Barrier-coated cellulosic substrate, laminate packaging material, and packaging container comprising a cellulosic base material

Abstract

The present invention relates to a high-quality heat-sealable gas-barrier-coated cellulosic substrate (10). The present invention further relates to a laminated packaging material (20) comprising a barrier-coated cellulosic substrate (10; 25) suitable for heat-sealable packaging of oxygen-sensitive products and to a packaging container manufactured from this laminated packaging material.

Description

Technical Field

[0001] The present invention relates to a barrier-coated cellulose-based substrate for packaging oxygen-sensitive products such as foods. The present invention further relates to a method for producing a barrier-coated cellulose-based substrate, a laminated packaging material including a barrier-coated cellulose-based substrate for packaging oxygen-sensitive products such as liquid or semi-liquid foods, and a packaging container including the laminated packaging material.

Background Art

[0002] Disposable type packaging containers for liquid foods are often manufactured from packaging laminates based on paperboard or carton. One such commonly used packaging container is sold under the trademark "Tetra Brik Aseptic®" and is mainly employed for the aseptic packaging of liquid foods such as milk and fruit juice sold for long-term storage at room temperature. The packaging material of this known packaging container is usually a laminate including a bulk or core layer of paper, paperboard, or other cellulose-based materials and a liquid-tight outer layer of a thermoplastic plastic. In order to make the packaging container gas-tight, particularly oxygen-tight, for example, for the purpose of aseptic packaging and packaging of milk and fruit juice, the laminate of these packaging containers usually includes at least one additional layer, most commonly an aluminum foil.

[0003] On the inside of the laminate, i.e., the side intended to face the filled food contents of the container manufactured from the laminate, there is an innermost layer coated on the aluminum foil, and this innermost layer includes one or more sub-layers containing a heat-sealable thermoplastic polymer such as an adhesive polymer and / or a polyolefin. Also, outside the bulk layer, there is an outermost heat-sealable polymer layer.

[0004] Packaging containers are generally manufactured by the latest high-speed packaging machines of the type that form, fill, and seal packages from a web of packaging material or a pre-assembled blank. The packaging containers are manufactured by joining the longitudinal edges of a web of laminated packaging material to each other at an overlap joint by welding together the inner and outer heat-sealable thermoplastic polymer layers and reforming them into a tube. The tube is filled with the intended liquid food, and then it is divided into individual packages by repeatedly sealing the tube transversely at a predetermined distance from each other at a position lower than the height of the contents within the tube. The packages are separated from the tube by making a cut along the transverse seal and are formed into the desired geometric shape, usually a parallelepiped, by forming creases along the crease lines pre-prepared in the packaging material. Each package may be equipped with an opening device such as a screw cap before or after the filling, forming, and sealing of the container.

[0005] The main advantage of this concept of a continuous tube-forming, filling, and sealing packaging method is that the web can be continuously sterilized immediately before tube formation, offering the possibility of an aseptic packaging method, i.e., a method in which the liquid contents to be filled and the packaging material itself are reduced from bacteria and the filled packaging containers are manufactured under clean conditions so that they can be stored for a long time even at ambient temperature without the risk of microbial growth in the filled product. Another important advantage of the Tetra Brik® type of packaging method is the possibility of continuous high-speed packaging, which has a major impact on cost efficiency, as described above.

[0006] Sensitive liquid foods, such as milk and juice, can also be packaged in containers made from the sheet blanks or pre-assembled blanks of the laminate packaging material of the present invention. From a flat-folded tubular blank of the packaging laminate, the blank is first assembled to form an open tubular container capsule, and one open end thereof is closed by folding and heat-sealing an integral end panel, thereby producing a package. The container capsule thus closed is filled with food, such as juice, etc., from the other open end, and then closed by further folding and heat-sealing the corresponding integral end panel. An example of a packaging container manufactured from sheet and tubular blanks is the conventional so-called gable-top package. Also, some packages of this type are provided with a molded top and / or a screw cap made of plastic.

[0007] The aluminum foil layer of the packaging laminate provides a very excellent gas barrier property compared to other gas barrier materials. Conventional aluminum foil-based packaging laminates for aseptic packaging of liquid foods also have inherent barrier properties against water vapor, light, aroma, flavor, and acidic substances, and at their performance levels, they are the most cost-effective among the packaging materials currently available on the market. Furthermore, by induction to the aluminum foil, the aluminum foil enables heat-sealing and heating of the laminate material.

[0008] Other materials competing with the foil-based materials need to have good cost efficiency regarding raw materials, have equivalent food preservation characteristics, and relatively low complexity in converting the materials into the finished packaging laminate.

[0009] In the development efforts of non-aluminum foil materials for carton packaging of liquid foods, there is also a general desire to develop pre-manufactured films and sheets with high barrier properties or multi-barrier properties that can replace the aluminum foil barrier material of the conventional laminate packaging material or combine multiple other barrier layers in the laminate material and be adapted to the conventional processes for laminating and manufacturing.

[0010] A preferred type of such alternative, more environmentally sustainable barrier material is a barrier-coated paper substrate made by an aqueous dispersion coating or a vapor deposition coating on a thin paper carrier substrate. There are various aqueous dispersion coating processes, vapor deposition coating processes, and material recipes for such coatings, and there is a need for a cost-effective barrier material of the "non-foil" type, i.e., non-aluminum foil, having barrier properties, particularly improved properties against gases such as oxygen gas, for use in packaging laminates for liquid food packaging.

[0011] International Patent Application Publication WO2011 / 003565A1 discloses a non-aluminum foil packaging material comprising a pre-coated and metallized paper or cellulose-based substrate for induction heat sealing. Also, in order to obtain good gas barrier properties, it is recommended to further provide a barrier coating layer on a packaging laminate, such as the back surface of a paper substrate or a paperboard bulk layer.

[0012] International Patent Application Publication WO2017 / 089508A1 discloses that in a similar packaging laminate, improved barrier properties can be obtained in a similar manner from metallized paper by selecting a paper substrate that provides optimal properties. Such a metallized paper substrate not only provides improved barrier properties but also shows better stability of the metallized layer for induction heat sealing purposes.

[0013] However, there remains a need for a more robust and reliable barrier-coated cellulose-based substrate that provides both optimal oxygen gas barrier properties and highly reliable heat sealability by high-frequency induction heating.

[0014] Also, there generally remains a need for improvement with respect to the recyclability and sustainability of the materials used, aiming to reduce the amount of materials and the number of types of materials used. Summary of the Invention Problems to be Solved by the Invention

[0015] The object of the present invention is to provide a barrier-coated cellulose-based substrate suitable as a gas barrier material in the packaging of oxygen-sensitive products, such as foods, especially liquid or semi-liquid or wet foods. It is also to provide a barrier-coated cellulose-based substrate suitable for future sustainable non-aluminum foil-based ("non-foil") laminate packaging materials used for heat-sealing oxygen-sensitive products into heat-sealable packages by high-frequency induction heat sealing.

[0016] A further object of the present invention is to provide a barrier-coated cellulose-based substrate that has good gas barrier properties and high-frequency induction heat-sealing properties and meets the needs of future sustainable packaging materials for packages of oxygen-sensitive products, i.e., packaging materials with improved recyclability and sustainability.

[0017] A more specific object is to provide barrier-coated paper or cellulose-based substrates suitable for use in non-foil heat-sealable laminate packaging materials and in packaging containers for liquid, semi-liquid or viscous foods, enabling long-term aseptic storage under ambient conditions.

[0018] A further object is to provide a heat-sealable non-foil laminate packaging material based on reliable paper or cardboard that has good gas barrier properties and water vapor barrier properties, is easily recyclable, environmentally sustainable, and is intended for the packaging and wrapping of oxygen-sensitive products such as foods.

[0019] A further specific object of the present invention is to provide a reliable non-foil packaging laminate based on paper or cardboard that has high gas barrier properties and water vapor barrier properties for the purpose of manufacturing aseptic packaging containers for long-term storage of liquid, semi-liquid or viscous foods while maintaining their nutritional quality under ambient conditions.

[0020] According to the present invention, these objects can be achieved by a barrier-coated paper or cellulose-based substrate, a laminate packaging material, and a packaging container as defined in the appended claims.

Means for Solving the Problems

[0021] According to a first aspect of the present invention, there is provided a barrier-coated cellulose-based substrate for use as a barrier sheet of a heat-sealable laminate packaging material for packaging oxygen-sensitive products. The barrier-coated cellulose-based substrate comprises a cellulose-based substrate and a base coating applied to the surface of the first side of the cellulose-based substrate by dispersion coating or solution coating and subsequent drying, thereby providing a smooth and thermomechanically resistant base coating. The base coating contains 60% by weight or more of a material selected from the group consisting of starch, modified starch materials, and cellulose ethers. The barrier-coated cellulose-based substrate further comprises a metallized coating applied onto the free surface of the base coating. The metallized coating is applied onto the base coating by a vapor deposition method. The barrier-coated cellulose-based substrate further comprises a heat-resistant gas barrier top coating. The heat-resistant gas barrier top coating is applied onto the metallized coating by dispersion or solution coating and then dried. The heat-resistant gas barrier top coating is further coated with a heat-sealable layer of a thermoplastic material or laminated to a heat-sealable layer of a thermoplastic material. The heat-resistant gas barrier top coating has a melting temperature higher than that of the heat-sealable layer of the thermoplastic material. The barrier-coated cellulose-based substrate provides good gas barrier properties and enables robust induction heat-sealing conditions in a laminate packaging material for manufacturing packages.

[0022] The base coating may contain 70% by weight or more, for example 80% by weight or more, for example 90% by weight or more, for example 95% by weight or more of a material selected from the group consisting of starch, modified starch materials, and cellulose ethers.

[0023] Preferably, the base coating contains starch or a modified starch material.

[0024] Alternatively or additionally, the base coating may contain a cellulose ether material. The base coating may contain one or more cellulose ethers selected from the group consisting of methyl cellulose, ethyl cellulose, carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), hydroxypropyl methyl cellulose (HPMC), and sodium carboxymethyl cellulose (NaCMC) instead of or in addition to starch or starch-based materials.

[0025] The metallization coating is a vapor deposition coating of a metal such as an aluminum coating.

[0026] The heat-resistant gas barrier top coating may contain a polymer selected from the group consisting of vinyl alcohol polymers and copolymers, and polymers such as polyvinyl alcohol (PVOH) and ethylene vinyl alcohol (EVOH), and a modified (co)polymer such as a polymer blend containing such a polymer in a majority, that is, in a proportion exceeding 50% by weight.

[0027] The base material has a basis weight measured according to ISO 536:2012 of 30 to 70 g / m 2 and a density measured according to ISO 534:2011 of 800 kg / m 3 ~1400 kg / m 3 and may be paper.

[0028] According to a second aspect of the present invention, there is provided a method for manufacturing a barrier-coated cellulose-based substrate for use in packaging oxygen-sensitive products, the method comprising the following steps. a) conveying a continuous web of a cellulose-based substrate; b) providing an aqueous-based coating composition comprising at least 60% by weight of a material selected from the group consisting of starch, modified starch materials and cellulose ethers, based on dry weight; c) applying the aqueous-based coating composition to the upper surface of the web of the cellulose-based substrate by dispersion coating such as roll coating; d) drying the aqueous gas barrier polymer coating applied in step c) to form a smooth base coating layer; e) optionally repeating steps c) and d); f) vapor deposition coating a metallized coating on the base-coated and dried web substrate obtained in step e); g) applying an aqueous solution or dispersion of a heat-resistant gas barrier top coating material, preferably by roll coating, onto the metallized coating; h) drying the aqueous solution or dispersion applied in step g) to obtain a heat-resistant gas barrier top coating; i) optionally repeating steps g) and h); j) obtaining a barrier-coated cellulose-based substrate with defects in the base coating, gas barrier top coating, and metallized coating minimized; k) further coating the surface of the heat-resistant gas barrier top coating with a heat-sealable layer of a thermoplastic material, wherein the heat-resistant gas barrier top coating layer has a higher melting temperature than the heat-sealable layer of the thermoplastic material.

[0029] The heat-resistant gas barrier top coating material may have a polymer selected from the group consisting of vinyl alcohol polymers and copolymers, such as polyvinyl alcohol, PVOH, ethylene vinyl alcohol, EVOH, modified vinyl alcohol polymers and copolymers, such as modified PVOH and modified EVOH, and blends consisting of a majority of such polymers.

[0030] According to a third aspect of the present invention, a laminated packaging material is provided, the laminate packaging material comprising a barrier-coated cellulosic substrate produced by the method of the first aspect, and further comprising a first outermost protective material layer and a second innermost liquid-tight and heat-sealable material layer.

[0031] The first outermost protective material layer may be a thin layer of polymer having the purpose of protecting a laminate packaging material based on paper or cardboard from dirt and moisture in the external environment of a sealed packaging container.

[0032] The second innermost liquid-tight and heat-sealable material layer may comprise a layer of a thermoplastic polymer and is easily heat-sealable by available heat-sealing methods such as induction heat-sealing, ultrasonic heat-sealing, or simply contact heat-sealing.

[0033] The second innermost liquid-tight and heat-sealable material layer may comprise polyethylene from the low density range, such as selected from the group consisting of polyolefin polymers, such as LDPE, LLDPE, m-LLDPE, and any blend of two or more thereof.

[0034] According to one embodiment, both the first outermost protective material layer and the second innermost liquid-tight and heat-sealable material layer may comprise a polyolefin polymer such as the same type or different types of polyethylene polymers.

[0035] For the purpose of carton packaging of oxygen-sensitive products such as liquid, semi-liquid or viscous foods, the laminate packaging material may further include a bulk layer of paper or cardboard or other cellulosic material, and inside the bulk layer of paper or cardboard, a barrier-coated cellulosic substrate disposed between the bulk layer and a second innermost liquid-tight and heat-sealable material layer. The bulk layer contributes to the bending stiffness of the laminate packaging material and can also contribute to the dimensional stability of the folded and formed packaging container made therefrom to withstand strong acting forces caused, for example, by the flow and movement of the packaged contents of liquid or viscous oxygen-sensitive products during distribution and handling. In such a laminate, the metallized coating is preferably directed towards the inside of the packaging container, i.e., while the cellulosic substrate is directed towards the bulk layer, the barrier coating is directed towards the innermost layer.

[0036] In one embodiment, for the purpose of such liquid carton packaging, the second innermost liquid-tight and heat-sealable polyolefin layer is an oriented polyethylene film made of a pre-manufactured polyolefin film, for example, at least one layer having a majority of an LLDPE polymer, etc., to improve the robustness of the mechanical properties of the laminate packaging material.

[0037] In a fourth aspect of the present invention, a packaging container is provided that includes the laminate packaging material of the third aspect. According to an embodiment, the packaging container is at least partially manufactured from the laminate packaging material of the present invention, and according to a further embodiment, the entire packaging container is manufactured from the laminate packaging material of the present invention.

[0038] By using a barrier-coated cellulosic substrate as described above and in the present invention, good gas barrier properties can be provided in the laminate packaging material and the packaging container made therefrom, and by increasing the content of water-repellent cellulosic fibers, improved water repellency and recyclability characteristics, i.e., improved sustainability, can be provided.

[0039] Generally, when a cellulosic substrate is used in a laminate material and a package, the proportion of the fiber content that is renewable, i.e., of non-fossil origin, and can be recycled or biodegraded to recycle old materials into new materials increases. Further, when paper or a cellulosic substrate is used as the "surface layer" in a sandwich configuration, it becomes possible to use a bulk material with low bending rigidity, simplifies the design for maximizing bending rigidity, and / or has a low density and less fiber usage, and the cost is reduced by laminating such surface layers on both sides of the bulk layer.

[0040] Thus, the gas-barrier coated cellulosic substrate of the first aspect provides good oxygen barrier properties and good heat sealability to the laminate packaging material containing it due to the resulting material layer configuration, and can further impart good recyclability and sustainability profile.

[0041] (Detailed Description) The term "long-term storage" as used in connection with the present invention means that the package can store the quality of the food packaged in the packaging container, i.e., nutritional value, hygienic safety, and taste, for at least one or two months, e.g., at least three months, preferably six months, e.g., twelve months, or more at ambient temperature conditions.

[0042] The term "package integrity" generally means the airtightness of the package, i.e., the resistance to leakage and breakage of the packaging container. This term encompasses the resistance of the package to the intrusion of microorganisms such as bacteria and dirt that can deteriorate the filled food and shorten the expected shelf life of the package.

[0043] One of the main contributions to the integrity of the package of the laminate packaging material is brought about by the good internal adhesion between adjacent layers of the laminate material. Another contribution is brought about by the resistance of the material to defects such as pinholes and breaks in each material layer, and still another contribution is brought about by the strength of the seal joint where the material is sealed during the formation of the packaging container. Thus, with regard to the integrity of the laminate packaging material itself, attention is paid to the adhesiveness between each laminate layer and its adjacent layer, and the ability of each material layer to withstand thermal and mechanical loads during folding and sealing, for example, for forming the packaging container. With regard to the seal of the packaging container, the integrity mainly focuses on the quality of the seal joint, which is ensured by a strong sealing operation that functions well in the filling machine, and further, this is ensured by the properly adapted heat-sealing characteristics of the laminate packaging material.

[0044] The term "liquid or semi-liquid or viscous food" generally refers to a food having a fluid content and optionally containing solid food fragments. Dairy products and milk, soy, rice, cereal and seed beverages, juices, nectars, soft drinks, energy drinks, sports drinks, coffee or tea beverages, coconut water, wine, soups, crushed tomatoes, sauces (such as pasta sauce), beans and olive oil, etc. are some non-limiting examples of the foods contemplated.

[0045] Further examples of other oxygen-sensitive foods that can be packaged and protected with the laminate packaging material of the present disclosure are, for example, dried foods and / or fatty foods, etc.

[0046] The term "sterile" related to the packaging material and the packaging container refers to a state in which microorganisms have been removed, inactivated, or killed. Examples of microorganisms include bacteria and spores. Generally, when the product is aseptically filled into the packaging container, an aseptic process is used. In order to maintain the aseptic state during the storage period of the packaging container, the integrity characteristics of the package are very important. For the long-term storage of the filled food, it is also important to have a barrier against gases and vapors such as oxygen gas in order to maintain the original taste and nutritional value, for example, the vitamin C content.

[0047] The term "bulk layer" generally refers to the thickest layer or layer containing the most material in a multi-layer laminate, i.e., the layer that contributes most to the mechanical properties and dimensional stability of the laminate and the packaging container folded from the laminate, such as paperboard or carton, etc. It can also refer to the layer that provides a greater thickness distance in the sandwich structure, which further interacts with stabilizing facing layers having a higher Young's modulus on either side of the bulk layer to achieve sufficient mechanical properties of the formed packaging container.

[0048] The term "non-foil" packaging material refers to laminate packaging materials that do not contain aluminum foil, typically 6-9 μm thick, on the micrometer scale, such as aluminum foil used in conventional liquid carton packaging. However, "non-foil" packaging materials may also contain a metallized layer, for example, because the thickness of the aluminum metallized layer is on the nanometer scale. The amount of aluminum material used in such metallized coatings is very small, significantly reducing the impact on recycling and resource development compared to aluminum foil.

[0049] The term "thermo-mechanical stability" with respect to a material or material layer means that the material has the ability to maintain its mechanical stability and shape at elevated temperatures, and that the metallized layer is well supported and not degraded by such material or layer when the material is molded or formed (pressed, folded, heat sealed, etc.). Furthermore, the material does not melt or soften when heated to a predetermined temperature.

[0050] OTR is measured according to ASTM F1927-14 and ASTM F1307-14 using an Oxtran 2 / 21 (Mocon) instrument based on a coulometric sensor.

[0051] The method for measuring OTR is to determine the surface and the amount of oxygen per unit time when the material passes through it for 24 hours under a defined temperature, a predetermined atmospheric pressure, and a specific time, that is, in an atmosphere of atmospheric pressure 20, or 100% oxygen represented as 0.2 or 1 atm (oxygen). For details of the OTR measurement method, refer to the examples.

[0052] The sheet resistance (Rs) of the metallized coating may be measured by a non-contact method for the laminated material, and a NAGY type SRM-12 instrument manufactured by Nagy Instruments in Germany may be used. The setting range of the measurement related to the present invention is 0.2 to 8 ohms. The measurement was performed on samples with a size of 0.05 × 0.05 meters (5 × 5 cm) for only the laminate packaging material and the metallized material. Nine measurement points were taken from a 1-meter length portion of a web with a width of 0.17 m, that is, three measurement points from the center of the web and three measurement points near each end of the web portion were taken. For a sample with a uniform density, the sheet resistance is the value R given by the basic formula R = density * L / W * t, where L and W are the sides of a square sheet area of the same length, and t is the thickness of the sheet. The unit is measured in ohm / square (Ω□).

[0053] The base materials suitable for the method of the present invention are not limited to a specific type of paper or cellulose, and also include other cellulose-based base materials based on any type of fibrous cellulose. However, the present invention does not apply to base materials made of plastics or polymers such as films made from regenerated cellulose, so-called microfibrillated cellulose or nanofibrillated cellulose (MFC or NFC), or films or papers consisting of 50% by weight or more, or papers having layers or coatings containing 50% by weight or more of MFC or NFC.

[0054] In order to be suitable for the final barrier coating step by the vapor deposition coating process, the cellulose-based base material is thin, and the basis weight measured according to ISO 536:2012 is 30 to 70 g / m 2 , for example, 30 to 60 g / m 2, for example, 35 to 50 g / m 2 , for example, 35 to 45 g / m 2 and having a density of 800 kg / m 3 ~1400 kg / m 3 , for example, 900 to 1400 kg / m 3 , for example, 950 to 1400 kg / m 3 is required. For reasons of efficiency and production economy, and also to avoid coating swelling due to air or moisture trapped in the fibrous and porous cellulose-based substrate during the coating and drying operations, a cellulose-based substrate with a high density, relatively light weight and thickness may be required. On the other hand, a cellulose-based substrate with a basis weight of less than 30 g / m 2 may have mechanical weakness or low dimensional stability and shrinkage or curling problems when coated with a wet dispersion and dried.

[0055] Therefore, it is more preferable to use a cellulose-based substrate having a basis weight of 30 to 50 g / m 2 , most preferably 35 to 45 g / m 2 and a density of 900 kg / m 3 ~1400 kg / m 3 .

[0056] The thickness of the cellulose-based substrate can be 35 to 65 μm, for example 35 to 60 μm, for example 35 to 50 μm, for example 35 to 45 μm. In some applications, such as the liquid-tight packaging of wet or liquid or viscous products, it has been found advantageous to use the thinnest possible high-density paper substrate, because less polymer may be required for the adjacent liquid-tight or heat-sealable layer while maintaining the integrity of the package and its heat seal.

[0057] The paper or cellulosic substrate suitable for the present invention has a roughness of the surface to be coated (upper surface or printing surface) of less than 200 ml / min Bendtsen, for example, 180 ml / min Bendtsen or less, for example, 150 ml / min Bendtsen or less, for example, 130 ml / min Bendtsen or less, for example, 120 ml / min or less, for example, 100 ml / min or less, for example, 80 ml / min or less, for example, 50 ml / min or less, for example, 30 ml / min or less, for example, 25 ml / min or less, as measured according to ISO 8791:4.

[0058] If the surface roughness measured as the Bendtsen value (ml / min) is too high, there may be "valleys" and "mountains" on the surface of the cellulosic material. Even if a thin wet coating of an aqueous solution of the gas barrier polymer is applied, it is impossible to fill the "valleys" to make it flat and also impossible to cover the "mountains". In such a case, the coating of the applied and dried gas barrier polymer does not completely cover the surface and has defects, from which oxygen gas molecules can easily permeate through the coating. Therefore, the contribution of the gas barrier properties by such a defective and insufficient barrier coating is significantly reduced. The rougher the surface of the substrate, of course, the more polymer coating needs to be applied, but this is possible even by reducing the coating line speed. However, when the coating speed is high, there are limits to the amount of aqueous coating that can be applied, the amount of water that can evaporate during the drying operation, and the viscosity and solid content of the aqueous barrier polymer solution.

[0059] In one embodiment, for good functioning in barrier coating in industrially feasible high-speed operations, a surface roughness of less than 200 ml / min Bendtsen, for example, less than 120 ml / min Bendtsen, for example, less than 100 ml / min, for example, less than 80 ml / min, for example, less than 50 ml / min, for example, less than 30 ml / min, for example, less than 25 ml / min is preferred. At less than 30 ml / min, the substrate surface is actually smooth, and 0.5 g / m of the thermally stable polymer or composition 2A very thin coating can be applied at high speed, yet still completely cover and coat the surface.

[0060] Therefore, the base coat paper or cellulose-based substrate may have a roughness lower than that of the substrate itself, for example, 180 ml / min Bentsen or less, for example, 150 ml / min Bentsen or less, for example, 130 ml / min Bentsen or less, for example, 120 ml / min or less, for example, 100 ml / min or less, for example, 80 ml / min or less, for example, 50 ml / min or less, for example, 30 ml / min or less, for example, 25 ml / min or less when measured according to ISO 8791:4.

[0061] A good cellulose-based substrate, in a coating method for industrially manufacturing the barrier coating structure of the present invention, in order to function well under executable high-speed conditions, on the coating surface (the "upper surface" or the "printing surface"), the Cobb 60 surface water absorption value measured according to ISO 535:2014 is 30 g / m 2 It can be below.

[0062] The Cobb 60 method according to ISO 535:2014 measures the water absorption rate of a cellulose-based substrate under standardized conditions, and in a sense, it is a measure of the "coating property" of the surface of the cellulose-based substrate, that is, the ability to be coated with an aqueous solution composition of a gas barrier polymer. If the surface absorbs too much solution before drying, the thinly applied wet coating will break and a continuous coating of the gas barrier polymer cannot be formed. Therefore, the Cobb 60 value is 30 g / m 2 less than, for example, 28 g / m 2 less than, preferably 25 g / m 2 It is preferably below.

[0063] Therefore, the surface of the upper surface of the cellulose-based substrate may preferably exhibit a Bentsen roughness value lower than 30 ml / min and a Cobb 60 absorption value of 25 g / m 2 or less.

[0064] In a further embodiment, the surface of the upper surface of the paper or cellulose-based substrate may exhibit a Gurley porosity value of greater than 1000 s / dl, for example greater than 2000 s / dl, according to Tappi T460 om-2. The advantage of the low surface porosity is that the amount of the aqueous solution of the gas barrier polymer absorbed by the cellulose-based substrate is reduced. Since the dispersion-coated aqueous composition of the base coating can be very thin, this can be important for the integrity of the coating and for the ability of the coating to form a smooth and uniform surface for receiving further coatings or layers thereon.

[0065] Thus, in a cellulose-based substrate suitable for being coated with a thin coating of an aqueous composition consisting of an oxygen barrier polymer, the number and size of the pores in the substrate should preferably be significantly reduced. By extensively purifying the pulp used in the manufacture of the substrate, the fiber bond strength is increased, and as a result, the porosity is decreased. Greaseproof paper is manufactured by such extensive purification and has a sufficiently low porosity to provide a grease barrier.

[0066] Thus, greaseproof paper has also been regarded as a potential substrate or carrier for additional gas barrier coatings. However, the resulting pulp has high dehydration resistance, requires a long time for the dewatering of the paper stock, is costly in the manufacturing process, and is not desirable in the repulping and recycling processes. The same applies to parchment paper, which obtains gelatinized fibers by passing through a sulfuric acid bath during manufacture, thereby reducing the dewatering and repulping of the fibers and further imparting an undesirable brittleness to the parchment paper. The same also applies to paper or films containing more than 50% by weight of fibrillated cellulose such as MFC or NFC, i.e., mostly. Incorporating fibrillated cellulose into a cellulose-based substrate is not very advantageous in the repulping process for recycling cellulose fibers, i.e., fibrous ones, from a laminate material containing the paper or cellulose-based substrate.

[0067] According to one embodiment, the cellulosic substrate for use in the present invention may be formed from cellulose fibers containing at least 50% by dry weight of a chemical pulp, such as kraft pulp or sulfite pulp, which is used to obtain a paper that is strong enough for downstream processes such as coating on high speed lines, as well as lamination and final packaging uses.

[0068] Sulfate / kraft pulp is widely produced in large quantities and may be preferred due to its advantages in improving repulping during recycling and general fiber dewatering. Sulfite fibers typically have a high proportion of refined fibers, which may have some adverse effects depending on the proportion and degree of refinement. Kraft pulp is preferred according to one embodiment of the present invention.

[0069] The cellulosic substrate may be formed from cellulose fibers consisting of 35-100%, such as 35-80%, such as 40-70%, softwood pulp by dry weight of the pulp used to form the high density paper, with the remaining portion of the pulp composition consisting of hardwood fibers and minor amounts of other fibers.

[0070] The benefits of including softwood pulp include improved runnability on the paper machine and increased strength / toughness properties of the resulting paper. A relatively high proportion of softwood pulp allows the cellulosic substrate to be dense enough without causing problems with dewatering during substrate production, and also allows for repulping during recycling. The degree of fineness of the fiber composition is further selected to promote both dewatering and repulping capabilities, while also promoting the formation of a dense paper with low porosity.

[0071] Therefore, although there are some base papers that have inherently excellent oxygen barrier properties, they are not very desirable as final materials for other reasons, such as low recyclability (repulpability), and it is required that the oxygen barrier properties be significantly enhanced by a coating material that is applied to the substrate surface, bonds well to the substrate surface, and interacts well with the substrate surface.

[0072] To have good mechanical properties for coating at high coating line speeds exceeding 300 m / min, for example exceeding 400 m / min, the cellulosic base material can have a tensile strength of 3 - 6 kN / m in the MD (machine direction) and 1.5 - 3.5 kN / m in the CD (cross direction). In the present disclosure, the tensile strength is measured in accordance with ISO 1924 - 3:2005. Thus, a higher tensile strength can indicate a paper base material useful for withstanding web handling forces during coating and lamination operations.

[0073] The cellulosic base material can further have a tensile strain of 1.4 - 3.5% in the machine direction and 2.1 - 6.0% in the CD direction.

[0074] The cellulosic base material can further have a tensile energy of 35 - 90 J / m in the MD direction 2 and 37 - 140 J / m in the CD direction 2 and can be.

[0075] The E modulus of elasticity of the cellulosic base material is 9500 - 12500 MPa in the MD direction and 4000 - 7000 MPa in the CD direction.

[0076] Preferably, beneficial barrier properties and recycling properties can be obtained without sacrificing tensile strength and other mechanical properties.

[0077] In order to provide barrier properties and / or good sheet resistance in a metallization coating, it has previously been found that vapor deposition coatings such as metallization coatings are coated to a thickness of only a few nanometers and first require a thin but defect-free base coating or a pre-coating of a smoothing polymer applied onto a paper or cellulose-based substrate. Polymers that function well as such base coating polymers may be selected from vinyl alcohol polymers and copolymers, which also have inherent gas barrier properties and are highly food-safe and environmentally sustainable both with regard to recyclability and in industrial coating and lamination processes. Such polymers are water-dispersible and / or water-soluble and are applied by an aqueous “dispersion coating” process or a so-called “liquid film coating” process. Polymers having a good smoothing effect are starch or modified starch. However, generally starch materials have significantly lower gas barrier properties than, for example, PVOH.

[0078] For the purpose of high-frequency induction heat sealing, it has recently been found that starch materials are significantly superior as a base coating for applying an induction-sensitive metallization layer. Starch materials provide better thermo-mechanical stability in the heat sealing operation, but also have a significant smoothing effect, so the initial roughness of the substrate surface may not be as important for the quality of the thin barrier coatings or metal coatings applied subsequently.

[0079] Suitable starch materials for such base coatings may be oxidized starches or modified starches suitable for aqueous dissolution at low or normal temperature, such as oxidized native potato starch, because such cold water-soluble starches do not form gels during production. Examples of such suitable starch materials include Etenia® or Solvicol® 1290 from Avebe in the Netherlands.

[0080] The base coating layer may be applied as a single coating or as two consecutive thin coatings.

[0081] Other polysaccharide materials can also function well as the base coating with only slight changes in the conditions of coating, coating, and drying. Other possible materials suitable for inclusion in the base coating may be thin coatings of cellulose ether materials that can be easily dispersed or solution-coated. The cellulose ether material may sometimes have a smoothing property when applied to a non-smooth paper or paperboard surface, and such materials provide a high-quality subsequent vapor deposition coating of metal. However, cellulose ether is not known to provide an oxygen barrier property and accordingly is less preferred than starch materials for the base coating. Suitable cellulose ether materials may comprise one or more compounds selected from the group consisting of methyl cellulose, ethyl cellulose, carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), hydroxypropyl methyl cellulose (HPMC), and sodium carboxymethyl cellulose (NaCMC).

[0082] The composition of the base coating may further contain inorganic particles or fillers such as talcum, kaolin, and nano-clays such as bentonite and montmorillonite. The amount of such inorganic material may be 1 to 40% by weight, for example 1 to 30% by weight, for example 1 to 20% by weight, for example 1 to 15% by weight, based on the solids content of the base coating composition.

[0083] The aqueous solution of the base coating composition may be uniformly applied to the surface of the upper surface of the web of the cellulose-based substrate by a roll coating method, providing a coating in an amount of 0.3 to 2 g / m 2 In an amount. If it is less than 0.3 g / m 2 , the starch has little effect of smoothing the cellulose substrate surface, and if it exceeds 2 g / m 2 , or 1.5 g / m 2Even so, the coating becomes difficult to dry, and it requires a lot of energy and time to evaporate water from the starch. 0.5 g / m 2 or more of starch can achieve a good smoothing effect, and a good balance between the quality and cost efficiency of the coating layer can be obtained with a coating layer of 0.5 - 0.8 g / m 2 . In many cases, since it is desirable to thicken the entire coating of the starch material, at least one additional coating step is added after the drying of the first coating layer is completed.

[0084] Therefore, the base coating may be applied in two sub - layers in two consecutive steps with intermediate drying. When applied as two sub - layers, each layer is preferably applied in an amount of 0.2 - 1 g / m 2 , for example 0.2 - 0.8 g / m 2 , for example 0.5 - 0.7 g / m 2 in terms of quantity, and a higher - quality total layer can be obtained from a smaller amount of the liquid base - coating material composition.

[0085] The two sub - layers of starch can each be applied in an amount of 0.2 - 1 g / m 2 . Since the starch - based coating can provide a very good smoothing coating with only one coating, the metal coating can obtain a sufficiently good quality with only such one base coating. As a result, due to the smoothness and high quality of the metal coating applied on the starch - based coating, it is sufficient to apply only a single gas - barrier coating as the top coating, and still very good gas - barrier properties and good high - frequency induction heat - sealing ability can be obtained as a whole.

[0086] Next, the barrier - coated cellulose - based of the present invention includes a step of depositing a metal coating on the first - applied base coating obtained from an aqueous solution coated with a heat - resistant polymer and dried by physical vapor deposition (PVD).

[0087] In the method of the present invention, the physical vapor deposition coating is a metallization coating, preferably an aluminum metallization coating.

[0088] Such a thin vapor-deposited metal coating layer has a nanometer thickness, that is, most preferably a thickness that can be counted in nanometers, for example, 5 to 500 nm (50 to 5000 Å), for example, 5 to 200 nm, more preferably 5 to 100 nm, for example, 5 to 50 nm.

[0089] Generally, if it is less than 5 nm, the barrier properties may be too low, and the sheet resistance of the metallization coating may be too high for the purpose of induction heating. Also, if it is 200 nm or more, for example, 100 nm or more, for example, 80 nm or more, for example, 50 nm or more, depending on the quality of the deposited coating, the flexibility of the barrier coating may decrease. Therefore, when applied to a flexible substrate, cracks are likely to occur. Also, since it is necessary to reduce the deposition coating speed, the cost also increases.

[0090] In one embodiment, with respect to the flexibility of the coated metallization coating and with respect to the coating operation efficiency, the metal vapor deposition coating is applied to a thickness of 10 to 200 nm, for example, 10 to 150 nm, for example, 10 to 100 nm, for example, 10 to 95 nm, for example, 10 to 80 nm, for example, 10 to 50 nm, which corresponds to less than 1 to 3% of the aluminum metal material present in a conventional thickness for packaging, for example, 6 to 9 mm thick aluminum foil.

[0091] Although the vapor-deposited metal coating requires significantly less metal material compared to metal foil, it only provides a low level of oxygen barrier properties and needs to be combined with an additional gas barrier material to provide a final laminate material with sufficient barrier properties. On the other hand, a gas barrier layer such as PVOH or EVOH may complement it, but this does not provide a water vapor barrier property and is rather sensitive to moisture.

[0092] Other examples of vapor deposition coatings include aluminum oxide (AlOx, Al2O3) and silicon oxide (SiOx) coatings. Generally, such PVD coatings may be more brittle and may not be well-suited for incorporation into packaging materials by lamination, while metallized layers, despite being made by PVD, may offer more suitable mechanical properties for lamination materials.

[0093] Typically, the metallized layer of aluminum also has a thin surface portion containing aluminum oxide that is normally and essentially formed towards the end of the metallization coating process.

[0094] The metallized coating of aluminum can be applied by physical vapor deposition to a sheet resistance value of 0.25 Ω□ to 0.75 Ω□, for example 0.4 Ω□ to 0.6 Ω□. For the purpose of induction heating sealing, the sheet resistance of the metallized coating needs to be as low as possible, but there is a practical lower limit within the possible range. So far, the optimal level is about 0.5 to 0.75 Ω□.

[0095] For the PVD coating process to function optimally, the moisture content of the paper or cellulose-based substrate needs to be maintained at 4 to 8%. If the paper substrate is too dry, the longitudinal edges will curl towards each other, causing problems in coating and handling by the method of the present invention. On the other hand, if the moisture content is too high, the vapor deposition coating operation may not function properly, and it may not be possible to obtain a high-quality coating.

[0096] In one embodiment, the aluminum metallized layer is applied with an optical density (OD) of 1.8 or more, for example 1.8 to 4, for example 2 to 3.5, for example 2.5 to 3.5. If the optical density is less than 1.8, the barrier properties of the metallized film may be too low, and if the OD is less than 2.0, the sheet resistance may be too high. If the OD exceeds 4, the deposited metal layer becomes more sensitive to mechanical stress and the flexibility decreases, so cracks and defects may form, and the oxygen barrier properties and induction heat sealing properties may be impaired.

[0097] In some embodiments, the metal coating may be deposited as two consecutive vapor deposition coatings to enhance quality and flexibility.

[0098] Optical density is measured in the manufacturing process using a densitometer, i.e., a device that uses the principle of diffused light transmission (Macbeth, Tobias, etc.). This device is suitable for measuring the optical density value of a film coated with aluminum metallization. The measurement accuracy and precision are high, within a measurement range of 0 to 6.60 OD, approximately + / -0.2 OD and approximately + / -0.01 OD, respectively.

[0099] In laboratory measurements, a spectrophotometer may be used to measure the light transmittance across the entire visible spectrum (380 - 800 nm). Optical density is calculated from the light transmittance (T) value at 560 nm according to the formula OD = -log10 (I1 / I0), and the obtained value has the same accuracy (+ / -0.2 OD) and is equivalent to the value of a light transmission densitometer.

[0100] The metallization coating is further coated with a thin aqueous composition containing a gas barrier polymer. The gas barrier polymer should also exhibit a certain degree of heat resistance so that adjacent heat - sealable material layers do not melt or deteriorate during induction heat sealing. Thus, the gas barrier polymer may have a melting point higher than that of the material that melts and is heat - sealed. The gas barrier polymer of the top - coat aqueous composition may preferably be a polymer or copolymer based on vinyl alcohol monomers, such as polyvinyl alcohol (PVOH), ethylene - vinyl alcohol copolymer (EVOH), and modified PVOH and EVOH copolymers capable of forming an aqueous solution, selected from these. Such polymers are modified, for example, in some cases by the addition of carboxyl functional groups.

[0101] In one embodiment, the water-soluble gas barrier polymer is PVOH. For example, PVOH of the Poval (registered trademark) type by Kuraray provides good film-forming properties, gas barrier properties, cost efficiency, food compatibility, and odor barrier properties.

[0102] In another embodiment, the gas barrier polymer is a water-soluble EVOH with a low ethylene monomer content, such as Exceval (registered trademark) type EVOH by Kuraray. The advantage of using an EVOH polymer as a gas barrier material is that the ethylene content supports resistance to humidity, and for example, the oxygen barrier properties are better maintained even at a high relative humidity such as 80% RH. This is particularly relevant for the packaging of oxygen-sensitive liquids, such as the carton laminate packaging of liquid foods.

[0103] Conventional EVOH polymers are usually intended for extrusion molding and cannot be dispersed or dissolved in an aqueous medium to produce the following thin liquid film coating barrier films with a thickness of 4 g / m 2 The water-soluble EVOH contains a large amount of vinyl alcohol monomer units to be water-dispersible, and its properties are as close as possible to those of the liquid film coating grade of PVOH. Also, such water-soluble EVOH exhibits a melting point higher than that of the material layer to be heat-sealed, and thus has sufficient thermal stability to support a metallized coating and withstand an induction heat-sealing operation.

[0104] On the other hand, the extruded EVOH layer cannot replace the EVOH coated with a liquid film. This is because EVOH is essentially less similar to PVOH than the EVOH grade for dispersion / solution coating, and it is not possible to obtain sufficient adhesion to the adjacent layer by applying it in an efficient manner by melt extrusion coating or melt extrusion lamination. The melt coextrusion coating with polyethylene or a tie-layer polymer mainly composed of ethylene is technically difficult due to the difference in melt viscosity and incompatibility.

[0105] PVOH-based gas barrier compositions function best when the degree of saponification of PVOH is at least 98%, preferably at least 99%. However, PVOH with a low degree of saponification can also provide oxygen barrier properties. The PVOH of the most advantageous quality and grade for the method of the present invention is Poval® 6-98.

[0106] In a further embodiment, the PVOH can be Poval® 15-99.

[0107] In yet another embodiment, the PVOH can be Poval® 6-96, but the oxygen barrier provided by this grade may be slightly lower.

[0108] EVOH grades suitable for coating by the method of the present invention include Exceval® 4104AQ, which has coating properties similar to Poval® 6-98, and Exceval® HR-3010, which has coating properties similar to Poval® 15-99.

[0109] Possible additives in the barrier top coating composition may be polymers or compounds having functional carboxylic acid groups, particularly for the purpose of improving the water vapor and oxygen barrier properties of the PVOH top coating and, in particular, for the purpose of improving the adhesion of the top coating to the metallized coating on the surface of the coated paper substrate. Preferably, such polymers having functional carboxylic acid groups are selected from ethylene acrylic acid copolymers (EAA) and ethylene methacrylic acid copolymers (EMAA) or mixtures thereof. The EAA or EMAA copolymer can be included in the barrier top coating in an amount of 1 to 49% by weight, such as 1 to 40% by weight, such as 1 to 35% by weight, such as 1 to 30% by weight, such as 1 to 25% by weight, such as 1 to 20% by weight, such as 1 to 15% by weight, based on the dry coating weight.

[0110] In one embodiment, the topcoat may be applied as two consecutive layers. The first coating layer has a high proportion of EAA adhesive polymer and the remainder consists of PVOH. The second coating layer has a high proportion of PVOH or consists only of PVOH. Thus, both good adhesion to the metallized surface and good gas barrier properties can be provided at an optimal level by the topcoat layer.

[0111] In one embodiment, such a barrier layer mixture may consist essentially of PVOH, EAA and an inorganic layered compound. For example, an inorganic layered compound such as exfoliated nanoclay particles such as talcum, kaolin or bentonite may be included in an amount of about 1% to about 10% by weight based on the dry coating weight.

[0112] Therefore, it is more preferable to use a barrier topcoat from a pure PVOH or EVOH composition, but advantageous results can also be obtained with gas barrier coatings containing additional additives as described above.

[0113] By a roll coating method, it is uniformly applied to the surface of the upper side of the web of the metallized cellulose-based substrate, providing a coating in an amount of 0.5 to 2 g / m 2 , preferably 0.5 to 1.5 g / m 2 of dry weight. If it is less than 0.5 g / m 2 , only insufficient gas barrier properties may be obtained. If it exceeds 2 g / m 2 , the energy cost is high and the time available for evaporating water is short (due to the high coating line speed), so the coating may not be cost-effective for the packaging laminate. An oxygen barrier at a recognizable level by PVOH is achieved at 0.5 g / m 2 or more, and a good balance of barrier properties, coating layer quality and cost is achieved with a coating layer of 0.5 to 2 g / m 2 . In many cases, since it is desired to thicken the entire coating of the gas barrier polymer, at least one additional coating step is added after the drying of the first coating layer is completed.

[0114] Therefore, the heat-resistant gas barrier top coating may be applied in two sub-layers in two consecutive steps with intermediate drying. The two sub-layers may have different compositions or mixing ratios of vinyl alcohol-based polymers and other polymers and additives. When applied as two sub-layers, each layer is preferably applied in an amount of 0.2 to 1.5 g / m 2 , for example, in an amount of 0.2 to 1 g / m based on dry weight 2 , and a higher quality total layer can be obtained from a smaller amount of the liquid gas barrier composition. Therefore, the two sub-layers of PVOH may each be in an amount of 0.25 to 1 g / m 2 , for example, each in an amount of 0.3 to 0.8 g / m 2 , for example, each in an amount of 0.5 to 0.8 g / m 2 and may be applied in an amount of.

[0115] Also, the starch-based coating may be applied twice in such a continuous coating with intermediate drying in between, but since the starch-based coating can provide a very good smoothing coating with only one coating, the metal coating can obtain sufficiently good quality by performing such a base coating only once. Furthermore, due to the smoothness and high quality of the metal coating applied on the starch base coating, very good gas barrier properties and high frequency induction heat sealing ability can be obtained by applying only a single gas barrier coating as the top coating.

[0116] The heat-resistant gas barrier top coating composition may further contain a low amount of an inorganic layered compound, such as talcum, kaolin or exfoliated nanoclay particles, such as bentonite, in an amount of 1 to about 20 wt%, for example 1 to about 15 wt% based on the dry coating weight. In such a case, the barrier layer may contain about 99 to about 90 wt% of a polymer based on the dry coating weight.

[0117] The amount of the wet coating to be applied may be about 10 times that of the solid target coating applied and dried. Thus, the amount of the wet coating of starch or PVOH to be applied is about 5 to about 20 g / m 2 , for example, 5 to about 10 g / m 2 . Therefore, in the drying step, it is necessary to evaporate a considerable amount of water at a high coating speed. If there is too much moisture, subsequent coating and post-lamination operation steps will be hindered, defects will occur in the applied barrier coating, the quality of the coating will be impaired, and the advantageous properties provided by the finally barrier-coated substrate may be reduced. Therefore, it is important to ensure that there is not too much moisture remaining on the coated substrate or absorbed by the substrate.

[0118] An industrially feasible, i.e., high-speed method suitable for applying the base coating and the aqueous solution composition of the polymer for the heat-resistant gas barrier top coating of the present invention is, in a broad sense, any suitable wet roll coating method such as gravure roll coating, smooth roll coating, and reverse roll coating or gravure coating. In an advantageous embodiment of the method of the present invention, the aqueous solution composition of the polymer is applied by reverse gravure coating. The reverse gravure coating method has been proven to make it easier to smooth the coated surface compared to the forward gravure coating method, which functions more as a printing method on the surface of the gas barrier polymer rather than a full coating method.

[0119] To adapt to the roll coating method, the solid content of the water-soluble polymer should be 5 to 15% by weight and can be adjusted to an appropriate solid content according to the polymer selection and coating speed. The solid content in the method of the present invention is more preferably 7 to 13% by weight, for example 9 to 13% by weight, preferably 10 to 12.5% by weight. At the above 10% solid content, it has been proven that the highest quality coating, that is, a uniform, smooth and substantially defect-free coating can be obtained by the reverse gravure coating method.

[0120] The viscosity of the aqueous solution of the starch-based coating or PVOH gas barrier polymer to be coated needs to be 10 to 120 MPa·s, for example 50 to 100 MPa·s. This enables optimal pickup of the gas barrier solution by the gravure roller and transfer to the substrate surface at high-speed line coating speeds exceeding 300 m / min, for example exceeding 400 m / min, or exceeding 600 m / min.

[0121] The gas barrier composition may also contain additives such as a dispersion stabilizer, and the amount thereof is preferably about 1% by weight or less based on the dry coating. The total dry content of the composition is preferably 5 to 15% by weight, more preferably 7 to 12% by weight.

[0122] The aqueous solution composition of the base coating or the heat-resistant gas barrier top coating may be heated and applied at a temperature of 60 to 80°C. By heating to such a warm temperature, the risk of bubbles generated during coating is reduced.

[0123] To further reduce the bubbles or bubble formation in the aqueous polymer solution, an antifoaming agent may be added. A preferred antifoaming agent is n-octanol, which is safe for food and has been proven to exhibit excellent effects in a smaller amount, for example 0.01 to 0.1% by weight of the solution, for example about 0.05% by weight, compared to other tested agents. Other tested agents have been reported to degrade PVOH and increase the OTR of the applied and dried PVOH coating.

[0124] Since the wet coating of the aqueous solution of the gas barrier polymer is very thin and can be damaged by overheating, it is advantageous to dry it consistently only at low temperatures.

[0125] The drying process may be carried out by a hot air dryer, whereby moisture evaporates and is blown off from the surface of the substrate by air convection. The substrate temperature is kept constant at a temperature of less than 95°C, for example less than 85°C, for example 75 - 85°C, for example about 80°C when passing through the dryer. Drying may be partially assisted by radiant heat from an infrared IR lamp, in combination with hot air convection drying at a high line speed, if necessary.

[0126] The more water is added by the wet-coated coating, the more water needs to be evaporated in a high-line-speed dryer. There is a balance between the solid content in the aqueous coating and the length of the dryer section to make the dry thin-layer coating as little as 1 - 2 g / m 2 It is necessary to avoid drying too fast due to the risk of film formation, and also to avoid drying too slowly because the absorption into the paper is too high, resulting in a thin surface film thickness or damage to the coating (defects). Therefore, it is necessary to control the evaporation of moisture so that the surface temperature of the substrate does not become too high and film formation does not occur.

[0127] Such a balanced setting may be specific to each coating line and paper / coating combination.

[0128] The barrier-coated paper or cellulosic substrate obtained according to the method of the present invention provides excellent low OCTR and, surprisingly, also exhibits resistance to degradation of low OCTR (i.e., no or very little increase in low OCTR) from a high relative moisture content of 80% (RH), even though the gas barrier coating is disposed inside the metallized coating of a laminate packaging material and is more exposed to moisture vapor migration from a liquid or wet product in a filled packaging container. Thus, it has proven unexpectedly highly suitable for lamination into laminate packaging materials and further for creasing and sealing such laminate materials into packages.

[0129] The laminate packaging material comprising the barrier-coated cellulosic substrate further comprises a first outermost protective material layer and a second innermost liquid-tight heat-sealable material layer. The second innermost liquid-tight heat-sealable material layer may comprise or consist of a thermoplastic polymer such as a polyolefin polymer. The first outermost protective material layer may be transparent so that the decorative pattern printed on the outside of the bulk layer is visible. It may also comprise or consist of a thermoplastic polymer such as a polyolefin polymer.

[0130] The carton-based laminate packaging material for liquid food packaging may further comprise a bulk layer of paper or paperboard, a first outermost protective material layer, a second innermost liquid-tight heat-sealable material layer, and said barrier-coated paper or cellulosic substrate positioned inside the bulk layer of paper or paperboard, towards the inside of a packaging container made from the packaging material, between the bulk layer and the second innermost liquid-tight heat-sealable material layer.

[0131] In one embodiment, the carton-based laminate packaging material thus comprises a bulk layer of paper or cardboard, a first outermost liquid-tight and heat-sealable polyolefin layer, a second innermost liquid-tight and heat-sealable polyolefin layer, and, inside the bulk layer of paper or cardboard, between the bulk layer and the innermost liquid-tight and heat-sealable polyolefin layer, towards the inside of the packaging container made from the packaging material, the barrier-coated paper or cellulose-based substrate arranged therebetween.

[0132] The bulk layer of paper or cardboard used in the present invention usually has a thickness of about 70 μm to about 600 μm and a basis weight of about 65 to 500 g / m 2 , for example, 100 to 400 g / m 2 , preferably about 200 to 300 g / m 2 and may be a conventional paper or cardboard of appropriate packaging quality.

[0133] When using the resulting laminate material as a pouch package, a thin paper layer may be used for the barrier-coated paper substrate and the bulk layer, and these together create the bulk strength or stability of the paper laminate. In such a case, the basis weight of the additional "bulk" paper is 40 to 64 g / m 2 , for example, 40 to 55 g / m 2 and the basis weight of the barrier-coated paper substrate is 40 to 55 g / m 2 .

[0134] For the low-cost aseptic long-term packaging of liquid foods, thinner packaging laminates with thinner paper core layers can be used. The packaging containers made from such packaging laminates are not fold-formed but rather resemble pillow-shaped flexible pouches. Papers suitable for pouch packages usually have a basis weight of about 50 to about 140 g / m 2 , preferably about 70 to about 120 g / m 2 , more preferably 70 to about 110 g / m 2has a basis weight. The barrier-coated paper or cellulosic substrate of the method of the present invention may itself impart some stability to the laminate material, so the paper layer corresponding to the "bulk" layer may be even thinner and interact with the cellulosic substrate barrier-coated in a sandwich interaction to still overall have the desired mechanical properties to produce a laminated packaging material.

[0135] The barrier-coated paper or cellulosic substrate may be bonded to the bulk layer by an intermediate adhesive or a thermoplastic polymer bonding layer, thereby bonding the uncoated surface of the barrier-coated paper to the bulk layer. According to one embodiment, the bonding layer is a polyolefin layer, for example, in particular, a layer of a polyethylene-based polyolefin copolymer or blend containing mostly ethylene monomer units. The bonding layer may bond the bulk layer to the barrier-coated cellulosic substrate by melt-extrusion laminating a bonding polymer layer between the web of the bulk layer and the web of the cellulosic substrate and pressing the three layers together simultaneously while advancing through a lamination roller nip, thus providing a laminate structure by extrusion lamination.

[0136] In another embodiment, the barrier-coated cellulosic substrate may be wet-coated with an aqueous dispersion of an adhesive composition containing an adhesive polymer binder on one surface of the web to be laminated and bonded to the bulk layer by pressing the two paper webs together while advancing through a lamination roller nip, thus providing a laminate structure by wet lamination. The moisture of the aqueous adhesive composition is absorbed by the fibrous cellulose network of the two cellulosic layers and partially evaporates over time in the subsequent lamination process. Therefore, a forced drying step is not necessary.

[0137] The aqueous adhesive polymer binder may be selected from the group consisting of acrylic polymers and copolymers, starch, starch derivatives, cellulose and polysaccharide derivatives, polymers and copolymers of vinyl acetate and vinyl alcohol, and copolymers of styrene-acrylic latex or styrene-butadiene latex. To optimize the environmental and sustainability profile as much as possible, an adhesive binder derived from plant or non-fossil resources is desirable.

[0138] Thermoplastic plastics suitable for the outermost and innermost heat-sealable liquid-tight layers are polyolefins such as homopolymers or copolymers of polyethylene and polypropylene, preferably polyethylene, more preferably polyethylene selected from the group consisting of low-density polyethylene (LDPE), linear LDPE (LLDPE), single-site catalyst metallocene polyethylene (m-LLDPE), and blends or copolymers thereof. According to one embodiment, the first outermost protective layer and liquid-tight layer are LDPE, and the second innermost heat-sealable liquid-tight layer is a blend composition of m-LLDPE and LDPE to obtain optimal lamination and heat-sealing properties.

[0139] The same thermoplastic polyolefin-based materials listed for the first outermost layer and the second innermost layer, particularly polyethylene, are also suitable as an adhesive layer inside the laminate material, i.e., between the bulk layer or core layer such as paper or paperboard and the barrier film or sheet. In one embodiment, the thermoplastic internal bonding layer may be a polyethylene layer, such as a low-density polyethylene (LDPE) layer.

[0140] In a further embodiment, the second innermost liquid-tight and heat-sealable polyolefin layer is a pre-manufactured film made of the same or a similar polyolefin as described above, i.e., LDPE, LLDPE, and / or m-LLDPE, such as a biaxially oriented film comprising at least one layer predominantly occupied by an LLDPE polymer, in order to improve the robustness of the mechanical properties of the packaging material. By the manufacturing process in film blowing and film casting operations, and optionally subsequent film orientation operation processes, the polymer of such a film acquires properties different from those possible with (co)extrusion-coated polyolefin layers. Such pre-manufactured, preferably oriented, polymer films can greatly contribute to the mechanical robustness of the laminate packaging material and the mechanical strength and packaging integrity of the packaging containers formed and filled from the laminate packaging material.

[0141] According to an alternative embodiment, a suitable adhesive layer or tie layer inside the laminate material, such as between a bulk layer or core layer and a barrier-coated cellulosic substrate, or between an outer heat-sealable layer and a barrier-coated paper substrate, is a so-called adhesive thermoplastic polymer, e.g., a modified polyolefin based mainly on an LDPE or LLDPE copolymer, or a graft copolymer having functional group-containing monomer units, such as carboxyl functional groups or glycidyl functional groups (i.e., ethylene acrylic acid copolymer (EAA) or ethylene methacrylic acid copolymer (MAH)). For example, (meth)acrylic acid monomer or maleic anhydride (MAH) monomer (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 a modified polymer or adhesive polymer is a so-called ionomer or ionomer polymer. Preferably, the modified polyolefin is ethylene acrylic acid copolymer (EAA) or ethylene methacrylic acid copolymer (EMAA).

[0142] The laminate packaging material produced in accordance with the above provides good adhesion and interaction between adjacent layers in the laminate structure, as well as good quality of the gas barrier coating and vapor-deposited barrier coating, thereby providing good integrity when transformed into a filled packaging container. In particular, in packaging liquids and moist foods, an important finding was that the interlayer adhesion within the laminate packaging material, as well as the oxygen gas barrier properties, are maintained even under moist packaging conditions.

[0143] According to a further embodiment, a packaging container formed from the laminate packaging material is partially sealed, filled with a liquid or semi-liquid food product, and then sealed by sealing the packaging material itself, optionally in combination with a plastic opening or package top.

[0144] In conclusion, the improved barrier properties provided by the barrier-coated cellulosic substrates defined in the present invention and laminate packaging materials comprising the same result in robust and reliable packages for packaging liquid foods for long-term storage and aging. The laminate packaging material structure is more suitable for forming into a folded and molded package due to both the improved adhesion between the substrate and the barrier material coating and the improved contribution of the barrier-coated substrate itself to the gas barrier properties, which is believed to be due to the good bonding and adhesion between the barrier coating layer and the surface of the barrier-coated cellulosic substrate.

[0145] ( Examples and Descriptions of Preferred Embodiments ) Preferred embodiments of the present invention will now be described with reference to the drawings. [Brief explanation of the drawings]

[0146]

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Embodiments for Carrying Out the Invention

[0147] Examples As described at the beginning, the international patent application publication WO2011 / 003565A1 discloses a non-aluminum foil laminate packaging material comprising a base-coated and metallized kraft paper substrate for the purpose of induction heat-sealing the innermost layer of a thermoplastic polymer facing the inside of a packaging container. In particular, in order to obtain good gas barrier properties, a base coating of PVOH and additional nanoclay particles in an aqueous composition is recommended, and further, it is recommended to apply an aluminum metallized PVD vapor deposition coating thereon. In order for the base coating to function well in the induction heat-sealing of the laminate packaging material, the polymer or binder of the base coating has a higher melting point than the innermost thermosealable polymer layer. Examples of equivalent or similar base coating polymers having induction heating durability include starch, other polysaccharides, PVOH, water-dispersible EVOH, polyvinylidene chloride, and the like.

[0148] Recent research has revealed that a PVOH base coating may ultimately not be the optimal choice among the listed examples for the purpose of induction heat-sealing. The current hypothesis is that PVOH may not have complete heat resistance under severe induction heating conditions, so there is a possibility that the metallized layer cannot remain fully intact without defects to enable sealing. Furthermore, it has been found that if starch is used as an alternative as the base coating for metallization, the "window" of the output that enables induction heating sealing can be widened even for thicker materials, that is, good induction heating sealing is possible both at low output settings and high output settings.

[0149] Examples Example 1 Various base coating materials were applied to a cellulose-based substrate, and the heat-sealing ability and oxygen barrier performance by high-frequency induction heat-sealing were tested.

[0150] Two different samples of barrier-coated cellulose-based substrates were produced. In the first sample, the density was about 950 kg / m 3 , and the basis weight was about 40 g / m 2, a base coating of Kuraray's PVOH (Poval (registered trademark) 6-98) was applied to a paper substrate with a surface roughness of less than 200 ml / min vent cent. In the first sample, the PVOH base coating was applied to the base paper as two consecutive coatings of approximately 0.7 g / m 2 .

[0151] In the second sample, cold water-soluble starch was applied as a base coating to the same paper substrate, forming two consecutive coatings of approximately 0.5 - 0.6 g / m 2 .

[0152] Two samples of the base-coated paper substrate were further metallized by physical vapor deposition, resulting in a sheet resistance of the metallized coating of approximately 0.5 Ω□ (ohm / square), and then laminated into a laminate structure with a basic structure.

[0153] / / LDPE outer layer (12 g / m 2 ) / cardboard 80 mN / bonding layer blend LDPE + mLLDPE (15 g / m 2 ) / Barrier-Coated Paper Substrate / adhesive polymer EAA (6 g / m 2 ) / LDPE (13 g / m 2 ) / biaxially oriented LLDPE film (18 μm) / /

[0154] When forming the laminate packaging material into a tubular packaging container, as described in relation to the above introduction section and Figure 6 below, the longitudinal ends of the web are continuously arranged to form overlapping longitudinal seal areas and are joined to the "LS" area sealed longitudinally along the formed tube by simultaneously applying heat and pressure. When heat is applied through the metallized aluminum layer by high-frequency induction heating, small defects may occur in the form of small holes, and non-uniformity may occur in the metallized coating.

[0155] Furthermore, when reforming the tube into individual packages, the tube is sealed transversely and the "pillows" of the formed packages are separated from the tube. Since the longitudinal seal is further involved in the transverse seal (by intersecting), a double overlap region "LS-TS" is created, and in this region, because the materials overlap thickly, defects are more likely to occur during the heat sealing operation. Here, defects may occur especially in relation to the longitudinal edges of the overlapping materials. In this case, the edges of the thick cardboard exert great stress on the layers and coatings of the adjacent and surrounding materials, which are layers considerably thinner than the cardboard. Since the stress is intensified by the application of induced current, heat, and pressure, defects mainly occur in the metallization coating located at the position of the cardboard edge.

[0156] The occurrence of fine traces, thinness, or cracks in the metallization coating at the longitudinal end position of the laminate packaging material can be visually recognized as lit traces by exposing the packaging material from this region to backlight, for example, by placing the flat packaging material on a light box with strong light.

[0157] Figure 7a shows a cross-section of the transverse seal region of a folded tube including a longitudinal overlap seal on one side. Thus, it shows how the longitudinal edges 71, 72 overlap and the positions of the most sensitive locations 73, 74 in the transverse seal of the LS (longitudinal seal) region, i.e., the LS-TS region, where such light marks may be generated in the metal coating. It also shows how the flat longitudinal seal strip 75 of the polymer is arranged and sealed. Along one of the edges, i.e., the so-called "LS-SA" (meaning LS strip application) edge 73, it is sealed to the polymer layer inside the packaging material to cover the exposed edge 73 of the cut material of the overlap edge inside the tube. When the tube is sealed transversely, the side with the LS overlap is sealed to the opposite side 76 of the tube. Thus, the folded edge of the transversely sealed tube is outside the drawing and is not shown here.

[0158] Figure 7b shows such fairly large visible light marks 77, 78 corresponding to the positions 73 and 74 in Figure 7a, which are visible when looking at a flat material against strong backlighting. Such marks can interfere with the induction heating process and cause defective products or non-uniform seal zones, and thus can affect the quality of heat seals, even if they are much smaller. The quality of the LS-TS area may be visually inspected for the occurrence of such marks by backlight illumination.

[0159] To simulate the stress during the overlap seal at the longitudinal seal part (LS) of the laminate material under the conditions of the heat seal operation in the filling machine, two laminate sample structures were heat-sealed to an elongated strip-shaped material with a pilot device respectively.

[0160] The laminate material samples tested in this way were exposed to different high-frequency induction power settings of 1500 W, 2000 W, and 2500 W with a seal pressing force of 12 kN and a time of 200 ms. The highest output of 2500 W exceeded the realistic conditions and was used to apply additional stress to the material and the seal operation. The strips of heat-sealable polymer material had three different thicknesses, and were applied inside the material of each sample and heat-sealed to evaluate the robustness of the material when heat-sealing at each of the three different power levels. The thickness of the strips was 0.25 - 0.5 mm.

[0161] To evaluate the seal and the quality of the material in the most difficult part of the heat-sealed packaging material, i.e., the seal in the LS-TS area, the sealed area was visually inspected and the number of visible light marks was recorded at different power settings of the heating inductor for sealing the transverse seal. The number of visually identified marks on the metallization coating of the LS overlap seal at different power levels is shown in (Table 1). Generally, for a specific material, when the power level is high and the material is thick, at least some visible marks are generated and the number of marks on the metallization coating is larger than when the power is low and the thickness is thin.

[0162] Two laminated sample structures were also folded, filled into a packaging container filled with water by a filling machine, and sealed. The oxygen transmission rate of the packaging (filled, empty, dry) was measured at 0.2 atm (ambient air contains 21% oxygen) according to ASTM F1307-14. The unit is cm 3 / package / 24 hours.

[0163] In the OTR measurement, the package is attached to a special holder and the inside of the package is purged with nitrogen. The outside of the package is exposed to the environment surrounding the device. When oxygen permeates through the package and enters the nitrogen carrier gas, it is carried to a coulometric sensor. The sensor reads how much oxygen is leaking into the nitrogen gas inside the package.

[0164] The number of visible marks confirmed in the LS-TS region and the oxygen transmission rate of the package made from the laminate sample of the above barrier-coated cellulosic substrate are shown in (Table 1).

[0165]

Table 1

[0166] The packages manufactured according to Comparative Sample 1 had better oxygen gas barrier properties, and the measured oxygen transmission rate was higher for the barrier coating sample having only a starch base coating (i.e., the barrier against oxygen permeation was low). On the other hand, the laminate material sample by Sample 1 had fewer traces generated in the metallization coating during the lateral induction heat sealing operation. From these results, it was concluded that starch as a base coating provides better stability in the step of applying heat to seal the internal polymer, particularly in sensitive areas where the thin metallization coating is prone to trace formation. However, from the perspective of gas barrier, starch is less preferable than PVOH.

[0167] Example 2 To explore further possibilities, experiments were conducted to further test the heat-sealing ability by high-frequency induction and the oxygen barrier performance for various barrier coating layer configurations in which the same cellulose-based substrate as used in Example 1 was coated with coatings of approximately the same amount and thickness as in Example 1.

[0168] Six different barrier coatings were applied to the paper substrate.

[0169] Each of the barrier-coated papers was laminated into a laminated structure having the following basic structure.

[0170] / / Outer LDPE (12 g / m 2 ) / Paperboard 80 mN / Bonding layer blend LDPE + mLLDPE (15 g / m 2 ) / Barrier-coated paper substrate / Adhesive polymer EAA (6 g / m 2 ) / LDPE (13 g / m 2 ) / Biaxially oriented LLDPE film (18 μm) / /

[0171] Six laminate material samples were composed of the following barrier-coated paper substrates.

[0172] Comparative Sample 2: Barrier-coated paper having a continuous two-layer base coating layer of Poval (registered trademark) 6-98 PVOH under a metallized coating, which is essentially the same as Comparative Sample 1 in (Table 1).

[0173] Comparative Sample 3: Similar to Comparative Sample 2, but with a three-layer (each layer having the same thickness and a total thicker amount of PVOH) continuous base coating of Poval (registered trademark) 6-98 PVOH under the metallized coating.

[0174] Comparative Sample 4: Similar to Comparative Sample 3, but the first base coating layer is a PVOH coating layer of the same thickness (0.7 g / m 2) and the other two coating layers are starch with a coating amount of about 0.5 to 0.6 g / m 2 .

[0175] Comparative Sample 5: Similar to Comparative Sample 4, but the two first base coating layers are PVOH coating layers with the same thickness (0.7 g / m 2 ).

[0176] Comparative Sample 6: Basically the same as Sample 1 in (Table 1), but on the opposite side of the paper substrate, two consecutive coatings of PVOH with the same grade and amount as in the other comparative examples above are applied.

[0177] Sample 2: Basically the same as Sample 1 in (Table 1), but on top of the metallized coating, as a top coating, a single coating of PVOH with the same grade and amount (0.7 g / m 2 ) is applied.

[0178] The laminate sample structure was folded and filled and sealed in a packaging container filled with water. The empty packages were evaluated in the same manner as in Table 1 for the quality of the lateral heat seal in the LS area (LS-TS) and the oxygen transmission rate.

[0179] The oxygen transmission rate of the packages (filled, empty, dry) was measured at 0.2 atm (the oxygen content of the ambient air is 21%) in accordance with ASTM F1307-14. The unit is cm 3 / package / 24 hours, and the conditions are 23 °C and 50% RH.

[0180] For OTR measurement, the packages are attached to a special holder, the inside of the packages is purged with nitrogen, and the outside of the packages is exposed to the environment surrounding the apparatus. When oxygen permeates through the package and enters the nitrogen carrier gas, it is carried to a coulometric sensor. The sensor reads how much oxygen is leaking into the nitrogen gas inside the package.

[0181] In the tested samples, the oxygen transmission rate values and the number of visible marks in the LS-TS region obtained from each of the three different power settings are shown in (Table 2).

[0182]

Table 2

[0183] Among the various variations of adding the PVOH gas barrier material to the barrier coating configuration for the purpose of improving the oxygen barrier properties, in Samples 1 - 6 of (Table 2), the configuration including the top coating of PVOH seems to be the most effective. Furthermore, unexpectedly, the HFIH seal properties for withstanding higher power and induced heat stress are also further improved.

[0184] It can be concluded that only one of the laminate material samples, namely Sample 2, actually achieved both good barrier properties and good heat seal in the LS-TS region. This is important for the barrier performance and seal performance of a rectangular-folded carton laminate package. A base coating of a material such as starch with smoothing and relatively high heat resistance is thought to provide a better base enabling a barrier layer structure with high quality and performance in both induction heat sealing and oxygen barrier performance.

[0185] Example 3 To detect small pinholes, weakening parts, and defects formed during heat sealing in one or more polymer layers on the inner side of the metallization coating, i.e., the side facing the filled product, a method of applying a high voltage and changing it step by step is used between the electrodes and the conductive layer arranged in the inner region of the laminate packaging material, i.e., the aluminum metallization coating. If there are slight signs of weakening, holes, or cracks in the polymer layer, such as "thinning" (i.e., regions or spots thinly covered with a thin polymer material), and contact can occur between the filled liquid or wet product and the metallization coating, a recordable "dielectric breakdown", i.e., a breakdown of the voltage, will occur between the electrode and the metallization coating, which may appear as a slight arc between the electrode and the metal coating. The voltage gradually rises from an initial low value towards a predetermined high value, and there is a value during this process that can cause a dielectric breakdown recordable with an oscilloscope. Alternatively, by detecting a "light spark" through the weak points of the polymer layer with some light detector, the "thinning" or weakening of the material can be detected. The increase in voltage applies stress to the metal coating and the adjacent layer of the laminated material, and if the material is thinned, the breakdown of the voltage will occur earlier (when the applied voltage is low). For this reason, the material is thinned or further damaged by the voltage. In this way, thinning or small weakening of the material in a very small area can also be observed.

[0186] Such a lamp-type high voltage (RHV) method can be used to detect weaknesses in the inner polymer layer along any region of the packaging material, for example, along the longitudinal seal region (LS).

[0187] The RHV detection method used in different regions of similar packaging materials (having a conductive layer of thicker aluminum foil) is described and disclosed in International Patent Application Publication WO2012 / 091661A1, and its principle is explained in more detail.

[0188] Therefore, to evaluate the quality of the polymer coating in the LS region outside the LS-TS region and detect defects, the RHV test method is used. When it is found that the breakdown voltage is high enough, the power setting is likely to be actually feasible for the high-frequency induction heat sealing of the material to be tested. In this way, it is possible to explore and verify the range from the lowest possible power setting to the highest power setting, and within this range, satisfactory seal quality and seal strength can be achieved, and no defects will be formed in the internal polymer material or metallization coating.

[0189]

Table 3

[0190] In the evaluation of the RHV results, rankings from 1 to 3 were used to investigate the feasible power settings and windows for the induction heating sealing operation. "1" means that the RHV value at breakdown is rarely lower than about 2 kV. "2" means that the RHV was not measured because the material concept was excluded for other reasons. "3" means that the RHV value at breakdown is often less than 2 kV.

[0191] Each heat seal power setting where the rank of RHV was "1", i.e., the heat seal power setting with less initial (low) break of voltage, and thus the heat seal power setting with fewer weaknesses inside the heat seal and the polymer layer material, contributes to the determination of the "power window" for heat sealing of the test material. When the heat seal power window is wider, i.e., determined to consist of a wider range of power settings for which the tested packaging material obtains a rank 1 in the RHV test, the heat seal process can be more robust around the predetermined power setting of the filling and sealing machine system using that specific material. Therefore, the evaluation of the width of this heat seal power window can indicate the "heat sealability" of the material in different seal areas of the package. The width of the power window (in power unit watts) is provided for different seal areas, the LS-TS, SA areas. The SA area indicates the LS edge area to which a heat-sealable polymer strip is applied to provide liquid tightness inside the package for the filled liquid product, as shown in Figure 7a.

[0192] From the results in (Table 3), it can be seen that only Sample 2 provides a power window for induction heat sealing in the transverse seal operation, and that window is also quite wide. Furthermore, the packaging material of Sample 2 provides a wider window for both LS and SA high-frequency induction heat sealing compared to the comparative samples.

[0193] Furthermore, regarding the attached drawings: Figure 1 shows in cross-section an embodiment of a barrier-coated cellulose-based substrate 10 manufactured by the method of the present invention. The cellulose-based substrate 11 has a density exceeding 900 kg / m 3 and a basis weight of about 40 g / m 2 , an upper surface roughness Bentsen value of less than 30 ml / min, and a cob 60 value of 25 g / m 2Paper that is less than, coated in the form of an aqueous wet coating composition, and then heat-dried at 60°C to 95°C so that moisture evaporates from the applied wet coating, with a base coating 12 made of starch such as Avebe's Etenia® applied. The starch is applied as two consecutive wet coatings with intermediate drying, each about 0.5 g / m 2 It was. The total dry weight of the obtained starch base coating is about 1 g / m 2 It is. Furthermore, the cellulose-based substrate thus base-coated is vapor-coated with an aluminum metallization coating 13, i.e., an aluminum metallization layer, applied by physical vapor deposition on the dry surface of the base coating 12 and vapor-deposited until the sheet resistance reaches 0.5 ohm / square.

[0194] The paper substrate thus metallized and base-coated has a further heat-resistant gas barrier top coating 14 of an aqueous solution of Kuraray's PVOH, Poval® 6-98, applied on the surface of the aluminum coating 13. The heat-resistant gas barrier top coating 14 is applied and dried in the same manner as the base coating, and the dry weight of the top coating of the PVOH gas barrier composition is about 0.7 g / m 2This is the case. Since the top coating of the gas barrier PVOH composition is sensitive to moisture, dirt, and liquids, if necessary, at least an additional layer or coating 15 of a protective polymer is applied onto the top coating layer 14 of PVOH. The additional layer or coating 15 may be a thermoplastic polymer such as a polyolefin, for example LPDE, or an ethylene-based adhesive polymer, for example EAA, or a maleic anhydride graft copolymer with polyethylene. Such an additional polyolefin layer is usually necessary for measuring the oxygen transmission rate of the barrier-coated cellulosic substrate and covers defects such as pinholes in the first PVOH coating. If the additional protective coating 15 is made of a thermoplastic polymer or material, the laminate structure 10 is itself also a heat-sealable barrier packaging material or packaging material. The additional polymer layer or additional coating itself has no inherent oxygen barrier properties or has very low ones and thus does not further contribute to the measured oxygen transmission rate value. An additional layer or coating 16 of a protective polymer of the same type or a different type as the coating or layer 15 may be applied, if necessary, also on the opposite side of the cellulosic substrate. As a result, a simple laminate material 10 can be obtained by simply adding the outermost protective polymer layers 15 and 16 to the barrier-coated cellulosic substrate.

[0195] Figure 2 shows a laminate packaging material 20 for packaging oxygen-sensitive products, for example for liquid carton packaging, which packaging material comprises the barrier-coated cellulosic substrate 10;25 of the present invention. This laminate material has a bending force of 80 mN and about 200 g / m 2It further includes a bulk layer 21 of paperboard having a basis weight, and further includes an outermost protective layer, for example, a liquid-tight and heat-sealable polymer layer 22 applied outside the bulk layer 21, and this layer 22 is directed toward the outside of the packaging container manufactured from the packaging laminate. The layer 22 is transparent in order to show the printed decorative pattern 27 printed on the bulk layer of paper or paperboard to the outside. Thereby, the printed pattern can inform the contents of the package, the packaging brand, and other information targeted at consumers in retail stores and grocery stores. The polymer of the outermost layer 22 may be a polyolefin such as a conventional low-density polyethylene (LDPE) with heat-sealable quality, but may also include further similar polymers including LLDPE. The coating amount is about 12 g / m 2 is.

[0196] The innermost liquid-tight and heat-sealable general-purpose layer 23 may be disposed on the opposite side of the bulk layer 21 directed toward the inside of the packaging container manufactured from the packaging laminate. That is, the layer 23 is in direct contact with the packaged product. Thus, the innermost heat-sealable general-purpose layer 23 that forms a strong lateral heat seal of the liquid packaging container manufactured from the laminate packaging material may include one or more combinations of polyethylene selected from the group consisting of LDPE, linear low-density polyethylene (LLDPE), and LLDPE manufactured by polymerizing ethylene monomer with C4-C8, for example, C6-C8 alpha-olefin alkylene monomer in the presence of a metallocene catalyst, that is, so-called metallocene-LLDPE (m-LLDPE). The innermost liquid-tight and heat-sealable general-purpose layer 23 can be applied in an amount of 20 to 35 g / m 2 can be applied in an amount of.

[0197] According to a preferred embodiment, the innermost heat-sealable and liquid-tight layer includes a pre-manufactured oriented film 23a and includes at least one sublayer whose main component is linear low-density polyethylene (LLDPE). The film may further contain some LDPE. The thickness of the oriented film 23a is 12 to 25 μm, for example 15 to 20 μm, for example 18 μm.

[0198] The pre-fabricated oriented film 23a is laminated to the surface of the PVOH 14 top coating of the barrier-coated paper substrate 25 by means of an intermediate melt-extruded laminating adhesive layer portion 28 comprising a 5-8 μm tie layer of EAA and / or a further adhesive layer 23b of melt-extrusion laminated LDPE to a thickness of 12-20 μm, e.g., 12-18 μm.

[0199] The innermost heat seal layer 23 is made up of two or more coextruded partial layers (23a) of the same or different blends of LDPE and m-LLDPE. * , 23b * These layers may be applied to the surface of the thermally stable gas barrier top coating 14 of the barrier coated paper substrate 25; 10 at a rate of several g / m 2 , for example, 4 to 7 g / m 2 , and an intermediate bonding layer 28, also coextruded. * 10, by applying the layers together in a single melt co-extrusion coating step.

[0200] The bulk layer 21 is laminated to the uncoated side of the barrier-coated paper substrate 25 (10 in Figure 1) by an intermediate bonding layer 26 of low-density polyethylene (LDPE). The intermediate bonding layer 26 is formed by melt extrusion as a thin polymer melt curtain between the two paper webs, and the bulk layer and the barrier-coated paper substrate are laminated together when all three layers pass through a chilled press roller nip. The thickness of the intermediate bonding layer 26 is 12-18 mm, for example 12-15 mm.

[0201] In another embodiment, the bulk layer 21 is provided with an intermediate adhesive layer 26, a thin layer of adhesive polymer obtained by applying an aqueous dispersion of polyvinyl acetate adhesive to one of the surfaces to be bonded together, followed by pressing them together in a roller nip. *It is laminated to the barrier-coated paper substrate 25 by wet lamination with. Such a lamination step does not require a drying operation that consumes the energy necessary to accelerate the evaporation of water, and is carried out in an efficient cold or normal-temperature lamination step at an industrial speed. Intermediate adhesive layer 26 * The applied dry amount of is only 3 to 4 g / m 2 and there is no need for drying and evaporation.

[0202] Therefore, in this laminate layer, the amount of the thermoplastic polymer can be significantly reduced as compared with the conventional polyethylene melt extrusion laminate adhesive layer 26 described above in relation to FIG. 2.

[0203] FIG. 3a shows the process of the aqueous dispersion coating 30a, which can be used to apply the aqueous compositions of the gas barrier polymer coating layers 12 and 14. The paper substrate web 31a (for example, the cellulose-based substrate 11 of FIG. 1) is sent to a dispersion coating station 32a, where the aqueous composition is applied to the upper surface of the substrate by a roller. When the surfaces on both sides of the substrate are different, usually there is one surface that is more suitable for receiving a coated or printed decorative pattern, and thus this is the surface to be coated in the present invention (this surface is called the upper surface or the printed surface). Since the aqueous content of the composition is 80 to 99% by weight, there is a large amount of water on the wet-coated substrate, and it is necessary to dry and evaporate this water to form a continuous coating having homogeneous and uniform quality with respect to the barrier properties and surface properties, that is, low uniformity and low occurrence of defects. Drying is performed by a hot air dryer 33a, whereby the moisture evaporates and is removed from the surface of the substrate. The surface temperature when the substrate passes through the dryer is consistently maintained at a temperature below 95°C, for example 60 to 95°C, for example 70 to 90°C, for example below 80 to 90°C, for example below about 85°C.

[0204] The resulting gas barrier coated paper substrate web 34a is sent for cooling and wound onto reels for intermediate storage. Optionally, at a next or later stage, the thus coated web may be sent to a further coating step, such as physical vapor deposition coating of a barrier vapor coating 13 onto the base coated paper substrate 11-12.

[0205] FIG. 3b shows the final lamination process step in the manufacture of the packaging laminate 20 of FIG. 2 after the bulk layer 21 has first been laminated (i.e., 25) to the barrier-coated cellulosic substrate 10 of FIG. 1.

[0206] As described in connection with Figure 2, the bulk layer paperboard 21 may be laminated to the barrier-coated paper substrate 10, 25 by wet, cold, aqueous adhesive lamination or melt extrusion lamination. The wet lamination adhesive may be applied as described in connection with dispersion coating in Figure 3a, and lamination is accomplished by simply pressing the surfaces to be joined together without forcing the adhesive composition to dry. The primary method of melt extrusion lamination is shown in Figure 3b, as described below.

[0207] The resulting pre-laminated web 31b of paper is fed directly from an intermediate storage reel or from a lamination station for laminating a pre-lamination of the bulk layer to a cellulose substrate coated with a barrier coating. The unlaminated side of the bulk layer 21, i.e., the printing side, is melt extrusion coated by being joined to a molten polymer curtain 32 of LDPE that forms the outermost layer 22 of the laminate material by a cooling roller nip 33. The LDPE is extruded from an extruder feed block and die 32b and forms the outermost layer 22 of the laminated material. Thereafter, the outermost layer 22, i.e., the pre-laminated bulk paper web coated on the outside, passes through a second extruder feed block and die 34b and a lamination nip 35, where a molten polymer curtain 34 is joined to and coated on the other side of the pre-lamination, i.e., the barrier coating side of the paper substrate 10;25. In this way, the innermost heat-sealable layer 23a and any intervening polymer layer 23b are optionally co-extrusion coated inside the paper pre-laminated web together with a tie layer of an adhesive polymer having functional groups for enhancing the adhesion to adjacent layers, and the finished laminated packaging material 20;36 is formed and finally wound onto a storage reel (not shown).

[0208] These two co-extrusion steps at the lamination roller nips 33 and 35 may alternatively be carried out as two consecutive steps in the reverse order.

[0209] According to another embodiment, one or both of the outermost layers may alternatively be applied at separate pre-lamination stations, in which case the co-extrusion coating layer is first applied outside the (printed) bulk paperboard layer and inside the barrier-coated paper substrate, and finally, then the two pre-laminated paper webs may be laminated to each other by extrusion lamination or wet lamination as described above.

[0210] According to a preferred embodiment, the innermost layer of the heat-sealable and liquid-tight thermoplastic resin layer is applied in the form of a pre-manufactured polymer film 23a, which is laminated to the coated surface of the barrier-coated paper substrate 10; 25.

[0211] The pre-manufactured film for the innermost layer 23a is laminated to the barrier-coated paper substrate 10; 25 by melt extrusion lamination (the melt-extruded intermediate layer 23b * and / or 28), or alternatively, by wet normal-temperature aqueous adhesive lamination with an intermediate layer of the adhesive polymer 28 * may be laminated.

[0212] FIG. 4 is a perspective view showing an example of a physical vapor deposition (PVD) plant, such as an aluminum metal film, on the web substrate of the present invention. The base-coated paper substrate 44 is passed through the deposition chamber, and in the deposition chamber, on the base-coated side, it is subjected to continuous deposition 40 of evaporated aluminum, and a metallized layer of aluminum is formed. The coating is performed with a thickness of 5 to  100 nm, for example, 10 to 80 nm, preferably 10 to 50 nm, to form the barrier-coated paper 43 of the present invention. The aluminum vapor is formed from ion bombardment of the evaporation source of the solid piece of aluminum 41.

[0213] Figure 5a shows an embodiment of a packaging container 50a manufactured from a packaging laminate according to the present invention. The packaging container is particularly suitable for beverages, sauces, soups, etc. Usually, the capacity of such a package is about 100 to 1000 ml. The package can be of any shape, but is preferably brick-shaped, having longitudinal and transverse seals 51a and 52a respectively, and optionally an opening device 53. In another embodiment not shown, the packaging container may be wedge-shaped. To obtain such a "wedge shape", only the bottom of the package is bent to form, and the horizontal heat seal at the bottom is hidden under the triangular corner flap that is bent and sealed against the bottom of the package. The upper horizontal seal remains unbent. In this way, the partially folded packaging container is easy to handle and has sufficient dimensional stability to be placed on the shelves of grocery stores or any flat surface.

[0214] Figure 5b shows an alternative of a packaging container 50b manufactured from an alternative packaging laminate according to the present invention. This alternative packaging laminate is thinner by having a thinner paper bulk layer, and thus does not have sufficient dimensional stability to form a parallelepiped or wedge-shaped packaging container, and no crease is formed after the transverse seal 52b. The packaging container remains in the form of a pillow-shaped pouch and is distributed and sold in this form.

[0215] Figure 5c shows a gable-top package 50c, which is formed by folding from a pre-cut sheet or blank made of a laminate packaging material including a paper bulk layer of cardboard and the barrier-coated paper substrate of the present invention. Also, a flat-top package may be formed from a similar blank material.

[0216] Figure 5d shows a bottle-shaped package 50d that combines a sleeve 54 formed from a pre-cut blank of the laminate packaging material of the present invention and a top 55 formed by injection molding plastic in combination with an opening device such as a screw cork. This type of package is sold, for example, under the trade names Tetra Top® and Tetra Evero®. These particular packages are formed by attaching a molded top 55, with the opening device in a closed state, to a tubular sleeve 54 of laminate packaging material, sterilizing the resulting bottle top capsule, filling it with food, and finally folding and shaping the bottom of the package and sealing it.

[0217] Figure 6 illustrates the principle described in the preamble of the present application, namely, by overlapping and thermally sealing the longitudinal edges 62, 62' of the web to each other to form an overlap joint 63, the web of packaging material is formed into a tube 61. The tube is continuously filled with the liquid food to be filled (64) and is divided into individual filled packages by repeatedly making double transverse seals 65 of the tube at a predetermined interval below the level of the filled contents in the tube. The packages 66 are separated by cutting between the double transverse seals (upper seal and lower seal) and are finally formed into the desired geometric configuration by folding along the fold lines provided in the material.

[0218] Finally, it should be noted that the present invention is not limited by the embodiments shown and described above, and various modifications are possible within the scope described in the claims.

Claims

1. A barrier-coated cellulosic substrate (10) for use as a barrier sheet of a heat-sealable laminate packaging material for oxygen-sensitive products, comprising a cellulosic substrate (11), a base coating (12) containing 60 wt% or more of a material selected from the group consisting of starch, modified starch materials, and cellulose ethers, said base coating being applied by dispersion or solution coating and then dried onto the surface of the first side of the cellulosic substrate to provide a smooth and heat-resistant mechanical base coating, a metallized coating (13) applied onto the free surface of said base coating, said metallized coating being applied onto the base coating by vapor deposition, and said barrier-coated cellulose-based substrate (10) further comprising a heat-resistant gas barrier top coating (14), said gas barrier top coating being applied by dispersion or solution coating onto said metallized coating (13) and then dried, said heat-resistant gas barrier top coating (14) being further coated or laminated with a heat-sealable layer (15) of a thermoplastic material, said heat-resistant gas barrier top coating having a melting temperature higher than that of said heat-sealable layer of the thermoplastic material, said barrier-coated cellulose-based substrate providing good gas barrier properties and enabling robust induction heat-sealing conditions in a laminate packaging material for manufacturing packages. Barrier-coated cellulosic substrate (10).

2. The barrier-coated cellulosic substrate according to claim 1, wherein said base coating (12) contains 70 wt% or more, for example 80 wt% or more, for example 90 wt% or more of a material selected from the group consisting of starch, modified starch materials, and cellulose ethers. The barrier-coated cellulosic substrate according to claim 1.

3. The base coating (12) is applied in an amount of 0.5 to 2 g / m ２ , preferably 0.5 to 1.5 g / m ２ in terms of dry weight, The barrier-coated cellulosic substrate according to claim 1 or 2.

4. The base coating (12) is applied in two successive coatings with intermediate drying, each in an amount of 0.2 to 0.8 g / m ２ , for example, 0.5 to 0.7 g / m ２ by dry weight. The barrier-coated cellulosic substrate according to any one of claims 1 to 3.

5. The barrier-coated cellulosic substrate according to any one of claims 1 to 4, wherein said base coating (12) further contains an inorganic particle or filler in an amount such as 1 to 30 wt%. The barrier-coated cellulosic substrate according to any one of claims 1 to 4.

6. The metallization coating (13) is a vapor deposition coating of a metal such as an aluminum coating. The barrier-coated cellulose-based substrate according to any one of claims 1 to 5.

7. The metallization coating (13) is applied by physical vapor deposition to a sheet resistance value of 0.25 to 0.75 Ω□, for example, 0.4 to 0.6 Ω□. The barrier-coated cellulose-based substrate according to any one of claims 1 to 6.

8. The heat-resistant gas barrier top coating (14) includes a polymer selected from the group consisting of vinyl alcohol polymers and copolymers, such as polyvinyl alcohol (PVOH), ethylene vinyl alcohol (EVOH), modified vinyl alcohol polymers and copolymers, such as modified PVOH and modified EVOH, and blends consisting mostly of such polymers. The barrier-coated cellulose-based substrate according to any one of claims 1 to 7.

9. The heat-resistant gas barrier top coating (14) further includes a copolymer (EMAA) of ethylene and acrylic acid (EAA) or methacrylic acid. The barrier-coated cellulose-based substrate according to any one of claims 1 to 8.

10. The heat-resistant gas barrier top coat (14) is applied in an amount of 0.5 to 2 g / m by dry weight ２ , preferably 0.5 to 1.5 g / m ２ by dry weight The barrier-coated cellulose-based substrate according to any one of claims 1 to 9.

11. The heat-resistant gas barrier top coating (14) is applied in an amount of 0.2 to 1.5 g / m, ２ for example, 0.2 to 1 g / m, ２ for example, 0.5 to 0.8 g / m, ２ by two consecutive coatings with intermediate drying, The barrier-coated cellulose-based substrate according to any one of claims 1 to 10.

12. The base material is paper having a weight of 30 to 70 g / m measured in accordance with ISO 536:2012 ２ and a density of 800 to 1400 kg / m measured in accordance with ISO 534:2011 ３ is paper having a density of The barrier-coated cellulose-based substrate according to any one of claims 1 to 11.

13. A method for manufacturing a barrier-coated cellulose-based substrate (10) for use in a heat-sealable laminate packaging material for packaging oxygen-sensitive products, comprising: a) conveying a cellulose-based substrate (11; 31a); b) providing an aqueous-based coating composition containing 60% by weight or more, based on dry weight, of a material selected from the group consisting of starch, modified starch materials, and cellulose ethers; c) applying the aqueous-based coating composition to the upper surface of the web of the cellulose-based substrate by a dispersion coating (32a) such as a roll coating method. d) drying the aqueous gas barrier polymer coating applied in step c) (33a) to provide a smooth base coating layer (12); e) optionally, repeating step c) and step d); f) vapor deposition coating (40) and metallizing the base-coated and dried web substrate obtained in step e) to form a metallized coating (13); g) applying an aqueous solution or dispersion (32a) of a heat-resistant gas barrier topcoat material onto the metallized coating by a roll coating method or the like; h) drying the aqueous solution or dispersion applied in step g) (33a) to obtain a heat-resistant gas barrier topcoat (14); i) optionally, repeating step g) and step h); j) obtaining a barrier-coated cellulose-based substrate with defects in the base coating, the gas barrier topcoat, and the metallized coating minimized; k) further coating the surface of the heat-resistant gas barrier topcoat with a heat-sealable layer (15) of a thermoplastic material, wherein the heat-resistant gas barrier topcoat layer has a melting temperature higher than that of the heat-sealable layer of the thermoplastic material; Method. **Claim 14** The method according to claim 13, wherein the heat-resistant gas barrier topcoat (14) comprises a polymer selected from vinyl alcohol polymers and copolymers, such as polyvinyl alcohol (PVOH), ethylene vinyl alcohol (EVOH), modified vinyl alcohol polymers and copolymers, such as modified PVOH and modified EVOH, and blends predominantly comprising such polymers. The method according to claim 13. **Claim 15** A barrier-coated cellulosic substrate (10; 25) according to any one of claims 1 to 12, further comprising a first outermost protective material layer (22) and a second innermost liquid-tight and heat-sealable material layer (23; 23a; 23a ＊ ) A laminate packaging material (20). **Claim 16** A barrier-coated cellulosic substrate (10; 25) according to any one of claims 1 to 12, comprising a first outermost liquid-tight and heat-sealable polyolefin layer (22) and a second innermost liquid-tight and heat-sealable polyolefin layer (23; 23a; 23a ＊ ) further comprising A laminate packaging material (20). **Claim 17** A bulk layer (21) of paper or cardboard or other cellulosic material, disposed inside the bulk layer, between the bulk layer and a second innermost liquid-tight and heat-sealable material layer or polyolefin layer (23; 23a; 23a ＊ ) and further comprising a barrier-coated cellulosic substrate (10; 25) disposed therebetween The laminate packaging material (20) according to claim 15 or 16. **Claim 18** The barrier-coated cellulose-based substrate (10; 25) is bonded to the bulk layer (21) by an intermediate bonding layer (26) comprising a composition containing a binder selected from the group consisting of acrylic polymers and copolymers, starch, starch derivatives, cellulose and polysaccharide derivatives, polymers and copolymers of vinyl acetate and / or vinyl alcohol, and copolymers of styrene-acrylic latex or styrene-butadiene latex. The laminated packaging material (20) according to claim 17. **Claim 19** The second innermost liquid-tight and heat-sealable material layer (23) is a pre-manufactured polyolefin film (23a), for example, an oriented polyethylene film containing at least one layer predominantly occupied by an LLDPE polymer, in order to improve the robustness of the mechanical properties of the laminated packaging material. The laminated packaging material (20) according to any one of claims 15 to 18. **Claim 20** A packaging container (50a; 50b; 50c; 50d) comprising the laminated packaging material according to any one of claims 15 to 19.

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