Method for producing coated paper or paperboard products

Abstract

The present invention relates to a method for producing a coated paper or paperboard product, the method comprising the steps of: a) providing a coated paper or paperboard product having a viscosity of at least 100 g / m2, determined in accordance with ISO 638; 2 Weighing capacity: 900 kg / m 3 a) providing a paper or paperboard substrate having a density of less than 1000 nm and a moisture content of at least 3.5% by weight, the paper or paperboard substrate having a first major surface and a second major surface; b) forming a first water vapor barrier layer on the first major surface of the paper or paperboard substrate, the first water vapor barrier layer comprising a thermoplastic polymer; c) forming a second water vapor barrier layer on the second major surface of the paper or paperboard substrate, the second water vapor barrier layer comprising a thermoplastic polymer; and d) forming a vacuum coating layer on the first water vapor barrier layer to obtain a coated paper or paperboard product.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates to coated paper or paperboard products that include a vacuum coating layer, and methods for making the same. [Background technology]

[0002] Coating paper and paperboard with plastics is often used to combine the mechanical properties of paper or paperboard with the barrier and sealing properties of plastic films. Adding a suitable plastic material to paper or paperboard, even in relatively small amounts, can provide the properties necessary to make the paper or paperboard suitable for many demanding applications, such as liquid or food packaging boards. In boards for liquid or food packaging, polyolefin coatings are frequently used as liquid barrier layers, heat-sealing layers, and adhesives. However, recycling such polymer-coated boards is difficult because it is difficult to separate the polymer from the fibers.

[0003] Furthermore, in many cases, the water vapor barrier properties of polymer-coated paper or paperboard remain insufficient unless the coating layer is thick or a combination of different polymer coating layers is used. Therefore, to ensure high water vapor barrier properties, polymer-coated paper or paperboard is often combined with one or more layers of aluminum foil. However, adding polymer and aluminum foil significantly increases costs, and the combination of the polymer coating layer and aluminum foil makes the material more difficult to recycle. Furthermore, due to the large carbon footprint, there is a desire to replace aluminum foil in paper and paperboard-based packaging materials with renewable materials.

[0004] Aseptic packaging for shelf-stable products such as milk and juice is typically made from liquid or food packaging cardboard containing a multi-layer paperboard base substrate, an outermost layer of heat-sealable polyolefin (e.g., polyethylene, PE), and an innermost layer of polyolefin and aluminum. The aluminum foil layers required to provide water vapor and oxygen barrier properties are typically incorporated between the polyethylene layers, giving a PE / paperboard / PE / aluminum / PE structure.

[0005] Attempts have been made in the prior art to replace aluminium foil with more environmentally friendly and / or easier to recycle solutions, but so far without any real success.

[0006] One solution proposed in the prior art is to apply very thin organic or inorganic barrier coating layers using vacuum deposition techniques such as physical vapor deposition (PVD) or chemical vapor deposition (CVD). Vacuum-deposited barrier coating layers can include or consist of, for example, AlOx, Al2O3, or SiOx. These very thin coating layers typically have thicknesses in the range of 20 to 600 nm, more preferably 50 to 250 nm, and when applied to an appropriate substrate, can provide good oxygen and water vapor barrier properties comparable to those of thick aluminum foil. The thickness of vacuum-deposited coatings is typically at least an order of magnitude thinner than conventional foils, allowing for significant reductions in the metal content of the product.

[0007] However, so-called direct vacuum coating, or direct metallization, in which a vacuum-deposited coating is applied directly to the paper or paperboard substrate to be coated, has proven problematic, especially for thick paper or paperboard grades. The coating process is carried out under vacuum, which means that the paper or paperboard substrate must be degassed. In addition to increasing costs, degassing means that the substrate must be dried to a very low moisture content. This drying and subsequent re-moistening to ambient moisture levels alters the mechanical properties of the paper or paperboard substrate. Not only does drying increase the paper or paperboard substrate's tendency to crack and its post-processing stability, but there is also a significant risk of cracking the thin, delicate vacuum coating layer when the substrate is re-moistened. Some additives commonly used in paper or paperboard are volatile and can migrate, thus potentially causing deposits in the vacuum coating machine.

[0008] A solution proposed in the prior art is to first provide a vacuum coating layer on a thin substrate in the form of a plastic film or on a high density or compressed paper, and then laminate the vacuum coated substrate to a base layer of paper or paperboard, thereby providing the base layer with improved barrier properties. However, this lamination type solution increases the cost and complexity of the manufacturing process.

[0009] Thus, there remains a need for improved solutions to replace the combination of plastic film and aluminum foil in paper and paperboard based packaging materials while maintaining acceptable liquid, water vapor, and oxygen barrier properties. At the same time, there is a need to replace the combination of plastic film and aluminum foil with alternatives that facilitate the repulping and recycling of post-consumer packaging materials. Summary of the Invention

[0010] An object of the present disclosure is to provide an alternative to the combination of plastic film and aluminum foil that is commonly used as a barrier layer to provide water vapor barrier properties to packaging materials such as boards for liquid or food packaging.

[0011] It is a further object of the present disclosure to provide a method by which a vacuum deposited coating can be performed directly on the paper or paperboard substrate to be coated, rather than first applying a vacuum coating layer to a thin substrate.

[0012] A further object of the present disclosure is to provide a method for treating a pulmonary artery disease (PA) comprising administering to a patient a pulmonary artery disease (PADA) having a PADA of 10 cc / m 2 or less, as measured in accordance with ASTM standard F1927 at 50% relative humidity and 23°C. 2 The objective is to provide a barrier layer having an oxygen transmission rate (OTR) of less than 1 / 24h.

[0013] A further object of the present disclosure is to provide a method for producing a cellulose ester having a viscosity of 10 g / m 2 as measured in accordance with ASTM standard F1249 at 50% relative humidity and 23°C. 2 The objective of the present invention is to provide a barrier layer having a water vapor transmission rate (WVTR) of less than 1 / 24h.

[0014] It is a further object of the present disclosure to provide a coated paper or paperboard product useful as, for example, a board for packaging liquids or food products, which facilitates repulping and recycling of the packaging board compared to conventional packaging laminates using a combination of plastic film and aluminum foil.

[0015] The above objectives, as well as other objectives which will be realized by those skilled in the art in light of this disclosure, are achieved by various aspects of the present disclosure.

[0016] Direct vacuum coating, or direct metallization, in which a vacuum-deposited coating is applied directly to the paper or paperboard substrate to be coated, has proven problematic, especially for thick paper or paperboard grades. The coating process is carried out under vacuum, which means that the paper or paperboard substrate must be degassed. In addition to increasing costs, degassing means that the substrate must be dried to a very low moisture content. This drying and subsequent re-moistening to ambient moisture levels alters the mechanical properties of the paper or paperboard substrate. Not only does drying increase the paper or paperboard substrate's tendency to crack and its post-processing stability, but there is also a significant risk of cracking the thin, delicate vacuum coating layer when the substrate is re-moistened. Some additives commonly used in paper or paperboard are volatile and can migrate, thus potentially causing deposits in the vacuum coating machine.

[0017] The present invention solves this problem by sealing each major surface of the paper or paperboard substrate with a water vapor barrier layer so that the moisture content of the paper or paperboard substrate is retained within the substrate when the vacuum coating process is performed. DETAILED DESCRIPTION OF THE INVENTION

[0018] According to a first aspect described herein, there is provided a method of producing a coated paper or paperboard product, the method comprising: a) At least 100 g / m2, determined in accordance with ISO 638 2 Weighing capacity: 900 kg / m 3 providing a paper or paperboard substrate having a density of less than 1000 .mu.m and a moisture content of at least 3.5% by weight, said paper or paperboard substrate having a first major surface and a second major surface; b) forming a first water vapor barrier layer on a first major surface of a paper or paperboard substrate, said first water vapor barrier layer comprising a thermoplastic polymer; c) forming a second water vapor barrier layer on a second major surface of the paper or paperboard substrate, the second water vapor barrier layer comprising a thermoplastic polymer; and d) forming a vacuum coating layer on the first water vapor barrier layer to obtain a coated paper or paperboard product. Including, Step (d) of forming a vacuum coating layer on the first water vapor barrier layer is performed after step (b) of forming a first water vapor barrier layer on the first major surface of the paper or paperboard substrate and after step (c) of forming a second water vapor barrier layer on the second major surface of the paper or paperboard substrate.

[0019] A paper or paperboard substrate (also referred to herein as "substrate") is a sheet or web-like material formed primarily from wood pulp or other fibrous material. A paper or paperboard substrate has a first major surface and a second major surface.

[0020] The method of the present disclosure is particularly useful for heavier paper or paperboard grades having a moisture content of at least 3.5% by weight. Accordingly, the paper or paperboard substrate used in the method should have a moisture content of at least 100 g / m2, as determined in accordance with ISO 638. 2 Weighing capacity: 900 kg / m 3 It should have a density of less than 1000 and a moisture content of at least 3.5% by weight.

[0021] In some embodiments, the paper or paperboard substrate has a dry weight of 115 to 600 g / m 2 in the range of 150 to 450 g / m 2 Unless otherwise specified, the basis weight is determined in accordance with ISO standard 536.

[0022] In some embodiments, the paper or paperboard substrate has a dry weight of 350 to 900 kg / m 3 in the range of 450 to 850 kg / m 3 Unless otherwise specified, density is determined in accordance with ISO standard 534.

[0023] Due to the combination of basis weight and density, paper or paperboard substrates typically have a relatively high bending resistance, hi some embodiments, the paper or paperboard substrate has a geometric mean bending resistance of greater than 150 mN, preferably greater than 170 mN, more preferably greater than 190 mN, measured according to ISO 2493 (L&W, 15°).

[0024] Paper generally refers to a material made from wood pulp or other fibrous substances containing cellulose fibers in sheets or rolls and used for writing, drawing, or printing, or as a packaging material. Paper can be made either bleached or unbleached and in a variety of thicknesses, depending on the end-use requirements.

[0025] Paperboard generally refers to a strong, thick paper or cardboard containing cellulose fibers that is used, for example, as a flat substrate, tray, box, and / or other type of packaging. Paperboard can be produced in a variety of thicknesses, either bleached or unbleached, depending on the end-use requirements.

[0026] In some embodiments, the paper or paperboard substrate is a multi-ply paperboard. Multi-ply paper or paperboard substrates are preferably composed of two or more, more preferably three or more, cellulose-based plies. Each cellulose-based ply can have a particular pulp fiber composition, such as bleached and / or unbleached kraft pulp, sulfite pulp, dissolving pulp, thermomechanical pulp (TMP), chemi-thermomechanical pulp (CTMP), high-temperature CTMP (HT-CTMP), broke, and / or mixtures thereof. Different plies can have different basis weights and / or thicknesses and may contain different amounts of additives, such as internal sizing agents.

[0027] As an example, a paper or paperboard substrate may be constructed from one top ply of bleached and / or unbleached kraft pulp, a middle ply of a blend of bleached or unbleached kraft pulp and CTMP, and a bottom ply of bleached or unbleached kraft pulp, the middle ply having a greater caliper and / or lower density than both the top and bottom plies, respectively. In some embodiments, the middle ply has a caliper of 750 kg / m 3 less than 700 kg / m 3 less than 675 kg / m 3 The top and bottom plies have a density of less than 750 kg / m 3 More than 900 kg / m 3 In some embodiments, the paper or paperboard substrate comprises foamed paperboard. In some embodiments, at least one ply, preferably the middle ply, of the multi-ply paperboard substrate is foamed.

[0028] The paper or paperboard substrate may be surface sized or impregnated. In some embodiments, the paper or paperboard substrate is surface sized or impregnated on one or both sides with a surface sizing composition, preferably comprising a starch derivative, a cellulose derivative, or polyvinyl alcohol (PVOH), or a combination thereof. The starch derivative may be a slightly modified starch, e.g., oxidized or cationized. The cellulose derivative may be sodium carboxymethylcellulose having a degree of substitution greater than 0.4, e.g., in the range of 0.5 to 1.5. The PVOH may be fully or partially hydrolyzed. The surface sizing or impregnation may facilitate the release of the water vapor barrier layer from the paper or paperboard substrate during repulping. In some embodiments, the basis weight of the surface sizing composition is 0.2 to 10 g / m per side on a dry weight basis. 2 , preferably 0.4 to 8 g / m 2 , more preferably 0.8 to 5 g / m 2 is.

[0029] The paper or paperboard substrate provided in step a) has a moisture content of at least 3.5% by weight, determined according to ISO 638. This moisture content is typically suitable for further conversion into a paper or paperboard product, for example by folding or forming the paper or paperboard substrate. In some embodiments, the paper or paperboard substrate has a moisture content, determined according to ISO 638, in the range of 3.5 to 9% by weight, preferably in the range of 4 to 8% by weight.

[0030] The method of the present disclosure is particularly useful for paper or paperboard substrates that contain a hydrophobic internal size, as some of the hydrophobic internal size may be volatile and may migrate and cause deposits in vacuum coating machines. In some embodiments, the paper or paperboard substrate preferably contains a hydrophobic internal size selected from the group consisting of alkyl ketene dimer (AKD), alkenyl succinic anhydride (ASA), rosin size, fatty acid, fatty acid derivative, and combinations thereof. In some embodiments, the paper or paperboard substrate contains 0.1 to 10 kg / tn of hydrophobic internal size.

[0031] The paper or paperboard substrate itself, before the water vapor barrier layer is applied, will typically be highly permeable to water vapor. In some embodiments, the paper or paperboard substrate provided in step a) has a water vapor permeability of at least 100 g / m2, as measured according to ASTM standard F1249 at 50% relative humidity and 23°C. 2 / 24h, preferably at least 150g / m 2 / 24h, more preferably at least 200g / m 2 / 24h water vapor transmission rate (WVTR).

[0032] A coated paper or paperboard product is a material formed primarily from paper or paperboard that has been coated on one or both sides with at least one coating layer designed to improve the performance and / or appearance of the coated paper or paperboard product.

[0033] Coated paper or paperboard products typically have a first, outermost surface intended to serve as the exterior, or printing, surface, and a second, outermost surface intended to serve as the interior surface of a liquid or food packaging container. The surface of the coated paper or paperboard product that includes the vacuum coating layer is typically intended to face the inside of the liquid or food packaging container.

[0034] Coated paper or paperboard products according to the present invention can provide excellent oxygen barrier properties, water vapor barrier properties, and liquid barrier properties.

[0035] In the method of the present invention, a paper or paperboard substrate is first provided with a first water vapor barrier layer on a first major surface of the paper or paperboard substrate and a second water vapor barrier layer on a second major surface of the paper or paperboard substrate, and then a vacuum coating layer is formed on the first water vapor barrier layer to obtain a coated paper or paperboard product. In other words, step d) of the method of the present invention is performed after both steps b) and c) have been performed.

[0036] Sealing each major surface of the paper or paperboard substrate with a water vapor barrier layer helps maintain the moisture content within the paper or paperboard substrate when the vacuum coating process is performed.

[0037] A first moisture vapor barrier layer is formed on a first major surface of the paper or paperboard substrate. The first moisture vapor barrier layer comprises a thermoplastic polymer. In some embodiments, the thermoplastic polymer is a polyolefin or a blend of polyolefins, more preferably polyethylene, polypropylene, or a blend or copolymer thereof. In some embodiments, the thermoplastic polymer is polyethylene. In preferred embodiments, the thermoplastic polymer is low density polyethylene (LDPE) or linear low density polyethylene (LLDPE).

[0038] In some embodiments, the first water vapor barrier layer is formed by dispersion coating using a dispersion containing a thermoplastic polymer. Dispersion coating is a liquid film coating process in which a dispersion containing a thermoplastic polymer is applied to a substrate to form a thin, uniform layer and then dried. The liquid phase of the dispersion is preferably water or an aqueous solution, although organic solvents or mixtures of water or aqueous solutions with organic solvents can also be used. The thermoplastic polymer is present in the dispersion in the form of polymer particles, such as a latex. The dispersion can be applied by contact or non-contact coating methods. Examples of useful coating methods include, but are not limited to, rod coating, curtain coating, film press coating, cast coating, transfer coating, size press coating, flexographic coating, gate roll coating, twin-roll HSM coating, blade coating (e.g., short-time blade coating), jet applicator coating, spray coating, gravure coating, or reverse gravure coating.

[0039] In some embodiments, the first water vapor barrier layer is formed by extrusion coating of a thermoplastic polymer or dispersion coating of a dispersion containing a thermoplastic polymer. In some embodiments, the first water vapor barrier layer is formed by extrusion coating of a thermoplastic polymer, preferably a polyolefin or a blend of polyolefins, more preferably polyethylene, polypropylene, or a blend or copolymer thereof. In preferred embodiments, the thermoplastic polymer is low density polyethylene (LDPE) or linear low density polyethylene (LLDPE).

[0040] In some embodiments, the thermoplastic polymer has a melting point in the range of 90 to 120°C, preferably in the range of 100 to 110°C.

[0041] In some embodiments, the first water vapor barrier layer has a thickness of 6 to 25 g / m 2 in the range of 8 to 20 g / m 2The weight ranges from 1000 to 10 ...

[0042] By forming a first water vapor barrier layer on the first major surface of the paper or paperboard substrate, the melting point of the thermoplastic polymer can be relatively low, and the basis weight of the layer can also be reduced. Specifically, the melting point and basis weight of the thermoplastic polymer can be low compared to the melting point and basis weight of the thermoplastic polymer of the plastic film, in which case the plastic film is first provided with a vacuum coating layer and then laminated to the base layer of the paper or paperboard. The low melting point of the thermoplastic polymer and the low basis weight of the first water vapor barrier layer facilitate repulping and recycling of the paper or paperboard product.

[0043] To minimize the risk of pinholes, the water vapor barrier layer is preferably applied in at least two distinct coating steps, with the coating layer being dried or hardened between each coating step.

[0044] A second water vapor barrier layer is formed on the second major surface of the paper or paperboard substrate. The second water vapor barrier layer comprises a thermoplastic polymer. The second water vapor barrier layer may be of the same type as the first water vapor barrier layer or a different type.

[0045] In some embodiments, the second water vapor barrier layer is formed by extrusion coating of a thermoplastic polymer or dispersion coating of a dispersion containing a thermoplastic polymer. In some embodiments, the thermoplastic polymer is a polyolefin or a blend of polyolefins, more preferably polyethylene, polypropylene, or a blend or copolymer thereof. In preferred embodiments, the thermoplastic polymer is low-density polyethylene (LDPE) or linear low-density polyethylene (LLDPE).

[0046] In some embodiments, the second water vapor barrier layer is formed by dispersion coating using a dispersion containing a thermoplastic polymer. Dispersion coating is a liquid film coating process in which a dispersion containing a thermoplastic polymer is applied to a substrate to form a thin, uniform layer and then dried. The liquid phase of the dispersion is preferably water or an aqueous solution, although organic solvents or mixtures of water or aqueous solutions with organic solvents can also be used. The thermoplastic polymer is present in the dispersion in the form of polymer particles, such as a latex. The dispersion can be applied by contact or non-contact coating methods. Examples of useful coating methods include, but are not limited to, rod coating, curtain coating, film press coating, cast coating, transfer coating, size press coating, flexographic coating, gate roll coating, twin-roll HSM coating, blade coating (e.g., short-time blade coating), jet applicator coating, spray coating, gravure coating, or reverse gravure coating.

[0047] In some embodiments, the second water vapor barrier layer is formed by extrusion coating of a thermoplastic polymer or dispersion coating of a dispersion containing a thermoplastic polymer. In some embodiments, the second water vapor barrier layer is formed by extrusion coating of a thermoplastic polymer, preferably a polyolefin or a blend of polyolefins, more preferably polyethylene, polypropylene, or a blend or copolymer thereof. In preferred embodiments, the thermoplastic polymer is low-density polyethylene (LDPE) or linear low-density polyethylene (LLDPE).

[0048] In some embodiments, the thermoplastic polymer has a melting point in the range of 90 to 120°C, preferably in the range of 100 to 110°C.

[0049] In some embodiments, the second water vapor barrier layer has a thickness of 2 to 35 g / m 2 in the range of 2 to 25 g / m2 in the range of 4 to 20 g / m 2 To minimize the risk of pinholes, the water vapor barrier layer is preferably applied in at least two distinct coating steps, with the coating layer being dried or solidified between each coating step.

[0050] The layers applied to the paper or paperboard substrate in steps b) and c) are water vapor barrier layers. As used herein, the term water vapor barrier layer refers to a layer that prevents or significantly limits the passage of water vapor across the coated surface. More specifically, the first and second water vapor barrier layers each provide a water vapor transmission rate (WVTR) of the coated paper or paperboard substrate of 75 g / m or less, as measured according to ASTM standard F1249 at 50% relative humidity and 23°C. 2 / 24h less than 50g / m 2 / 24h or less, preferably 30g / m 2 / 24h.

[0051] The reduced WVTR caused by the first and second water vapor barrier layers significantly reduces the drying required or caused by subsequent vacuum coating processes.

[0052] The first and second water vapor barrier layers also function as liquid water barrier layers. In some embodiments, the first and second water vapor barrier layers each have a water vapor barrier strength of 50 g / m2 as measured according to ISO standard 535. 2 Less than Cobb 600 It has a value.

[0053] When the first and second water vapor barrier layers are formed on a paper or paperboard substrate, a vacuum coating layer is formed on the first water vapor barrier layer to obtain a coated paper or paperboard product.

[0054] Vacuum coating refers to a range of processes used to deposit layers of metals, metal oxides, and other inorganic and organic compositions onto solid surfaces, typically atom by atom or molecule by molecule. Multiple layers of the same or different materials can be combined. Processes can be further specified based on the vapor source: physical vapor deposition (PVD) uses liquid or solid sources, while chemical vapor deposition (CVD) uses chemical vapors.

[0055] Vacuum coating typically results in a very thin coating. In some embodiments, the vacuum coating layer has a thickness in the range of 10 to 600 nm, preferably 10 to 250 nm, and more preferably 50 to 250 nm. This can be compared to conventional aluminum foils used in packaging laminates, which typically have a thickness in the range of about 3 to 12 μm.

[0056] In some embodiments, the vacuum coating layer is formed on the first vapor barrier layer by physical vapor deposition (PVD) or chemical vapor deposition (CVD). The terms PVD and CVD also include atomic layer deposition (ALD) and deposition of diamond-like carbon (DLC) by PVD or CVD.

[0057] The vacuum coating layer may be inorganic or organic, hi some embodiments, the vacuum coating layer is an inorganic vacuum coating layer, such as a metal, metal oxide, or ceramic vacuum coating layer.

[0058] In some embodiments, the vacuum coated layer comprises a metal or metal oxide selected from the group consisting of aluminum, magnesium, silicon, copper, aluminum oxide, magnesium oxide, silicon oxide, and combinations thereof, preferably aluminum or aluminum oxide.

[0059] The vacuum coated layer is an inorganic vacuum coated layer, such as a metal, metal oxide, or ceramic vacuum coated layer.

[0060] One preferred type of vacuum coating, often used for its barrier properties, particularly water vapor barrier properties, is a physical vapor deposition (PVD) coating of aluminum metal. Such coatings consist essentially of aluminum metal and can typically have a thickness of 50 to 250 nm, although thicknesses less than 50 nm are also useful and may be preferred in some embodiments. The thickness of the vacuum coating layer represents less than 1% of the aluminum metal material typically present in aluminum foil of conventional thickness for packaging, i.e., 6.3 μm. Thus, in some embodiments, the vacuum coating layer comprises aluminum.

[0061] The thickness of the vacuum coated layer can also be characterized by the optical density of the layer. In some embodiments, the vacuum coated layer has an optical density greater than 1.8, preferably greater than 2.0, greater than 2.5, greater than 2.7, or greater than 3.0.

[0062] Aluminum oxide vacuum coated layers, also known as AlOx coatings, can provide similar barrier properties to aluminum metal coatings, but with the added advantage that thin AlOx coatings are transparent to visible light.

[0063] In some embodiments, the vacuum coating layer is an organic vacuum coating layer. In some embodiments, the vacuum coating layer comprises carbon.

[0064] The organic vacuum coating layer can be, for example, a vacuum coated carbon layer, such as a diamond-like carbon (DLC) layer formed from carbon or an organic compound.

[0065] In some embodiments, the vacuum coated layer has a thickness in the range of 10 to 600 nm, preferably in the range of 10 to 250 nm, and more preferably in the range of 50 to 250 nm.

[0066] A vacuum coating layer is formed on at least the first water vapor barrier layer. In some embodiments, a vacuum coating layer is formed on both the first and second water vapor barrier layers. The vacuum coating layer formed on the second water vapor barrier layer can be the same as or different from the vacuum coating layer formed on the first water vapor barrier layer.

[0067] The first and second water vapor barrier layers formed on the major surfaces of the paper or paperboard substrate prior to the vacuum coating process function to maintain the moisture content within the paper or paperboard substrate during the vacuum coating process. Thus, the moisture content of the coated paper or paperboard substrate is substantially the same as or slightly lower than the moisture content of the uncoated paper or paperboard substrate, preferably less than 3% by weight lower, more preferably less than 2% by weight lower, and most preferably less than 1% by weight lower. In some embodiments, the paper or paperboard substrate of the resulting coated paper or paperboard product has a moisture content in the range of 3.5 to 9% by weight, preferably in the range of 4 to 8% by weight, as determined in accordance with ISO 638.

[0068] Coated paper or paperboard products according to the present invention can provide excellent oxygen barrier properties, water vapor barrier properties, and liquid barrier properties.

[0069] In some embodiments, the resulting coated paper or paperboard product has a moisture content of 10 cc / m as measured according to ASTM standard D-3985 at 50% relative humidity and 23°C. 2 / 24h less than 5cc / m 2 / 24h or less, preferably 2cc / m 2 / Has an oxygen transmission rate (OTR) of less than 24h.

[0070] In some embodiments, the resulting coated paper or paperboard product has a modulus of 10 g / m 2 as measured according to ASTM standard F1249 at 50% relative humidity and 23° C. 2 / 24h less than 5g / m 2 / 24h or less, preferably 2g / m 2 / 24h water vapor transmission rate (WVTR) of less than

[0071] In some embodiments, a protective coating layer is formed on the vacuum coating layer. The protective coating layer protects the thin and delicate vacuum coating layer from scratches or damage that could lead to deterioration of the barrier properties provided by the vacuum coating layer. The protective coating layer can also provide additional barrier or other properties to the coated paper or paperboard product. The protective coating layer is also preferably heat-sealable.

[0072] In some embodiments, the method of the present invention comprises: e) forming a protective coating layer on the vacuum coated layer; Further includes:

[0073] In some embodiments, the protective coating layer is a polyethylene layer.

[0074] In some embodiments, the basis weight of the protective coating layer is from 8 to 50 g / m 2 in the range of 12 to 50 g / m 2 is in the range.

[0075] The coated paper or paperboard product obtainable by the method according to the first aspect is useful for the manufacture of paper or paperboard containers, particularly containers for liquid or food packaging. Thus, according to a second aspect set forth herein, there is provided a method for manufacturing a container, particularly a container for liquid or food packaging, said method comprising: a) producing a coated paper or paperboard product according to the method described herein with reference to the first aspect; and b) Converting coated paper or paperboard products into containers Includes.

[0076] Coated paper or paperboard products typically have a first, outermost surface intended to function as the exterior, or printing, surface, and a second, outermost surface intended to function as the interior surface of a container for liquid or food packaging. The surface of the coated paper or paperboard product that includes the vacuum coating layer is typically intended to face the interior of the container for liquid or food packaging. Thus, in some embodiments, the vacuum coating layer faces the interior of the container.

[0077] The coated paper or paperboard product obtained by the process of the present invention has a coating strength of at least 100 g / m 2 Weighing capacity: 900 kg / m 3 The present invention has a unique structure in which a paper or paperboard substrate having a density of less than 1000 kJ / cm2 and a moisture content of at least 3.5% by weight is sandwiched between first and second water vapor barrier layers and a vacuum coating layer formed on at least the first water vapor barrier layer, and the first water vapor barrier layer is formed from polyethylene having a melting point in the range of 90 to 120°C and having a density of 8 to 20 g / m2. 2 The weight ranges from 1000 to 10 ...

[0078] According to a third aspect presented herein, there is provided a coated paper or paperboard product comprising: At least 100 g / m, determined in accordance with ISO 638 2 Weighing capacity: 900 kg / m 3 a paper or paperboard substrate having a density of less than 1000 .mu.m and a moisture content of at least 3.5% by weight, the paper or paperboard substrate having a first major surface and a second major surface; a first water vapor barrier layer formed on a first major surface of the paper or paperboard substrate, the first water vapor barrier layer comprising a thermoplastic polymer; a second water vapor barrier layer formed on a second major surface of the paper or paperboard substrate, the second water vapor barrier layer comprising a thermoplastic polymer; and a vacuum coating layer formed on at least the first water vapor barrier layer; Including, The first water vapor barrier layer is formed from polyethylene having a melting point in the range of 90 to 120°C and having a density of 8 to 20 g / m 2 having a weight in the range of A coated paper or paperboard product is provided.

[0079] In some embodiments, the thermoplastic polymer is a polyolefin or a blend of polyolefins, more preferably polyethylene, polypropylene, or a blend or copolymer thereof. In some embodiments, the thermoplastic polymer is polyethylene. In preferred embodiments, the thermoplastic polymer is low density polyethylene (LDPE) or linear low density polyethylene (LLDPE).

[0080] The coated paper or paperboard product, the paper or paperboard substrate, the first water vapor barrier layer, the second water vapor barrier layer, and the vacuum coating layer may be further defined as described above with reference to the first aspect.

[0081] The coated paper or paperboard product can provide an alternative to traditional materials using aluminum foil layers and can be more easily repulped and recycled. In some embodiments, the coated paper or paperboard product has a reject rate of less than 30%, preferably less than 20%, and more preferably less than 10%, according to PTS RH 021 / 97.

[0082] Generally, products, polymers, materials, layers, and processes are described in terms of "comprising" various components or steps, but the products, polymers, materials, layers, and processes can also be said to "consist essentially of" or "consist of" the various components and steps.

[0083] While the present invention has been described with reference to various exemplary embodiments, it will be apparent to those skilled in the art that various modifications can be made and equivalents can be substituted for elements of the present invention without departing from the scope of the invention. In addition, many modifications can be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope of the invention. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but rather to include all embodiments falling within the scope of the appended claims.

Claims

1. 1. A method for producing a coated paper or paperboard product, said method comprising: a) at least 100 g / m2, determined in accordance with ISO 638 ２ Weight: 900 kg / m ３ providing a paper or paperboard substrate having a density of less than 1000 .mu.m and a moisture content of at least 3.5% by weight, said paper or paperboard substrate having a first major surface and a second major surface; b) forming a first water vapor barrier layer on a first major surface of a paper or paperboard substrate, said first water vapor barrier layer comprising a thermoplastic polymer; c) forming a second water vapor barrier layer on a second major surface of the paper or paperboard substrate, the second water vapor barrier layer comprising a thermoplastic polymer; and d) forming a vacuum coating layer on the first water vapor barrier layer to obtain a coated paper or paperboard product. Including, step (d) of forming a vacuum coating layer on the first water vapor barrier layer is performed after step (b) of forming the first water vapor barrier layer on the first major surface of the paper or paperboard substrate and after step (c) of forming a second water vapor barrier layer on the second major surface of the paper or paperboard substrate; method.

2. The paper or paperboard substrate has a dry weight of 115 to 600 g / m ２ in the range of 150 to 450 g / m ２ 10. The method of claim 1, wherein the weight is in the range of

3. The paper or paperboard substrate has a dry weight of 350 to 900 kg / m ３ in the range of 450 to 850 kg / m ３ 3. The method of claim 1 or 2, wherein the density is in the range of

4. 4. The method according to any one of claims 1 to 3, wherein the paper or paperboard substrate has a geometric mean bending resistance, measured according to ISO 2493 (L&W, 15°), of more than 150 mN, preferably more than 170 mN, more preferably more than 190 mN.

5. 5. The method of any one of claims 1 to 4, wherein the paper or paperboard substrate is multi-ply paperboard.

6. The method of any one of claims 1 to 5, wherein the paper or paperboard substrate comprises foamed paperboard.

7. 7. The method according to any one of claims 1 to 6, wherein the paper or paperboard substrate has a moisture content, determined in accordance with ISO 638, in the range of 3.5 to 9% by weight, preferably in the range of 4 to 8% by weight.

8. 8. The method of any one of claims 1 to 7, wherein the paper or paperboard substrate comprises a hydrophobic internal size, preferably selected from the group consisting of alkyl ketene dimer (AKD), alkenyl succinic anhydride (ASA), rosin sizing, fatty acids, fatty acid derivatives, and combinations thereof.

9. The paper or paperboard substrate has a hardness of at least 100 g / m2 measured according to ASTM standard F1249 at 50% relative humidity and 23°C. ２ / 24h, preferably at least 150g / m ２ / 24h, more preferably at least 200g / m ２ 9. The method of claim 1, wherein the composition has a water vapor transmission rate (WVTR) of 1 / 24h.

10. 10. The method of any one of claims 1 to 9, wherein the first water vapor barrier layer is formed by extrusion coating of a thermoplastic polymer or by dispersion coating of a dispersion comprising a thermoplastic polymer.

11. 11. The method according to any one of claims 1 to 10, wherein the first water vapor barrier layer is formed by extrusion coating of a thermoplastic polymer, preferably a polyolefin or a blend of polyolefins, more preferably polyethylene, polypropylene, or a blend thereof.

12. 12. The method of any one of claims 1 to 11, wherein the second water vapor barrier layer is formed by extrusion coating of a thermoplastic polymer or by dispersion coating of a dispersion comprising a thermoplastic polymer.

13. The first and second water vapor barrier layers each have a water vapor transmission rate (WVTR) of 75 g / m or less, measured in accordance with ASTM standard F1249 at 50% relative humidity and 23°C of a paper or paperboard substrate coated with the water vapor barrier layers. ２ / 24h or less, preferably 50g / m ２ / 24h or less, more preferably 30g / m ２ 13. The method of claim 1, wherein the temperature is reduced to less than 24 hours.

14. The first and second water vapor barrier layers each have a water vapor barrier strength of 50 g / m2, measured in accordance with ISO standard 535. ２ Less than Cobb ６００ 14. The method of claim 1, wherein the value of

15. 15. The method of any one of claims 1 to 14, wherein the vacuum coating layer is formed on the first vapor barrier layer by physical vapor deposition (PVD) or chemical vapor deposition (CVD).

16. 16. The method of any one of claims 1 to 15, wherein the vacuum coating layer is an inorganic vacuum coating layer, such as a metal, metal oxide, or ceramic vacuum coating layer.

17. The resulting coated paper or paperboard product has a viscosity of 10 cc / m2 measured in accordance with ASTM standard D-3985 at 50% relative humidity and 23°C. ２ / 24h less, preferably 5cc / m ２ / 24h or less, more preferably 2cc / m ２ 17. The method of claim 1, wherein the composition has an oxygen transmission rate (OTR) of less than 1 / 24h.

18. The resulting coated paper or paperboard product has a modulus of elasticity of 10 g / m 2 measured according to ASTM standard F1249 at 50% relative humidity and 23°C. ２ / 24h or less, preferably 5g / m ２ / 24h or less, more preferably 2g / m ２ 18. The method of claim 1, wherein the composition has a water vapor transmission rate (WVTR) of less than 1 / 24h.

19. e) forming a protective coating layer on the vacuum coated layer; 19. The method of any one of claims 1 to 18, further comprising:

20. 1. A coated paper or paperboard product comprising: At least 100 g / m2, determined in accordance with ISO 638 ２ Weight: 900 kg / m ３ a paper or paperboard substrate having a density of less than 1000 .mu.m and a moisture content of at least 3.5% by weight, said paper or paperboard substrate having a first major surface and a second major surface; a first water vapor barrier layer formed on a first major surface of the paper or paperboard substrate, the first water vapor barrier layer comprising a thermoplastic polymer; a second water vapor barrier layer formed on a second major surface of the paper or paperboard substrate, the second water vapor barrier layer comprising a thermoplastic polymer; and a vacuum coating layer formed on at least the first water vapor barrier layer; Including, The first water vapor barrier layer is formed from polyethylene having a melting point in the range of 90 to 120°C and having a density of 8 to 20 g / m ２ having a weight in the range of Coated paper or paperboard products.

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