to 3 g / m 2 The aqueous adhesive component can be applied in equal amounts to one of the surfaces to be bonded to each other and then laminated to the bulk material by pressing them together.

[0088] The final laminated packaging material of the present invention typically does not contain aluminum foil as a barrier material. If aluminum foil is included in the first pre-laminated material on the first side of the bulk layer, it will essentially add some rigidity and mechanical strength to the final sandwich structure, i.e., the final laminated packaging material. However, assuming that future packaging materials aim to reduce carbon dioxide consumption in production and thereby eliminate or reduce the content of aluminum barrier materials, i.e., so-called foil-free laminated packaging materials, in laminates based on bulk layers with spacer layers made of foamed cellulose, which has a significantly lower density and bending stiffness than today's liquid packaging paperboard, facing layers of mechanically stabilized paper on both sides of the spacer layer would be a better choice for the laminated structure. Furthermore, the symmetrical arrangement with facing layers of paper on both sides of the spacer layer is advantageous because it reduces increased curling of the laminated packaging material with increased moisture content and further improves the compressive strength of packages made from the material, i.e., there are fewer "warped" packages from stacked packages on top of each other during transportation and distribution on pallets.

[0089] Various methods and laminating materials can be used in laminating the two webs of the bulk layer of the inner and outer material modules to the web. Melt-extrusion lamination with a molten thermoplastic bonding polymer in between is described above and is a common method for laminating two webs to each other. In one embodiment of the present invention, the surfaces to be laminated to each other are all paper- or cellulose-based surfaces, resulting in good adhesion between the laminated surfaces. Some types of surfaces may require oxidative pretreatment of the surface before bonding to other surfaces, or alternatively, or in addition, the melt-extruded bonding polymer may comprise at least a portion of an adhesive thermoplastic polymer, i.e., a polymer with functional groups, typically carboxyl or maleic anhydride groups, that have an affinity for various surfaces.

[0090] Suitable adhesive polymers for the inner side of the laminated material, i.e. for the bonding layer between the outer heat-sealable layer and the barrier layer or primer-coated substrate layer, or for bonding to the bulk layer of the barrier film in one or more such bonded laminate layers, are so-called adhesive thermoplastic polymers, such as modified polyolefins, mostly based on LDPE or LLDPE copolymers, or graft copolymers with functional groups containing monomer units, such as carboxyl or glycidyl functional groups, such as (meth)acrylic acid monomers or maleic anhydride (MAH) monomers (i.e. 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 or adhesive polymers are so-called ionomers or ionomeric polymers. Preferably, the modified polyolefin is ethylene acrylic acid copolymer (EAA) or ethylene methacrylic acid copolymer (EMAA).

[0091] A corresponding modified polypropylene-based thermoplastic adhesive or tie layer may also be beneficial depending on the requirements of the finished package.

[0092] Such adhesive polymer layers or tie layers are usually applied together with the respective outer layer or additional bulk-barrier tie layer in a co-extrusion coating operation.

[0093] The adhesive can be applied as an aqueous adhesive solution or composition, applied to one of the surfaces to be laminated together, and then joined to the other surface in a lamination station containing one or more lamination roller nips. Preferably, there should be only one lamination nip in the lamination station to apply as little pressure as possible to the weak, low-density spacer layer. However, several consecutive nips may be advantageous in some embodiments by applying low pressure in several consecutive roller nips or in one wide nip to enhance adhesion.

[0094] Thus, laminated packaging materials can have a high fiber content and materials from renewable sources, which is advantageous from an environmental standpoint. Furthermore, an increased cellulose fiber content in the material can make it easier to process during the recycling process, especially when the ratio of the amount of thermoplastic polymer layer to aluminum foil can be simultaneously reduced. This is an advantageous effect when laminating cellulose-based modules using aqueous adhesive absorption lamination, i.e., a lamination method in which only a very small amount of polymer adhesive is applied to bond the two surfaces to be laminated together, while the aqueous medium or solvent is absorbed into the cellulose fiber network of the laminated layers, and no additional drying or heating is required. In this way, the number of layers of paper or cellulose-based material can be increased, while less thermoplastic bonding material is required, such as with melt extrusion lamination, and the barrier layer can be made thinner due to the effective combination of the properties of the various material layers contained in the laminated packaging material.

[0095] Suitable thermoplastic polymers for the outermost and innermost heat-sealable, liquid-tight layers of the laminated packaging material of the present invention are preferably polyolefins, such as homopolymers or copolymers of polyethylene and polypropylene, more preferably low-density polyethylene (LDPE), linear LDPE (LLDPE), single-site catalyst metallocene polyethylene (m-LLDPE), and mixtures or copolymers thereof. According to a preferred embodiment, the outermost heat-sealable, liquid-tight layer is LDPE, while the innermost heat-sealable, liquid-tight layer is a blend of m-LLDPE and LDPE for optimal lamination and heat-sealing properties. The outermost and innermost thermoplastic polymer layers can be applied to the desired thickness by (co)extrusion coating of molten polymer. According to another embodiment, the outermost and / or innermost liquid-tight, heat-sealable layer can be applied in the form of a prefabricated oriented or non-oriented film.

[0096] According to yet another embodiment, the outermost heat-sealable, liquid-tight and protective thermoplastic polymer layer can be applied by an aqueous dispersion coating of a thermoplastic polymer, such as when only a thin thickness of such outermost layer is desired or when such a process is preferred for other reasons.

[0097] The same thermoplastic polyolefin-based materials, particularly polyethylene, as listed above for the outermost and innermost layers are also suitable for the interior, bulk or core layer of the laminated material, i.e., the bonding layer between the paper or paperboard or the like and a previously laminated material containing a barrier film or other film layer.

[0098] Thus, suitable barrier layers include film or paper substrates having a barrier coating, such as a dispersion coated or liquid film coated barrier coating, or a vapor deposited barrier coating.

[0099] Suitable film substrates for such barrier films may be polymer films selected from the group consisting of polyesters such as polyethylene terephthalate (PET), oriented or unoriented PET (OPET, BOET), oriented or unoriented polyethylene furanoate (PEF), oriented or unoriented polybutylene terephthalate (PBT), polyethylene napthanate (PEN), polyamides such as unoriented or oriented polyamides (PA, OPA, BOPA), ethylene vinyl alcohol copolymers (EVOH), polyolefins such as polypropylene, uniaxially oriented polypropylene or biaxially oriented polyethylene (PP, OPP, BOPP), polyethylenes such as oriented or unoriented high density polyethylene (HDPE), linear low density polyethylene (LLDPE), and cycloolefin copolymers (COC), as well as films based on any of the mixtures of any of these polymers, or multilayer films having a surface layer comprising any of the aforementioned polymers or mixtures thereof.

[0100] Barrier properties can be provided by a single polymer layer or layers, or a film made of one or more barrier polymers, while in other embodiments, the film polymer serves only to provide a substrate for a subsequently applied barrier coating. The most important barrier property in sterile, long-term packaging is oxygen barrier properties. Therefore, oxygen barrier properties are further provided by a thin liquid film coating, e.g., a barrier polymer coated onto the substrate in the form of a dispersion or solution in a liquid medium or solvent and then dried into a thin barrier coating. It is important that the dispersion or solution be homogeneous and stable to result in a uniform coating with uniform barrier properties. Examples of suitable polymers for aqueous compositions are polyvinyl alcohol (PVOH), water-dispersible ethylene vinyl alcohol (EVOH), or polysaccharide-based water-dispersible or soluble polymers. Such dispersion-coated, or so-called liquid film-coated (LFC) layers can be very thin, down to a tenth of a gram per square meter, providing a high-quality, uniform layer, provided the dispersion or solution is homogeneous and stable, i.e., well prepared and mixed. PVOH has excellent oxygen barrier properties under dry conditions and also provides very good odor barrier properties, i.e., the ability to prevent odorous substances from entering the package from the surrounding environment, e.g., a refrigerator or storage room, which is important during long-term storage of the package. Furthermore, such liquid film coated polymer layers, consisting of water-dispersible or water-soluble polymers, provide good internal adhesion to adjacent layers, which contributes to good integrity of the final package.

[0101] Preferably, the polymer is a polymer selected from the group consisting of vinyl alcohol-based polymers such as PVOH or water-dispersible EVOH, acrylic or methacrylic acid-based polymers (PAA, PMAA), such as starch or starch derivatives, cellulose nanofibers (CNF), nanocrystalline cellulose (NCC), chitosan or other cellulose derivatives, hemicellulose, polysaccharides such as water-dispersible polyvinylidene chloride (PVDC) or water-dispersible polyesters, or a combination of two or more thereof.

[0102] More preferably, the polymer binder is selected from the group consisting of PVOH, water-dispersible EVOH, acrylic or methacrylic acid-based polymers (PAA, PMAA), polysaccharides such as starch or starch derivatives, chitosan, or other cellulose derivatives, or a combination of two or more thereof.

[0103] Such barrier polymers are therefore suitably applied by a liquid film coating process, i.e., in the form of an aqueous or solvent-based dispersion or solution, which upon application is spread in a thin, uniform layer onto the substrate and then dried.

[0104] Water-based compositions generally have certain environmental advantages, and preferably, the liquid gas barrier composition is water-based, as such compositions typically have better working environment integrity than solvent-based systems.

[0105] As briefly mentioned above, a polymer or compound having carboxylic acid functionality can be included to improve the water vapor and oxygen barrier properties of the PVOH coating. Preferably, the polymer having carboxylic acid functionality is selected from ethylene acrylic acid copolymer (EAA) and ethylene methacrylic acid copolymer (EMAA), or a mixture thereof. One particularly preferred barrier layer mixture comprises PVOH, EAA, and a lamellar inorganic compound. The EAA copolymer is then included in the barrier layer in an amount of about 1 to 20 wt. % based on the dry coating weight. Other examples of polymer binders that provide oxygen barrier properties suitable for liquid film coatings are polysaccharides, particularly starch or starch derivatives, such as, preferably, oxidized starch, cationic starch, and hydroxypropylated starch. Examples of such modified starches include hypochlorite oxidized potato starch (Raisamyl 306 from Raisio), hydroxypropylated corn starch (Cerestar 05773), and the like. However, other forms of starch and polysaccharide derivatives can also provide gas barrier properties to some extent.

[0106] However, most preferably, the gas barrier polymer is PVOH, as PVOH has all the good properties mentioned above, namely film forming properties, gas barrier properties, cost effectiveness, food compatibility, and odor barrier properties.

[0107] PVOH-based gas barrier compositions exhibit their pore-cleaning capabilities when the PVOH has a degree of saponification of at least 98%, preferably at least 99%, although PVOH with lower degrees of saponification also provide oxygen barrier properties.

[0108] According to one embodiment, the liquid composition further comprises inorganic particles to further improve the oxygen gas barrier properties.

[0109] The polymer binder material can be mixed with inorganic compounds formed, for example, in lamellar or flake form. The layered arrangement of the flake-shaped inorganic particles causes oxygen gas molecules to travel a tortuous path through the oxygen barrier layer, a longer distance than the normal straight path across the barrier layer.

[0110] The lamellar inorganic compound is a so-called nanoparticle compound dispersed in an exfoliated state, i.e., the lamellae of the layered inorganic compound are separated from each other by a liquid medium. Therefore, the layered compound can be preferably swollen or cleaved by a polymer dispersion or solution, and the polymer penetrates the layered structure of the inorganic material during dispersion. Furthermore, the layered compound is swollen with a solvent before being added to the polymer solution or dispersion. Therefore, the lamellar inorganic compound is dispersed in an exfoliated state in the liquid gas barrier composition and the dried barrier layer. Preferred nanoparticles are nanoparticles of montmorillonite, such as purified montmorillonite or sodium-exchanged montmorillonite. Nano-sized lamellar inorganic compounds or clay minerals can have an aspect ratio of 50 to 5000 and a size of up to about 5 mm in an exfoliated state.

[0111] Suitable inorganic particles consist primarily of such lamellar bentonite particles having an aspect ratio of 50-5000.

[0112] The barrier layer may comprise about 1% to about 40% by weight, more preferably about 1% to about 30% by weight, and most preferably about 5% to about 20% by weight of the lamellar inorganic compound based on the weight of the dried coating. If the total amount is too low, the gas barrier properties of the coated and dried barrier layer will not be significantly improved compared to when no lamellar inorganic compound is used. If the total amount is too high, the liquid composition will be more difficult to apply as a coating and will be more difficult to handle in the storage tank and conduits of the applicator system. Preferably, the barrier layer comprises about 99% to about 60% by weight, more preferably about 99% to about 70% by weight, and most preferably about 95% to about 80% by weight of the polymer based on the weight of the dried coating. Additives, such as dispersion stabilizers or the like, may be included in the gas barrier composition, preferably in a total amount of about 1% by weight or less based on the weight of the dried coating. The total dry content of the composition is preferably 5 to 15% by weight, more preferably 7 to 12% by weight.

[0113] According to a different preferred embodiment, the inorganic particles consist primarily of lamellar talc particles with an aspect ratio of 10 to 500. The composition can comprise 10 to 50 wt. % of talc particles, more preferably 20 to 40 wt. % of the talc particles, based on the dry weight. Less than 20 wt. % does not significantly increase the gas barrier properties, while more than 50 wt. % weakens the internal cohesion between the particles in the layer, making the particle-coated layer more brittle and prone to breakage. The polymer binder is likely too scarce to surround and disperse the particles, laminating them against each other within the layer. The total dry content of such a liquid barrier composition from PVOH and talc particles can be 5 to 25 wt. %.

[0114] Good oxygen barrier properties can be achieved when colloidal silica particles are used that exhibit a size of 3 to 150 nm, preferably 4 to 100 nm, and even more preferably 5 to 70 nm, and these particles are preferably amorphous and spherical. The use of colloidal silica particles has the further advantage that the liquid barrier composition can be applied at a dry content of 15 to 40 wt. %, preferably 20 to 35 wt. %, and even more preferably 24 to 31 wt. %, thereby reducing the need for forced drying.

[0115] Alternatives to inorganic particles according to the present invention are particles of kaolin, mica, calcium carbonate, and the like.

[0116] A preferred polymer binder when inorganic particles are employed to provide oxygen barrier properties is PVOH, due in part to its advantageous properties described above. Additionally, PVOH is advantageous from a mixing standpoint, i.e., PVOH generally readily disperses or exfoliates inorganic particles in aqueous solutions of PVOH, forming a stable mixture of PVOH and the particles, thus allowing for a well-coated film with uniform composition and morphology.

[0117] The oxygen gas barrier layer has a dry weight of 0.1 to 5 g / m 2 , preferably 0.5 to 3.5 g / m 2 , more preferably 0.5 to 2 g / m 2 A total amount of 0.5 g / m 2 Less than this will not have any effect in further filling and sealing the porous substrate surface and will not have any gas barrier properties, while 5 g / m 2 Above this level, the coated layer is unlikely to provide any cost-effectiveness to the packaging laminate due to the generally high cost of the barrier polymer and the high energy cost of evaporating the liquid. Appreciable levels of oxygen barrier are found above 0.5 g / m². 2 A good balance of barrier properties and cost can be achieved with PVOH in the range of 0.5 to 3.5 g / m 2 This is achieved by:

[0118] The oxygen gas barrier layer can be applied as two part-layers in two successive steps with an intermediate drying step. When applied as two part-layers, each layer has a density of 0.1 to 2.5 g / m 2 , preferably 0.5 to 1 g / m 2 The two partial layers are preferably applied in an amount of 0.5 to 2 g / m, allowing for a high-quality overall layer from a smaller amount of liquid gas barrier composition. 2 Preferably, each of these is 0.5 to 1 g / m 2 can be applied in an amount of

[0119] An additional barrier layer can be applied to a substrate surface, such as a dense paper substrate or film material, by physical vapor deposition (PVD) or chemical vapor deposition (CVD). The substrate material itself can also contribute several properties, but above all it should have suitable surface properties to accept the vapor deposition coating and should work efficiently in the vapor deposition process.

[0120] Thin vapor-deposited layers are typically only nanometer thick, i.e., have a thickness on the order of nanometers, for example, 1 to 500 nm (50 to 5000 Å), preferably 1 to 200 nm, more preferably 1 to 100 nm, and most preferably 1 to 50 nm.

[0121] One common type of vapor deposited coating that often has some barrier properties, particularly water vapor barrier properties, is the so-called metallized layer, for example a metallic aluminum physical vapor deposition (PVD) coating.

[0122] Such vapor-deposited layers consist essentially of metallic aluminum and can have a thickness of 5-50 nm, which corresponds to less than 1% of the metallic aluminum material present in conventionally thick aluminum foil for packaging, i.e., 6.3 mm. Vapor-deposited metal coatings require significantly less metal material, but at best offer only low levels of oxygen barrier properties and must be combined with additional gas barrier materials to impart sufficient barrier properties to the final laminate material. On the other hand, they can complement additional gas barrier layers, but do not have water vapor barrier properties and are rather susceptible to moisture.

[0123] Other examples of vapor-deposited coatings are aluminum oxide (AlOx) coatings and silicon oxide (SiOx) coatings. Generally, such PVD coatings are more brittle and are not suitable for incorporation into packaging materials by lamination. An exception is metallized layers, which, although formed by PVD, have suitable mechanical properties for lamination materials, but generally offer only a low barrier to oxygen gas.

[0124] Other coatings that have been investigated for laminated packaging materials can be applied by plasma-enhanced chemical vapor deposition (PECVD), in which vapors of compounds are deposited on a substrate in a more or less oxidizing atmosphere. For example, silicon oxide coatings (SiOx) can be applied by PECVD processes, which can provide very good barrier properties under certain coating conditions and gas compositions. Unfortunately, SiOx coatings exhibit poor adhesion properties when laminated to polyolefins and other adjacent polymer layers by melt extrusion lamination, and the laminated materials are exposed to humid or high-humidity packaging conditions. To achieve and maintain sufficient adhesion in packaging laminates of the type intended for liquid carton packaging, specialized and expensive adhesives or adhesive polymers are required.

[0125] According to the present invention, the vapor-deposited coating is an amorphous hydrogenated carbon barrier layer, so-called diamond-like carbon (DLC), applied by a plasma-enhanced chemical vapor deposition process (PECVD). DLC defines a class of amorphous carbon materials that exhibit some of the typical properties of diamond. Hydrocarbon gases, such as acetylene or methane, are used as process gases in the plasma to form the coating. As noted above, such DLC coatings have been found to provide good and sufficient adhesion to adjacent polymer or adhesive layers in laminated packaging materials under humid test conditions. Particularly good adhesive compatibility with adjacent laminated polymer layers, i.e., polymer layers adhered to or coated with the DLC barrier coating, has been observed with polyolefins, particularly polyethylene and polyethylene-based copolymers.

[0126] Therefore, DLC barrier coatings provide good barrier properties and integrity to liquid-filled packages made from packaging laminates that include barrier films or papers bearing this barrier coating, by contributing good mechanical properties and good barrier properties against various substances that migrate through such laminated materials in either the inward or outward direction from the filled package, as well as by resulting in excellent adhesion to adjacent polymer layers in the laminate. Thus, barrier films made from polyester or polyamide substrate layers bearing a DLC barrier coating can provide packaging laminates and packages with oxygen and water vapor barrier properties for extended ambient storage periods, e.g., up to 2-6 months, e.g., up to 12 months. Furthermore, DLC barrier coatings provide good barrier properties against various aromas and flavors present in packaged foods, against small molecules that may be present in adjacent material layers, and against odors and gases other than oxygen. Furthermore, DLC barrier coatings, when coated onto polymer film substrates, exhibit good mechanical properties when laminated to carton-based packaging laminates, and withstand lamination and subsequent folding and sealing of the packaging laminate to filled packages. Polyester and polyamide films provide excellent substrate surfaces for the initiation and growth of DLC coating layers during the vapor deposition coating process. Favorable conditions in the coating process result in improved coating quality, such that thinner coating layers can be formed while achieving desirable barrier, as well as adhesive and cohesive properties.

[0127] The crack-onset strain (COS) of biaxially oriented PET films coated with DLC barrier coatings can be higher than 2%, which generally relates to the oxygen barrier properties of the coating not beginning to degrade until the film is strained beyond 2%.

[0128] DLC coatings have the further advantage of being easily regenerated without residue in the regenerated content, which may contain elements or materials that do not naturally occur in nature and in our surrounding environment.

[0129] The use of adhesive polymers as mentioned above is usually not required for bonding to the DLC barrier coating of the present invention. It has been concluded that a sufficient and suitable adhesion to an adjacent polyolefin layer is at a level of at least 200 N / m, such as at least 300 N / m. Adhesion measurements are performed at room temperature using a 180° peel force tester (Telemetric Instrument AB) 24 hours after LDPE lamination. Peeling occurs at the DLC / LDPE interface, with the peel arm being the barrier film. If necessary, a drop of distilled water is added to the peeled interface during peeling to evaluate adhesion under humid conditions, i.e., when the laminated packaging material is saturated by moisture migration through the material layers from liquids stored in packaging containers made from the laminated material and / or due to storage in a humid or humid environment. The given adhesion value is given in N / m and is the average of six measurements.

[0130] A dry adhesion of greater than 200 N / m ensures that the layers will not delaminate under normal package manufacturing conditions, such as when the laminated material is bent and folded. This same level of wet adhesion ensures that the layers of the laminated packaging will not delaminate after filling and package formation, during transportation, distribution, and storage. The internal bonding polymer layer can be coated directly onto a polymer film substrate onto which a DLC barrier layer has been coated, using common techniques and machinery, such as those for lamination of aluminum foil, particularly high-temperature lamination (extrusion) of the polymer layer from a molten polymer onto the DLC barrier coating. It is also possible to use a prefabricated polymer film and bond this directly to a barrier-coated carrier film by localized melting, for example, by applying heat with a hot cylinder or heated roller. From the above, it is clear that DLC barrier films can be handled in a similar manner to aluminum foil barriers in lamination and conversion to laminated packaging materials, i.e., by extrusion lamination and extrusion coating. Lamination equipment and methods do not require any modification, for example, by adding specific adhesive polymers or binder / tie layers, as may be required with other plasma-coated materials. Furthermore, the novel barrier film, including the DLC barrier layer coated thereon, can be made as thin as aluminum foil without adversely affecting the barrier properties in the final food package.

[0131] When manufacturing the laminated packaging material of the present invention, asymmetric laminate structures having laminated layer structures with unequal elongation stiffness properties on two sides of the spacer layer can result in a problem known as moisture-induced curling, i.e., the flat material does not remain flat when placed on a flat surface, but rather the edges lift and curl toward each other above the plane of the flat portion of the packaging material. An additional benefit of flat laminated side panels in packaging containers is improved grip stiffness, as straight panels are freed from their initial "imperfections," i.e., deflections. Consequently, flat packaging material presents fewer problems when run through a filling machine than curled, distorted packaging material.

[0132] Curling is primarily prevented by matching the facing layers of paper on either side of the spacer layer to have similar elongational stiffness. By doing so, it has surprisingly been found that the compressive strength of the laminate in the x and y directions is also increased. This means that, for example, folded packages made from the folded and laminated packaging material can be stacked on top of each other during distribution and storage at a greater load than liquid food packages currently on the market.

[0133] This allows packages made from such symmetrically sized, laminated packaging materials to have improved package integrity, with the laminated material being less susceptible to damage and cracking of the barrier layer from simple handling and shipping.

[0134] When the mechanical properties of the sandwich material are matched in this way, the various laminated layers, including the barrier layers protecting the packed food from slowly moving oxygen and other gases and steam, also become more resistant to damage and delamination, and as a result, the integrity of the filled and sealed package is also improved in this regard.

[0135] Therefore, a further aspect of improving package integrity is improving the adhesion between the various layers. Particularly good initial adhesion is obtained between dispersion- or solution-coated barrier coatings having hydrophobic functional groups, such as hydroxyl and carboxyl groups, and adjacent layers, such as polyolefins and polyethylene. Also, vapor-deposited, metallized, and DLC-PECVD coatings have been shown to provide very good adhesion properties to adjacent organic polymer layers and films, such that no additional primers or adhesives need to be used between these coatings and adjacent layers in their laminated packaging materials.

[0136] Nevertheless, at least with respect to metallized barrier coating layers, the further enhanced adhesion by lamination of a bonding or adhesive polymer to an adjacent layer has also surprisingly been shown to improve the oxygen barrier properties of the laminated material even further, to a greater degree than could have been imagined.

[0137] Additional oxygen barrier properties can be provided by including a further layer of polymer that acts as a barrier to migrating free fatty acids, such as polyamide in the first pre-laminated material, laminated to the bulk layer. In particular, when a layer comprising a predominantly polyamide portion is added inside the metal barrier layer, this layer can prevent free fatty acids from the packaged food from migrating from the food to the metal barrier, thus maintaining the barrier properties of the barrier layer and maintaining the adhesion of the inner polymer layer to the metal barrier for an extended shelf life.

[0138] The polyamide barrier layer may comprise 50% by weight or more polyamide and the remainder ethylene vinyl alcohol (EVOH) or polyethylene terephthalate (PET) or similar polymers that are compatible with the polyamide and provide barrier properties against the migration of free fatty acids, and may be in the range of 3 to 12 g / m², depending on the requirements of the food product to be packed and the balance of the cost of the materials used. 2, for example, 3 to 8 g / m 2 , for example, 3 to 6 g / m 2 It can be applied in amounts of

[0139] According to a further embodiment, the polyamide barrier layer comprises an aromatic or semi-aromatic polyamide polymer. Such polyamides can provide better barrier properties against migrating free fatty acids, and of course such a combination is particularly advantageous for packaging fruit juices and the like. However, the most common polyamide suitable for the purposes of cost-effective laminated packaging materials and easy manufacturing of such coextrusion coated laminate structures is PA-6.

[0140] Alternatively, the substrate for the barrier coating may be a relatively thin paper having a relatively higher density and Young's modulus than the bulk and spacer layers. Such a barrier substrate paper may be the same paper as the facing paper layer of the sandwich laminated packaging material, or a further such paper of different quality than that used for the facing paper layer.

[0141] Such barrier coating substrate papers that work particularly well can be greaseproof papers or high density papers that have been smoothed and have a pre-coated surface for subsequent barrier coating, particularly vapor-deposited barrier coatings, with the facing layer of such paper, of course, further contributing to the oxygen barrier of the resulting final packaging laminate.

[0142] According to yet a further embodiment, packaging can be obtained that is based on bio-based, possibly renewable materials.

[0143] For example, packaging materials can be produced that have a cellulose-based spacer layer and bulk layer, a paper facing layer that has barrier properties and is further provided with a very thin, nano-thin barrier coating, etc. Furthermore, thermoplastic polymers can be produced from vegetable or organic materials, such as so-called green polyethylene.

[0144] Also, the adhesives or adhesive polymers used in the lamination operation to produce the final laminated packaging material may be entirely bio-based and used in very small amounts, which increases the relative proportion of renewable and cellulose fiber content even further.

[0145] According to a second aspect of the present invention, there is provided a laminated packaging material as produced by the method of the present invention.

[0146] According to a third aspect, there is provided a packaging container from a laminated packaging material produced by the method of the present invention.

[0147] According to a further embodiment of the resulting laminated packaging material, the outermost heat-sealable layer of the laminated material is provided as one or two pre-fabricated films. Thus, such a film may be pre-laminated to the barrier layer of a first pre-laminated material, which is laminated to the first side of the bulk layer, and / or to the printed and decorated outer surface layer, which is laminated to the second side of the bulk layer. When a film is pre-laminated to a barrier layer or a printed and decorated layer, this can be done by simple heat-pressure lamination to the other layers of the film, especially if a pre-coated or integrated layer of adhesive polymer, such as EAA or EMAA, is present on one of the lamination surfaces. Alternatively, it can be done by means of melt extrusion lamination, which is likely more expensive due to the high consumption of intermediate melt extruded polymer, or by pre-coating with a small amount of water-based adhesive that can penetrate onto at least the paper or cellulose-based surface to be laminated without the need for a drying step.

[0148] In the general quest to reduce the cost of laminated packaging materials, it is highly desirable to combine the properties of the various layers so that as few additional layers as possible are required.

[0149] When the traditional liquid packaging paperboard of today's packaging laminates is replaced with a weaker bulk layer, which allows for significant cost savings, some additional costs can be used instead for various custom decorative substrates for printing and decorating the laminated packaging material. Because the bulk layer of the present invention no longer constitutes the printing surface, i.e., the surface to be printed, the expensive clay coat can be omitted from the bulk layer, and a smooth, white printing surface can be obtained by other means on the outer paper-facing printing substrate laminated to the outside of the bulk layer. Such a printing substrate can be, for example, a colored or metallized film, or a facing layer of white printable paper. Alternatively, white paper to provide a white printing background surface can be pre-laminated to a transparent film, which is printed on its reverse side before lamination (i.e., a reverse-printed film), so that the printed decoration is oriented toward the white paper surface and protected by the transparent film substrate. Thus, printing and lamination of the outer white paper facing layer and optionally further lamination of the outermost heat-sealable layer can be done in a previous lamination operation to provide a pre-laminated second material for the second side.

[0150] To further provide low barrier properties and whiteness, such films or papers can be provided with a white filler material, or in the case of paper, with a clay coat and / or, alternatively, a metallized layer. In particular, to minimize production and logistics complexity, the same exterior printed substrate, film, or thin paper may be used for multiple end products, for example, by having one metallized side and another white or colored side. For some product and packaging appearances, a metallized printed surface is preferred, while in other cases a colored printed surface or a brown natural cellulose printed surface is preferred. Separating the printed surface layer from the bulk layer allows for versatility in possible exterior appearances, which is a further advantage of the three-part modular lamination model of this invention. Furthermore, an oxygen barrier layer can be included in a pre-laminated second material to enhance the overall barrier performance of the final laminated material.

[0151] In the following, preferred embodiments of the present invention will be described with reference to the drawings. [Brief explanation of the drawings]

[0152] [Figure 1a] 1A-1C illustrate cross-sectional views of three modular laminate types of laminated packaging materials according to one embodiment of the present application. [Figure 1b] 10A-10C show cross-sectional views of further embodiments of laminated packaging materials of the three modular laminate type. [Figure 1c] 10A-10C show cross-sectional views of yet further embodiments of laminated packaging material of the three modular laminate type. [Figure 1d] 10 shows a cross-sectional view of another further embodiment of a laminated packaging material of the three modular laminate type. FIG. [Figure 2a] 1 illustrates an example of a method for laminating outer (or inner) material modules to a bulk material according to the present invention. [Figure 2b]1A-1C show examples of different methods for laminating inner (or outer) material modules to a bulk material according to the present invention. [Figure 3a] 1 shows a typical example of a packaging container made from a laminated packaging material according to the present invention. [Figure 3b] 1 shows a typical example of a packaging container made from a laminated packaging material according to the present invention. [Figure 3c] 1 shows a typical example of a packaging container made from a laminated packaging material according to the present invention. [Figure 3d] 1 shows a typical example of a packaging container made from a laminated packaging material according to the present invention. [Figure 4] FIG. 1 illustrates the principle of how packaging containers can be produced from packaging laminates in a continuous, roll-fed, form, fill, and seal process. [Figure 5] FIG. 1 illustrates how the curling problem varies with different examples of symmetric and asymmetric laminated layer structures. [Figure 6] FIG. 10 is a diagram showing how compressive strength varies with different laminated material layer configurations, and is at its optimum value when there are symmetrical paper-facing layers positioned on either side of the spacer layer. [Figure 7] 1A-1C illustrate how bending stiffness can be varied by several exemplary sandwich structures within a laminated packaging material. [Figure 8] FIG. 10 shows the resulting reduction in Atsumi after laminating a bulk layer with a spacer layer made of low density foamed cellulose. DETAILED DESCRIPTION OF THE INVENTION

[0153] 1 shows a first embodiment of the laminated packaging material 10a of the present invention in cross section. It is essentially a laminate constructed from three initial modules of material layers that contribute to a sandwich structure, providing a substantially laminated material with its mechanical strength properties and a dimensionally stable final packaging container. Module 1A is a central layer of bulk material consisting of a spacer layer 11a of a low-density cellulose material, such as a foamed fibrous cellulose layer or a layer of fluting material, or any combination of a high-density paper or cellulose-based product with foamed cellulose or fluting material. In this particular embodiment, the material is a 150 g / m 2 A foamed cellulose layer of is used as a spacer layer.

[0154] The outer material module 1B includes a print substrate layer made of thin, high-density paper 12a with a print surface. The paper 12a also forms the outer facing layer of the sandwich structure, adjacent to the spacer layer 11a. In the final laminated material, the substrate 12a is printed and decorated with a print pattern of various colors, images, and text. The outer material module 1B also includes an outermost, liquid-tight, transparent layer 16a made of plastic, preferably a heat-sealable thermoplastic polyolefin such as polyethylene. The print substrate and paper facing layer 12a can be printed before or after lamination to the spacer layer, and the outermost plastic layer 16a is applied to the print substrate layer in a separate operation, either before or after lamination to the spacer layer 11a. If the decorative printing coating with the plastic layer 16a is applied before lamination to the spacer layer of the central module, the entire outer material module is prepared as one module, i.e., a prefabricated outer layer, and then laminated onto the outer side of the central spacer layer to the central module or to the rest of the laminate. The lamination operation can be a melt extrusion lamination operation, with an intermediate thermoplastic bonding layer 14a applied between the spacer layer and the substrate and paper facing layer 12a. However, in this particular embodiment, lamination of the paper facing layer 12a of the printing substrate to the spacer layer 11a of the central module is performed by simply applying a small amount of aqueous adhesive 14a, which is partially absorbed into each cellulose layer and bonds the two paper-cellulose layers together. This adhesive can be starch, nano- / microfiber cellulose, polyvinyl alcohol / polyvinyl acetate, or similar natural substances capable of binding cellulose molecules.

[0155] The inner material module 1C, on the other side of the spacer layer 11a, includes a similar thin, high-density paper facing layer 13a with a barrier coating 18a applied thereto, thus forming a sandwich structure with the spacer layer 11a and the paper facing layer 12a of the outer module. The inner material module also includes an innermost heat-sealable thermoplastic layer 17a, which is also the layer of the packaging laminate that will directly contact the food product in the final package. The innermost heat-sealable polymer layer 17a can be applied by melt extrusion coating or melt coextrusion coating of a multilayer polymer structure onto the inside of the paper facing layer 13a with the applied barrier coating 18a. In this embodiment, the barrier coating is a barrier polymer applied to the paper surface layer by aqueous dispersion coating in the coating and drying operation described above. Alternatively, the barrier polymer can be applied to the thin paper substrate and facing layer by extrusion coating. The barrier-coated paper facing layer could alternatively be oriented in the laminate toward the central module and spacer layer 11a, with the barrier coating 18a facing outward within the packaging laminate, but in this particular embodiment, it is oriented inward toward the innermost sealing layer. In an alternative embodiment, the paper facing layer 13a provides some barrier properties by itself when laminated between polymer layers, such that the coating can be peeled off and still provide some barrier properties, thus being a barrier layer without any additional coating. Examples of such dense papers include certain greaseproof papers with compact surfaces. In addition to their inherent barrier properties, greaseproof papers may be coated with a metallized coating to further enhance the barrier properties. In particular, the metallized layer has the advantage of adding some minor barrier properties to the laminate. The paper facing layer 13a in this example has a thickness of 40 g / m². 2The barrier coated papers 13a-18a are laminated to the spacer layer 11a by a small amount of water-based adhesive 15a that is partially absorbed into at least one of the surfaces that are adhered to each other when the surfaces are pressed together in a press roller nip.

[0156] The facing layer 12a of paper in the outer module can also be such a greaseproof paper, on which the printing surface is disposed, for example by means of a thin clay coat layer or similar white coating layer, in this example 70 g / m 2 It is a high density kraft paper with a white printable surface.

[0157] The (co)extrusion coating of the innermost layer 17a can occur before or after lamination of the inner material module 1C to the central module and spacer layer 11a. The innermost heat-sealable layer or layers 17a can alternatively be applied in the form of a prefabricated film, being a uniaxially or biaxially oriented film, adding some additional stability and durability to a greater extent than that obtained in an extrusion coating operation. Again, the inner material module 1C can be prelaminated as a separate inner module before laminating it to the central module and spacer layer 11c. However, in this particular embodiment, the barrier-coated paper facing layer 13a-18a is first laminated to the spacer layer 11a or to the remainder of the laminated material, i.e., module 1A laminated to outer module 1B, and then the inside of the barrier-coated paper layer is melt-extrusion coated with a layer or layers 17a of heat-sealable polymer, which is a polyolefin that is metallocene-catalyzed linear low-density polyethylene (m-LLDPE) and low-density polyethylene (LDPE).

[0158] The resulting laminate has a bending stiffness well above 340 mN, which is what is typically required for packages belonging to the Tetra Brik Aseptic® 1000 ml family.

[0159] FIG. 1b shows a similar cross-sectional view of a second embodiment of a laminated packaging material 10b. It, too, is essentially a laminate composed of three original modules of material layers that contribute to a sandwich structure, essentially providing the laminated material with its mechanical strength properties and providing a dimensionally stable final packaging container. Module 2A has a central layer of bulk material with a spacer layer 11b of cellulose material, but also has paper facing layers 12b and 13b made of thin, high-density paper and integrated into the central bulk layer in contact with spacer layer 11b. Paper facing layers 12b and 13b can be pre-laminated to spacer layer 11b by a spacer layer material supply device or at a location intended for this purpose. Lamination of the paper facing layer to the spacer layer is accomplished by applying a small amount of aqueous adhesive solution to one of the surfaces to be laminated together; the aqueous adhesive composition is partially absorbed into each cellulose layer, effectively bonding the two paper-cellulose layers together. The adhesive is preferably starch or nano- / microfiber cellulose or polyvinyl alcohol / polyvinyl acetate or similar natural substances, capable of binding cellulose molecules together.

[0160] The outer material module 2B includes a printing substrate layer consisting of a white, prefabricated polymer film 19b with a printing surface. Alternatively, the printing substrate film can have a different color or metallized surface intended for printing with the appearance of a non-white background. In the final laminated material, the substrate 19b is printed and decorated with a printing pattern consisting of various colors, images, and text. The outer material module 1B also includes an outermost, liquid-tight, transparent layer 16b of plastic, preferably a heat-sealable thermoplastic, such as a polyolefin, e.g., polyethylene. The printing substrate 19b can be printed before or after lamination to the central module 2A, and the outermost plastic layer 16b can be applied to the printed substrate film in a separate operation, either before or after lamination to the central module 2A or the remainder of the laminate, i.e., module 2C, with module 2A. If the coating of the decorative printed film 19b with the plastic outer layer 16b is performed before lamination to the central module 2A, the entire outer material module is prepared as one module, i.e., as a prefabricated outer side. The lamination operation is a melt extrusion lamination operation, whereby a thermoplastic intermediate bonding layer 14b is applied between the bulk material layer and the central module 2A and the printed substrate film 19b. The lamination operation may alternatively be performed by applying a small amount of aqueous adhesive solution, which is partially absorbed into the paper facing layer 12b, i.e., the outer side of the central module 2A, effectively bonding the facing layer to the printed substrate polymer film 19b.

[0161] On the other side of the central module 2A, the inner inner material module 2C includes a barrier film 18b, which is a polymer substrate film with a barrier coating applied to one side. The inner material module also includes an innermost heat-sealable thermoplastic layer 17b, which is also the layer of the packaging laminate that will come into direct contact with the food product in the final package. The innermost heat-sealable polymer layer 17b can be a multi-layer polymer structure applied to the inside of the barrier film 18b by melt extrusion coating or melt coextrusion coating. In this embodiment, the barrier coating is a vapor-deposited barrier coating applied to the polymer film substrate by a base layer deposition coating in the vapor deposition operation described above. In this embodiment, the barrier coating is a metallized coating applied by physical vapor deposition, but this is not shown in the figure. The barrier-coated film can alternatively be oriented in the laminate toward the central module and paper facing layer 13b, with the barrier coating facing outward in the packaging laminate toward the central module and paper facing layer 13b, but in this particular embodiment, it is oriented inward toward the innermost sealing layer. The (co)extrusion coating of the innermost layer 17b can occur before or after lamination of the inner material module 2C to the central module 2A. The barrier-coated film 18b is laminated to the spacer layer 11b with a small amount of aqueous adhesive component 15b, which is partially absorbed into at least one of the surfaces to be adhered to each other when the surfaces are pressed together in the press roller nip, without forced drying.

[0162] The innermost heat-sealable layer or layers 17b can alternatively be applied in the form of a prefabricated film, adding some additional stability and durability by being oriented to a greater degree than that achieved in an extrusion coating operation. Again, the inner material module 2C can be prelaminated as a separate module inside, prior to lamination to the central module 2A. However, in this particular embodiment, the barrier-coated film 18b is first laminated to the bulk material or to the remainder of the laminated material, i.e., module 2A laminated to the outer modules 2B, and then the inside of the barrier-coated film is melt-extrusion coated with a layer or layers 17b of heat-sealable polymer, the low-density component of which is a polyolefin comprising a blend of metallocene-catalyzed linear low-density polyethylene (m-LLDPE) and low-density polyethylene (LDPE).

[0163] FIG. 1c shows a cross-sectional view of a third embodiment of a laminated packaging material 10c. It is also essentially a laminate composed of three original modules of material layers that contribute to a sandwich structure, substantially providing the laminated material with its mechanical strength properties and providing a dimensionally stable final packaging container. Module 3A has a central bulk material layer with a spacer layer 11c made of a low-density cellulose material, but also has one paper facing layer 13c made of thin, high-density paper and integrated into the central bulk layer on the inside for contact with the spacer layer 11c. The paper facing layer 13c can be pre-laminated to the spacer layer 11c by a spacer layer material supply device or at a location intended for this purpose. Lamination of the paper facing layer to the spacer layer is performed by applying a small amount of aqueous adhesive solution to one of the surfaces to be laminated together; the aqueous adhesive composition is partially absorbed into each cellulose layer, effectively bonding the two paper-cellulose layers together. The adhesive is preferably starch or nano- / microfiber cellulose or polyvinyl alcohol / polyvinyl acetate or similar natural substances, capable of binding cellulose molecules together.

[0164] The outer material module 3B comprises a printed substrate layer made of high-density paper 12c, which is thin and has a printed surface. The paper 12c also forms the outer facing layer of the sandwich structure, in contact with the spacer layer 11c. In the final laminated material, the substrate 12c is printed and decorated with a printing pattern of various colors, images, and text. The outer material module 3B also includes an outermost, liquid-tight, transparent layer 16c of plastic, preferably a heat-sealable thermoplastic, such as a polyolefin such as polyethylene. The printing substrate and paper facing layer 12c can be printed before or after lamination to the spacer layer, and the outermost plastic layer 16c is applied to the printing substrate layer in a separate operation, either before or after lamination to the spacer layer 11c. If the decorative printing coating with plastic layer 16c is applied before lamination of the central module to the spacer layer, the entire outer material module is prepared as a single module, i.e., a prefabricated outer side, and then laminated to the central module or the rest of the laminate on the outer side of the central spacer layer. The lamination operation can be a melt-extrusion lamination operation, whereby a thermoplastic intermediate bonding layer 14c is applied between the spacer layer and the substrate and paper facing layer 12c. However, in this particular embodiment, lamination of the paper facing layer 12c of the printing substrate to the spacer layer 11c of the central module is performed by applying a small amount of an aqueous solution of adhesive 14a, which is partially absorbed into each cellulose layer and bonds the two paper-cellulose layers together, the adhesive being starch or nano- / microfiber cellulose or polyvinyl alcohol / polyvinyl acetate or similar natural biodegradable material capable of binding cellulose molecules.

[0165] The inner material module 3C, located on the other side of the central module 3A, includes a barrier film 18c, which is a polymer substrate film 18c1 with a barrier coating 18c2 applied to one side. The inner material module also includes an innermost heat-sealable thermoplastic layer 17c, which is also the layer of the packaging laminate that will directly contact the food product filled in the final package. The innermost heat-sealable polymer layer 17c can be applied to the barrier film by melt extrusion or melt coextrusion coating a multilayer polymer structure onto the inside of the barrier film 18c. In this embodiment, the barrier coating is a vapor-deposited barrier coating 18c2 applied onto the polymer film substrate by vapor deposition coating in the aforementioned vapor deposition process. In this embodiment, the barrier coating is diamond-like carbon (DLC) applied by plasma-enhanced chemical vapor deposition (PECVD), which provides the barrier film with, among other things, oxygen and water vapor barrier properties. Alternatively, the base deposition coating can be a metallized coating applied by physical vapor deposition. In this particular embodiment, the barrier-coated side of the barrier film is oriented inward, toward the innermost sealing layer. The (co)extrusion coating of the innermost layer 17c can occur before or after lamination of the inner material module 3C to the central module 3A. The innermost heat-sealable layer or multilayer 17c can alternatively be applied in the form of a prefabricated film, and by being a uniaxially or biaxially oriented film, adds some additional stability and durability to a greater extent than that obtained in an extrusion coating operation. Again, the inner material module 3C can be prelaminated as a separate inner module before laminating it to the central module 3A.However, in this particular embodiment, the barrier-coated film 18c is first laminated to the bulk material or to the remainder of the laminated material, i.e., module 3A laminated to outer module 3B, and then melt-extrusion coated on the inside of the barrier-coated film with a layer or layers 17c of heat-sealable polymer, which is a polyolefin with a low-density composition comprising a blend of metallocene-catalyzed linear low-density polyethylene (m-LLDPE) and low-density polyethylene (LDPE). The barrier-coated film 18c is then laminated to the spacer layer 11c by melt-extrusion lamination with an intermediate thermoplastic bonding polymer comprised of polyethylene 15c.

[0166] FIG. 1d shows a cross-sectional view of a fourth embodiment of a laminated packaging material 10d. It is also essentially a laminate composed of three original modules of material layers that contribute to a sandwich structure that substantially provides the laminated material with its mechanical strength properties and provides a dimensionally stable final packaging container. Module 4A has a central layer of bulk material with a spacer layer 11d of low-density cellulose material, but also has one paper facing layer 13d made of thin, high-density paper and integrated into the central bulk layer on the inside to contact the spacer layer 11d. The paper facing layer 13d can be pre-laminated to the spacer layer 11d by a spacer layer material supply device or at a location intended for this purpose.

[0167] The outer material module 4B includes a printed substrate layer 16d made of thin, high-density paper 12d with a printed surface. The paper 12d also forms the outer, facing layer of the sandwich structure, adjacent to the spacer layer 11d. In the final laminated material, the substrate 12d is printed and decorated with a printing pattern of various colors, images, and text. The outer material module 4B also includes an outermost, liquid-tight, transparent layer 16d made of plastic, preferably a heat-sealable thermoplastic, such as a polyolefin, e.g., polyethylene. The printing substrate and paper facing layer 12d can be printed before or after lamination to the central spacer layer, and the outermost plastic layer 16d is applied to the printing substrate layer in a separate operation, either before or after lamination to the spacer layer 11d. If the decorative printing coating with plastic layer 16d is applied before lamination of the central module to the spacer layer, the entire outer material module is thus prepared as one module, i.e., as a prefabricated outer side, and then laminated to the central module or to the rest of the laminate on the outer side of the central spacer layer. The lamination operation can be a melt extrusion lamination operation, whereby a thermoplastic intermediate bonding layer 14d is applied between the spacer layer and the substrate and paper facing layer 12d. However, in this particular embodiment, lamination of the paper facing layer 12d of the printing substrate to the spacer layer 11d of the central module is performed by applying a small amount of an aqueous solution of adhesive, which is partially absorbed into each cellulose layer and bonds the two paper-cellulose layers together, and this adhesive can be starch or nano- / microfiber cellulose or polyvinyl alcohol / polyvinyl acetate or similar natural biodegradable substances capable of binding cellulose molecules.

[0168] The inner material module 4C, located on the other side of the central module 4A, includes a barrier film 18d, which is a polymer substrate film 18d1 with a barrier coating 18d2 applied to one side. The inner material module also includes an innermost heat-sealable thermoplastic layer 17d, which is also the layer of the packaging laminate that will directly contact the food product filled in the final package. The innermost heat-sealable polymer layer 17d can be applied to the barrier film by melt extrusion or melt coextrusion coating a multilayer polymer structure onto the inside of the barrier film 18d. In this embodiment, the barrier coating is a vapor-deposited barrier coating 18d2 applied onto the polymer film substrate by vapor deposition coating in the aforementioned vapor deposition process. In this embodiment, the barrier coating is diamond-like carbon (DLC) applied by plasma-enhanced chemical vapor deposition (PECVD), which provides the barrier film with, among other things, oxygen and water vapor barrier properties. Alternatively, the base deposition coating can be a metallized coating applied by physical vapor deposition. According to this embodiment, the barrier-coated film is oriented in the laminate so that the barrier coating faces the outside of the packaging laminate, toward the central module and paper facing layer 13d. The (co)extrusion coating of the innermost layer 17d can occur before or after lamination of the inner material module 4C to the central module 4A. The innermost heat-sealable layer or layers 17d can alternatively be applied in the form of a prefabricated film, and by being a uniaxially or biaxially oriented film, it adds some additional stability and durability to a greater extent than that obtained in an extrusion coating operation. Again, the inner material module 4C can be prelaminated as a separate inner module before laminating it to the central module 4A.However, in this particular embodiment, the barrier coated film 18d is first laminated to the bulk material or to the remainder of the laminated material, i.e., module 4A laminated to outer module 4B, and then the inside of the barrier coated film is melt extrusion coated with a layer or layers 17d of heat sealable polymer, which is a polyolefin that is a low density composition comprising a blend of metallocene catalyzed linear low density polyethylene (m-LLDPE) and low density polyethylene (LDPE).

[0169] The barrier-coated film 18d is laminated to the spacer layer 11d by a small amount of water-based adhesive component 15d, which is partially absorbed into at least one of the surfaces to be adhered to each other when the surfaces are pressed together in a press roller nip without forced drying.

[0170] In laminated packaging materials, the facing layer of thin, high-density paper of the outer material module is thus 20 to 100 g / m 2 , for example 30 to 80 g / m 2 , for example 30 to 60 g / m 2 and a density of 600 to 1500 kg / m³. In particular, the facing layer of the paper may be a greaseproof paper coated with a barrier coating, such as a metallized coating, alone or in combination. Some greaseproof papers, when laminated between plastic layers, such as polyethylene laminate layers, have a viscosity of 2 cc / m³. 2 Provides a gas barrier of less than 50%RH and atmospheric pressure at 23°C / day.

[0171] Figure 2a shows diagrammatically how one module can be laminated to another module by low temperature (ambient), i.e., without heat drying or curing, absorption lamination of the aqueous adhesive, by applying a very small amount of aqueous adhesive solution onto one of the surfaces to be laminated to each other, and then the aqueous adhesive is absorbed into one or both of the two surfaces. In the embodiment for producing a laminated packaging material in Figures 1a-1d, the aqueous adhesive solution is applied in adhesive application operation 21 to the surfaces to be laminated of outer material modules 1B; 2B; 3B; 4B, i.e., the non-printed surfaces of printed substrate layers 12a, 12b, 12c, 12d. In the lamination nip between the two nip rollers, the webs of central module material 1A, 2A, 3A, 4A are laminated to the webs of outer module material 1B, 2B, 3B, 4B with a pressure high enough to bond the two surfaces together, but not so high that the low-density spacer layers of the sandwich structure break down, with the two webs simultaneously passing through the lamination nip. The resulting webs of intermediate pre-laminate of two modules 1A+1B, 2A+2B, 3A+3B, 4A+4B are sent to a further lamination station for lamination to a third module or part thereof, as described below in FIG. 2b, or alternatively wound onto reels for intermediate storage or transport to a different time or location where final lamination and finishing steps will occur. A cold aqueous adhesive absorption lamination method can also or alternatively be applied when laminating the inner side of the inner module material to the central module material.

[0172] 2b shows diagrammatically how one module can be laminated to another module by melt extrusion lamination, with the two laminated surfaces bonded to each other by a thermoplastic intermediate bonding layer. According to this example, the prelaminate webs of the two modules laminated in the example of FIG. 2 are fed into the lamination nip simultaneously with the webs of the inner material modules 1C, 2C, 3C, and 4C. At the same time, a molten curtain of thermoplastic bonding polymer 23, 15a, 15b, 15c, and 15d is extruded downward into the lamination roller nip and cooled while pressing the two webs together to achieve sufficient adhesion between the cellulose-based central module, i.e., to the surfaces of the spacer layer 11a or the integrated facing layer 13b, 13c, and 13d and the barrier layer 13a, 18b, or the barrier film 18c and 18d of the inner material module.

[0173] FIG. 3a shows one embodiment of a packaging container 30a made from a packaging laminate 10a, 10b, 10c, or 10d according to the present invention. The packaging container is particularly suitable for beverages, such as sauces, soups, or the like. Typically, such packages have a volume of approximately 100 to 1000 ml. The packaging container 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 such a "wedge shape," only the bottom of the package is folded and molded so that the transverse heat seals at the bottom are hidden under triangular corner flaps, which are then folded and sealed to the bottom of the package. The transverse seals at the top section are left unfolded. In this way, the half-folded package is easy to handle and dimensionally stable when placed on a grocery store shelf, a table, or the like.

[0174] 3b shows an alternative preferred example of a packaging container 30b made from an alternative packaging laminate according to the present invention. This alternative packaging laminate is thinner by having a thinner cellulose bulk layer 11 and therefore is not dimensionally stable enough to form a rectangular, parallelepiped, or wedge-shaped package and cannot be folded and formed after transverse seal 32b. Therefore, the package remains a pillow-shaped pouch-like container and is distributed and sold in this form.

[0175] 3c shows a gable-top package 30c folded from a pre-cut sheet or blank made from a laminated packaging material comprising a bulk layer of paperboard and a durable barrier film of the present invention. Flat-top packages can also be formed from similar blanks of material.

[0176] 3d shows a bottle-shaped package 30d, which combines a sleeve 34 formed from a pre-cut blank of the laminated packaging material of the present invention with a top 35 formed from injection-molded plastic in combination with a screw cork or other opening device. This type of package is sold, for example, under the trademarks Tetra Top® and Tetra Evero®. These particular packages are formed by attaching a molded top 35 with an opening device attached in a closed position to a tubular sleeve 34 of laminated packaging material, sterilizing the bottle-top capsule thus formed, filling it with a food product, and finally folding and forming the bottom of the package to seal it.

[0177] 4 illustrates the principle described in the introduction to this application, where a web of packaging material is formed into a tube 41 by joining its longitudinal edges 42 together at overlapping joints 43. The tube is filled (44) with the intended liquid food product and divided into individual packages by repeated transverse seals 45 of the tube at predetermined distances from each other below the level of the filled contents in the tube. Packages 46 are separated by cutting at the transverse seals and given the desired geometric configuration by folding and shaping the material along prepared creases.

[0178] Figure 5 shows the importance of having symmetry about the spacer layer to obtain sufficient compressive strength of packaging containers made from laminated materials so that the packages can be stacked on top of each other on pallets during storage and distribution without the corners flattening and the packages breaking or twisting from their original rectangular shape, a so-called "buckling". In compression tests of packaging materials, a 70 g / m2 foam layer on either side of a 600 μm thick layer of foamed cellulose 2 It was shown that by using a thin paper facing layer of 70 g / m, the compressive strength of the packaging material was improved by an additional 10% compared to today's existing, high stiffness paperboard-aluminum foil packaging laminates, while an asymmetric structure with aluminum foil on the inside of the spacer layer and a thin paper facing layer on the outside had a significantly reduced package compressive strength. 2 Between the facing layer of paper and the 6.3 μm aluminum foil, different spacer layers were used, consisting of foamed cellulose of different standard fiber type "150ST" and different thicknesses (400, 600, 900 μm). The reference used was an existing 270 mN liquid paperboard as a bulk layer laminated to the same aluminum foil, but only with a polymer layer laminated on the outside of the bulk layer.

[0179] The compressive strength of the packaging material was measured according to Scan-P4683.

[0180] Figure 6 illustrates the importance of symmetry around the spacer layer to prevent laminated packaging materials from exhibiting curling when the relative humidity in the material increases from 50% RH to 90% RH, such as during long-term storage in some environments for liquid-filled packages. The figure thus shows the increase or decrease in curling as humidity increases. Curling at high relative humidity for laminated packaging materials based on bulk layers of paper or paperboard is believed to contribute significantly to the loss of dimensional stability in packaging containers made from the material, such as the phenomenon of bulging folded corners and edges in laminated carton materials. Among asymmetric laminate structures, sandwich structures with a thin paper facing layer on one side and a relatively stiff but very thin aluminum foil or polymer film on the other side have been found to be nearly impossible to prevent from curling the laminated material. Furthermore, a reference material (Sample 4131) with a barrier layer consisting of existing paperboard and aluminum foil exhibited significant curling across the width of the laminate in a humid environment. On the other hand, when the bulk layer is laminated in accordance with the present invention with thin paper on both sides, the problem of increased curling as humidity increases is virtually eliminated, and is not significant even in the machine direction. It is believed to be best that the main facing layers on both sides of the low-density spacer layer are cellulose or paperboard layers that are hygroscopic and absorb the same or at least a similar amount of humidity as the relative humidity (RH) increases in the laminated packaging material. Samples 4180 and 4182 have facing layers of 70 g / m2 high-density paper on both sides of the spacer layer.

[0181] Therefore, having two opposing facing materials that expand in the same way when exposed to increasing relative humidity RH provides a robust packaging material and a package that is not sensitive to weather changes during storage and transport.

[0182] Variants of sandwich packaging material were evaluated for humidity curl by first conditioning the variants at 50, 70, and 90% RH for at least 48 hours. The test was performed using a vernier caliper and a metal plate. The metal plate was placed 10 cm from the edge (in either the CD or MD) of the specimen, and the height between the table and the specimen edge was measured. A - symbol indicates curl toward the inside / foil, otherwise curl toward the outside / decoration.

[0183] FIG. 7 similarly shows how the bending stiffness of a laminated packaging material is increased by the incorporation of at least one paper facing layer on the side of a low stiffness bulk paperboard or low density cellulose-based spacer layer.

[0184] The laminated samples tested for bending stiffness were 1: 80mN stiffness cardboard for small packages 2: 1 paperboard laminated with 6.3 μm thick aluminum foil 3:40g / m 2 1 sheet of paperboard laminated with 1 sheet of greaseproof paper 4:72g / m 2 A bulk layer consisting of 165 g / m² fluting material laminated to a 6.3 μm thick aluminum foil on one side. 5:72g / m 2 Paper laminated on one side, 40g / m 2 165g / m greaseproof paper laminated on the other side 2 A bulk layer consisting of fluting material is.

[0185] Figure 8 shows the resulting thickness reduction after laminating the bulk with a spacer layer made of foamed cellulose. For example, the identification (ID) "FC 300 2x" indicates a density of 300 kg / m 3This means that the foamed cellulose is laminated at twice the nip load of the reference. In general, it can be seen that the residual thickness of the foamed cellulose is substantially greater than that of laminated versions with foamed polymer materials at similar lighter loads.

[0186] In addition, lamination by extrusion coating is 300 kg / m 3 It was concluded that this method works well for cellulosic foams having a density of 100 MPa. Typically, bulk or spacer layers having lower density materials are more sensitive to the heat and pressure of lamination, but exhibit a greater reduction in foam thickness.

[0187] Furthermore, although the thickness reduction of the polymer foam is permanent, there is a springback effect in the cellulose foam spacer layer due to the melting and reformation of the cells of the heated polymer foam, which results in a thickness reduction of approximately 300-400 kg / m during lamination. 3 At densities of 10 to 15 percent, the foam recovers to its final thickness, which is reduced by only about 10 to 15 percent at the reference nip. The higher the density of the cellulose foam, the greater this springback effect, or compressive force in the z-direction (ZD). Therefore, it was concluded that, unlike other lightweight materials, cellulose foam works for lamination into laminated packaging materials with sufficient bending stiffness and mechanical stability to form dimensionally stable, fold-formed packages for packaging liquid foods, despite the very low density of such spacer materials.

[0188] Thus, it can be seen that a bulk layer with a low bending stiffness can be better supported on at least one side by a facing layer of paper, and it is clearly best to have such a facing layer of paper on both sides of the bulk layer. The bending stiffness of the samples was measured by Lorentzen & Wettre according to ISO 2493-1.

[0189] Thus, we have found that the new laminated packaging material of the present invention also makes it possible to provide a packaging container for liquid or wet foods that has good integrity properties even under wet conditions, i.e., has a long shelf life.

[0190] Generally, the basis weights stated above and below were measured by SCAN P 6:75. The density and thickness of the materials were measured by ISO 53:1988.

[0191] The present invention is not limited to the embodiments shown and described above, but may vary within the scope of the claims. As a general note, the ratios between layer thicknesses, the distances between layers, and the sizes of other features compared to each other and their relative sizes should not be taken as shown in the figures, which merely illustrate the order and type of layers for each of all other features that are understood to be described in the text of this specification. [Explanation of symbols]

[0192] 1A;2A;3A;4A Central Module 1B;2B;3B;4B Outer material 1C;2C;3C;4C Inner Material Module 10a;10b;10c;10d Packaging material 11a;11b;11c;11d spacer layer 12a; 12c; 12d Printing substrate layer, paper facing layer 12b;13c;13d Paper facing layers 13a;18b;18c;18d Barrier layer 16a;16b;16c;16d Protective layer 17a;17b;17c;17d Heat sealable layer 18b;18c;18d Barrier Coating 19b Printing base material layer 21d Decoration 30a;30b;30c;30d Packaging container

Claims

1. 1. A method for producing a laminated, foil-free, cellulose-based packaging material (10a; 10b; 10c; 10d) for liquid or semi-liquid food products for heat sealing into packages having sufficient mechanical strength and barrier properties and an attractive appearance, comprising: a) providing a web of central modules (1A; 2A; 3A; 4A) of bulk material comprising spacer layers (11a; 11b; 11c; 11d) of cellulose, said spacer layers being linerboard material or containerboard including fluting material, having a Short Compression Test Index (SCT Index) value in the machine direction (MD) of at least 30 Nm / g in, determined in accordance with ISO 9895 and ISO 536, and a compressive strength of at least 850 kg / m ３ Lower density and 60 to 250 g / m ２ and having a bending stiffness, when excluding the basis weight of the printable coating (clay coat), that is 30 to 100% less than the bending stiffness of the liquid carton paperboard at the corresponding basis weight; b) providing a web of outer material modules (1B; 2B; 3B; 4B) comprising at least one printed substrate layer (12a; 12b; 12c; 12d) with or without a printed or applied decoration (21d) thereon, said outer material modules being intended for the bulk material side of said central module, which is oriented towards the outside of a packaging container made of said laminated packaging material, c) laminating the outer sides of the web of bulk material of the central module and the webs of the outer material modules to each other; d) adding said decoration (21d) to said outer material module; e) providing a web of inner material modules (1C; 2C; 3C; 4C), said inner material modules comprising a polymer film with a barrier coating (18b; 18c; 18d), said polymer film being laminated to the inner surface of said bulk material by means of an intermediate bonding layer or adhesive, said inner material modules being intended for the side of said bulk material that is oriented towards the inside of a packaging container made of said laminated packaging material, f) laminating the webs of the inner material modules and the inner side of the web of bulk material of the central module to each other; g) applying an outermost transparent and liquid-tight protective layer (16a; 16b; 16c; 16d) to the outside of the outer material module; h) applying an outermost thermoplastic, liquid-tight and heat-sealable layer (17a; 17b; 17c; 17d) to the inside of the inner material module; i) obtaining a web of said laminated cellulose-based packaging material for liquid or viscous foods; Equipped with 12. A method according to claim 11, wherein the spacer layer (11a; 11b; 11c; 11d) constitutes the centre of a sandwich structure within the laminated packaging material, the sandwich structure having at least one paper facing layer (12a; 12b; 12c; 12d) arranged on at least one side of the spacer layer and in contact with a further facing layer arranged on the other side of the spacer layer, the paper facing layer and the further facing layer having a thickness and a higher Young's modulus than the spacer layer.

2. 2. The method of claim 1, wherein the bulk material comprises a spacer layer (11a) and the inner and outer material modules each comprise a facing layer (12a, 12b) of paper.

3. 2. The method of claim 1, wherein the bulk material comprises a spacer layer (11c; 11d) and an integrated paper facing layer (13c; 13d) directly adjacent the inner side of the spacer layer, while the outer material module comprises a further paper facing layer (12c; 12d).

4. 2. The method of claim 1, wherein the bulk material comprises a spacer layer and a facing layer of paper immediately adjacent the outer side of the spacer layer, while the inner material module comprises a further facing layer of paper.

5. The facing layer of the paper has a density of 20 to 100 g / m ２ Basis weight: 600 to 1500 kg / m ３ 5. The method according to claim 1, wherein the porous material has a density of 0.1 to 1.0 GPa and a Young's modulus of 1 to 10 GPa.

6. The density of the spacer layer is 750 kg / m ３ 6. The method according to claim 1, wherein the axial length of the slit is less than 100 mm.

7. 7. The method according to any one of claims 1 to 6, characterized in that the outer material module (1B; 3B; 4B) comprises a facing layer (12a; 12c; 12d) of paper having a printable or printed surface oriented towards the outside of the module, laminated to the outer surface of the bulk material by means of an intermediate bonding layer or adhesive.

8. 8. The method according to any one of claims 1 to 7, wherein the printable surface is a clay-coated white paper surface, or a metallized film, or a metallized paper surface.

9. The outer material module has a thickness of 0.5 to 4 g / m on one of the surfaces that are laminated to each other. ２ 9. The method according to claim 1, wherein the aqueous adhesive composition is applied to the bulk material in an amount of 0.1 to 10 ...

10. The inner material module has a thickness of 0.5 to 4 g / m on one of the surfaces to be laminated together. ２ 10. The method according to claim 1, wherein the aqueous adhesive composition is applied to the bulk material in an amount of 0.1 to 1.0 ...

11. A laminated packaging material obtained by the method according to any one of claims 1 to 10.

12. A packaging container (30a; 30b; 30c; 30d) comprising the laminated packaging material of claim 11.

Images