Method for Producing a Barrier Layer for a Paper or Paperboard Based Packaging Laminate - Patent application

Abstract

The present invention relates to a method for producing a barrier layer for a paper or paperboard based packaging laminate, the method comprising: a) providing a barrier substrate comprising at least 50% by weight, based on the dry weight of the barrier substrate, of highly refined cellulose pulp (HRC), the HRC having a Shopper-Riegler (SR) number greater than 80, determined in accordance with ISO standard 5267-1; b) providing a transfer coating substrate comprising a vacuum coating layer and a backing layer separated by a release layer; and c) Transferring the vacuum coating layer from the backing layer to the barrier substrate by a transfer coating process using an adhesive layer applied to the barrier substrate and / or the vacuum coating layer to obtain a barrier layer for paper or paperboard based packaging laminates.

Description

[Technical field]

[0001] The present disclosure relates to a barrier layer for paper or paperboard based packaging materials. More specifically, the present disclosure relates to a barrier layer for paper or paperboard based packaging materials that has a low oxygen transmission rate (OTR) and a low water vapor transmission rate (WVTR). [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. Paper or board with a relatively small amount of suitable plastic material uniformly can provide the necessary properties to make the paper or board suitable for many demanding applications (e.g., liquid or food packaging board). In liquid or food packaging boards, polyolefin coatings are often used as liquid barrier layers, heat seal layers and adhesives. However, such polymer-coated boards are difficult to recycle because the polymer is difficult to separate from the fibers.

[0003] In addition, in many cases, the water vapor barrier properties of polymer-coated paper or paperboard are still 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, the addition of polymer and aluminum foil entails a significant cost increase, and the combination of polymer coating layer and aluminum foil makes the material more difficult to recycle. Also, due to its high carbon footprint, it is desirable to replace aluminum foil in paper and paperboard-based packaging materials.

[0004] Aseptic packaging for long shelf life such as milk and juice is usually made from a liquid or food packaging board that includes a multi-layered paperboard-based substrate, an outermost layer of heat-sealable polyolefin (e.g. polyethylene: PE) and an innermost layer of polyolefin and aluminium. An aluminium foil layer (necessary to provide barrier properties against water vapour and oxygen) is usually incorporated between the polyethylene layers resulting in the following structure: PE / paperboard / PE / aluminum / PE.

[0005] In the prior art, attempts have been made to replace aluminum foil with more environmentally friendly and / or easier to recycle solutions, but so far without any real success.For example, microfibrillated cellulose (MFC) films and coatings have been developed, in which defibrillated cellulose fibrils are dispersed, for example, in water, and then reorganized and recombined together to form a dense film or coating with excellent gas barrier properties.Unfortunately, the water vapor and gas barrier properties of such MFC films tend to deteriorate at high humidity.

[0006] One solution discussed in the prior art is to deposit a thin vacuum coating layer directly onto the MFC film or coating, for example using chemical or physical vapor deposition techniques. The thin vacuum coating layer can be, for example, aluminum (Al2O3, AlO x ) or SiO xThe problem with these deposition techniques is that the coating process is carried out under vacuum, which means that the substrate needs to be degassed. For MFC films and coatings, this means increased costs for the process, but degassing also means drying the substrate to a very low moisture content. This drying, and subsequent re-hydration to ambient moisture levels, changes the mechanical properties of the MFC films and coatings. Not only does this drying increase the crack tendency and post-convertability of the MFC films and coatings, but there is also a risk of significantly increased cracking of the thin and sensitive vacuum coating layers when the film or coating is re-hydrated.

[0007] Thus, there remains a need for improved solutions to replace the combination of plastic films and aluminum foil in paper and paperboard based packaging materials while maintaining acceptable barrier properties against liquids, water vapor and oxygen. At the same time, there is a need to replace the combination of plastic films and aluminum foil with alternatives that facilitate repulping and recycling of the packaging materials used.

[0008] Detailed Description of the Invention The objective 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 in packaging materials (e.g., liquid or food packaging cardboard).

[0009] It is a further object of the present disclosure to provide a barrier layer for paper or paperboard based packaging laminates (e.g., liquid or food packaging cardboard) that provides good water vapor barrier properties even at relatively high humidity and temperature.

[0010] A further object of the present disclosure is to provide a method for treating a pulmonary circulation disorder (PWD) having a PWD of 10 cc / cm2, measured at 50% relative humidity and 23° C. according to ASTM standard D-3985. 2The object of the present invention is to provide a barrier layer having an oxygen transmission rate (OTR) of less than 1 / 24h.

[0011] A further object of the present disclosure is to provide a method for manufacturing a viscoelastic material having a viscosity of 10 g / m2, measured according to 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.

[0012] It is a further object of the present disclosure to provide a barrier layer for paper or paperboard based packaging laminates (e.g., liquid or food packaging cardboard) that facilitates repulping of the packaging laminate as compared to packaging laminates using traditional combinations of plastic films and aluminum foil.

[0013] The above objectives, as well as other objectives which will be recognized by those skilled in the art in light of this disclosure, are accomplished by various aspects of the present disclosure.

[0014] The present invention is based on the realization that a very thin coating layer, typically having a thickness in the range of 20-600 nm, more preferably in the range of 50-250 nm, formed by a vacuum deposition process (e.g. physical vapor deposition (PVD) or chemical vapor deposition (CVD)), when combined with a substrate formed of highly refined cellulose pulp (HRC) or microfibrillated cellulose (MFC), can provide better barrier properties against oxygen and water vapor compared to those of thicker aluminum foils. Since the thickness of the vacuum deposited coating is typically at least an order of magnitude less than the thickness of conventional foils, the metal content of the product can be significantly reduced.

[0015] However, vacuum-deposited coatings directly on the substrate to be coated (so-called direct vacuum coating or direct metallization) have proven problematic for substrates made of highly refined cellulose pulp (HRC) or microfibrillated cellulose (MFC). More specifically, the degassing associated with the vacuum treatment means that the substrate is dried to a very low moisture content. This drying, and the subsequent rehydration to ambient moisture levels, alters the mechanical properties of the HRC or MFC substrate. This drying not only increases the substrate's crack tendency and subsequent variability, but also increases the risk of significantly increasing cracking of the thin and sensitive vacuum coating layer when the substrate is rehydrated.

[0016] The present invention is based on the discovery that these problems can be overcome by replacing direct vacuum deposition coating of the substrate by a transfer coating technique, thus avoiding vacuum processing of the barrier substrate.

[0017] According to a first aspect described herein, there is provided a method of producing a barrier layer for a paper or paperboard based packaging laminate, the method comprising: a) providing a barrier substrate comprising at least 50% by weight, based on the dry weight of the barrier substrate, of highly refined cellulose pulp (HRC), the HRC having a Shopper-Riegler (SR) number greater than 80, determined in accordance with ISO standard 5267-1; b) providing a transfer coating substrate comprising a vacuum coating layer and a backing layer separated by a release layer; and c) transferring the vacuum coating layer from the backing layer to the barrier substrate by a transfer coating process using an adhesive layer applied on the barrier substrate and / or the vacuum coating layer to obtain a barrier layer for a paper or paperboard based packaging laminate. It includes.

[0018] Transfer coating of vacuum deposited coating layers (also commonly referred to as transfer metallization when the coating contains metal) is a conventional method used in producing decorative layers on graphical paper substrates. The inventors have found that this coating technique, when combined with substrates made of highly refined cellulose pulp (HRC) or microfibrillated cellulose (MFC), can be used to form highly useful barrier layers against oxygen and water vapor suitable for paper or paperboard based packaging laminates. In addition to providing good barrier properties against oxygen and water vapor, the barrier layer according to the invention can also form a good barrier against other gases, as well as against scents and odors.

[0019] Thus, the barrier substrate used in the method according to the invention comprises highly refined cellulose pulp. Refining or beating of cellulose pulp refers to subjecting cellulose fibers to mechanical treatment and modification in order to give them the desired properties. Highly refined cellulose fibers can be produced from a variety of raw materials, for example softwood pulp or hardwood pulp. Highly refined cellulose fibers are preferably cellulose fibers that have never been dried.

[0020] The barrier substrate comprises at least 50% highly refined cellulose pulp (HRC) by weight, based on the dry weight of the barrier substrate, hi some embodiments the barrier substrate comprises at least 70% highly refined cellulose pulp, preferably at least 90% by weight, based on the dry weight of the barrier substrate.

[0021] The HRC has a Schopper-Riegler (SR) number, determined according to ISO standard 5267-1, greater than 80. In some embodiments, the highly refined cellulose pulp has a Schopper-Riegler (SR) number, determined according to ISO standard 5267-1, greater than 85, preferably greater than 90.

[0022] In some embodiments, the highly refined cellulose pulp is microfibrillated cellulose (MFC).

[0023] In the context of this patent application, microfibrillated cellulose (MFC) is intended to mean cellulose particles, fibres or fibrils having a width or diameter between 20 nm and 1000 nm.

[0024] There are various methods for making MFC (e.g. purification by single or multiple routes), including prior hydrolysis followed by purification or high shear degradation or liberation of fibrils. One or more pretreatment steps are usually required to make MFC production energy efficient and sustainable. Thus, the cellulose fibers of the pulp used in producing MFC may be natural or may have been enzymatically or chemically pretreated, for example to reduce the amount of hemicellulose or lignin. The cellulose fibers may be chemically modified before fibrillation, where the cellulose molecules have different (or more) functional groups than found in the original cellulose. Such groups are in particular carboxymethyl (CM), aldehyde, and / or carboxy groups (cellulose obtained by N-oxyl mediated oxidation, e.g. "TEMPO"), or quaternary ammonium (cationized cellulose). After modification or oxidation by one of the above methods, the fibers are easier to decompose into MFC.

[0025] MFCs can be produced from wood-based cellulose fibers, both hardwood or softwood fibers. MFCs can also be produced from microbial sources, agricultural fibers (e.g., wheat straw pulp, bamboo, bagasse), or other non-wood fiber sources. MFCs can be produced from pulp (including pulp from virgin fibers), such as mechanical, chemical, and / or thermomechanical pulp. MFCs can also be produced from shredded or recycled paper.

[0026] The barrier substrate is preferably formed from an aqueous dispersion of highly refined cellulose pulp, which is then formed into a sheet or web, dewatered and / or dried. Formation, dewatering and drying of the barrier substrate can be accomplished using methods known in the art, including, but not limited to, casting on a solid surface and subsequent drying, forming a paper or paperboard substrate and subsequent dewatering and drying, and forming on a paper machine wire and subsequent dewatering and drying.

[0027] Depending on how the barrier substrate is manufactured, it may be considered as a free-standing barrier substrate film or as a coating layer onto a paper or paperboard substrate.

[0028] In some embodiments, the barrier substrate has a coating thickness of 2 to 100 g / m 2 in the range of 2 to 60 g / m 2 More preferably, the range is 2 to 50 g / m 2 The grammage ranges from 100 to 150 g / g.

[0029] In some embodiments, the barrier substrate is a free-standing barrier substrate film. As used herein, the term "film" generally refers to a material formed into a thin continuous sheet. Depending on the composition of the barrier substrate film, the film may also be considered as a thin paper or even a membrane. The free-standing barrier substrate preferably has sufficient thickness, mechanical strength, and rigidity for handling (e.g., winding, unwinding, coating and / or laminating to paper or paperboard substrates). Barrier substrates in the form of free-standing barrier substrate films typically have a weight of 2 to 100 g / m 2 in the range of 2 to 60 g / m 2 More preferably, the range is 2 to 50 g / m 2 The composition has a basis weight in the range of 1000 to 2000 g.

[0030] In some embodiments, the barrier substrate is not a free-standing barrier substrate film, but a coating layer on a paper or paperboard substrate. When the barrier substrate is formed or coated on a paper or paperboard substrate and then dewatered and dried, the barrier substrate thus obtained can also be considered as a coating layer on a paper or paperboard substrate. A barrier substrate in the form of a coating layer on a paper or paperboard substrate can be made significantly thinner than a free-standing barrier substrate film, since mechanical strength and rigidity for handling can be provided by the paper or paperboard substrate. A barrier substrate in the form of a coating layer on a paper or paperboard substrate typically has a thickness of 2 to 20 g / m 2 in the range of 2 to 15 g / m 2 More preferably, the range is 2 to 10 g / m 2 The composition has a basis weight in the range of 1000 to 2000 g.

[0031] The barrier substrate is typically relatively dense. In some embodiments, the barrier substrate has a density of 800 kg / m 3 More than 900 kg / m 3 Unless otherwise stated, density is determined according to ISO standard 534.

[0032] In some embodiments, the barrier substrate has a Gurley Hill value, measured according to ISO standard 5636-5, of greater than 5000 s / 100 ml, preferably greater than 20,000 s / 100 ml, and more preferably greater than 42,300 s / 100 ml.

[0033] The method according to the invention is particularly advantageous for substrates that are difficult to dry completely or are expensive to dry completely. Because the method does not involve subjecting the barrier substrate itself to a vacuum coating process, it is acceptable for the barrier substrate to have a relatively high moisture content when subjected to a transfer coating process. Thus, in some embodiments, the barrier substrate has a moisture content of 1.5% by weight or more, preferably 2% by weight or more, more preferably 3% by weight or more, or 3.5% by weight or more, or 4% by weight or more when subjected to a transfer coating process. The moisture content of the barrier substrate is preferably 15% by weight or less, 12% by weight or less, 10% by weight or less, or 9% by weight or less. In some embodiments, the barrier substrate has a moisture content of 4% by weight or more, for example, a moisture content in the range of 4-15% by weight, 4-12% by weight, 5-10% by weight, or 6-9% by weight. Unless otherwise stated, the moisture content is determined according to ISO standard 638.

[0034] Barrier substrates that contain at least 50% by weight of highly refined cellulose pulp (HRC), based on the weight of the barrier substrate, typically have a relatively low resistance to water vapor. In some embodiments, the barrier substrate has a water vapor resistance of 30 g / m2, measured according to ASTM standard F1249 at 50% relative humidity and 23° C. 2 / With a water vapor transmission rate (WVTR) of over 24 hours,

[0035] A vacuum coating layer is applied onto the prepared barrier substrate by a transfer coating process to provide a barrier layer for paper or paperboard based packaging laminates. Transfer coating (also commonly referred to as transfer metallization when the coating includes metal) generally involves transferring a thin vacuum coating layer from a transfer coating substrate to a substrate to be coated with an adhesive layer applied between the vacuum coating layer and the substrate to be coated.

[0036] The transfer coating substrate comprises a vacuum coating layer and a backing layer separated by a release layer that has low adhesion to the vacuum coating layer and / or the backing layer, such that the vacuum coating layer is readily separable from the backing layer.

[0037] For the transfer coating process, an adhesive layer is applied on the barrier substrate or on the vacuum coating layer or on both. The vacuum coating layer is transferred to the barrier substrate using an adhesive layer applied on the barrier substrate and / or on the vacuum coating layer. The vacuum coating layer contacts and is adhered to the barrier substrate using an adhesive layer applied on the barrier substrate and / or on the vacuum coating layer. Once the vacuum coating layer is adhered to the barrier substrate, the backing layer is removed from the vacuum coating layer, leaving the adhered vacuum coating layer, and optionally the release layer, on the barrier substrate. Any additional layers between the release layer and the vacuum coating layer and / or on top of the vacuum coating layer will also remain on the barrier substrate.

[0038] In some embodiments, the transfer coating process comprises: contacting and adhering the vacuum coating layer to the barrier substrate using an adhesive layer applied on the barrier substrate and / or the vacuum coating layer; and Removing the backing layer, leaving the vacuum coating layer and, optionally, the release layer on the barrier substrate; Includes.

[0039] The vacuum coating layer in contact with the barrier substrate through an adhesive layer can be subjected to various treatments to improve adhesion between the vacuum coating layer and the barrier substrate. In some embodiments, the vacuum coating layer in contact with the barrier substrate through an adhesive layer is subjected to pressure, heat, and / or radiation to improve adhesion between the vacuum coating layer and the barrier substrate.

[0040] The temperature may vary depending on the contact time and pressure, but is generally in the range of 40 to 250° C., preferably in the range of 60 to 150° C. The pressure should be high enough to allow good transfer of the vacuum coating layer. In some embodiments, the pressure is in the range of 1 to 50 kg / cm. The pressure and heat may be provided, for example, by a heated nip or an extended nip.

[0041] Transfer coating substrates similar to those for use in the present invention are known in the art, for example for providing a decorative layer on a graphical paper substrate. However, since the objective of the method of the present invention is to provide a barrier layer, the composition, shape and thickness of the vacuum coating layer may differ from those used for decorative purposes. Transfer coating substrates are usually produced by coating a backing layer, preferably a polymer film, with a release layer. The vacuum coating layer is then deposited on the release layer. Optionally, an additional intermediate layer may be added between the release layer and the vacuum coating layer, and / or a top layer may be added on top of the vacuum coating layer. The additional layer may include a protective layer to protect the sensitive vacuum coating layer before the coating layer is separated from the backing layer (protective top layer on top of the vacuum coating layer) or after the vacuum coating layer is separated from the backing layer (protective intermediate layer between the release layer and the vacuum coating layer). The additional intermediate layer or top layer may also include a barrier layer, for example a barrier layer against gas or moisture, or a primer layer to improve adhesion of the vacuum coating layer.

[0042] The backing layer primarily serves as a carrier for the release layer and the vacuum coating layer. The backing layer preferably provides suitable mechanical and strength properties for the transfer coating process, as well as a pinhole-free surface for forming the release layer and the vacuum coating layer. In some embodiments, the backing layer comprises a plastic film. The plastic film can be, for example, a polyethylene terephthalate (PET) film, although those skilled in the art will appreciate that other polymer films are also useful. After being removed from the vacuum coating layer during the transfer coating process, the backing layer may preferably be reusable.

[0043] Release layers for transfer coating applications are known in the art. They can have many different chemical compositions, with the common feature of relatively low adhesion to the substrate, so that they can be easily removed or peeled from the substrate. Examples of common materials for use in release layers include, but are not limited to, film-forming vinyl chloride-vinyl acetate copolymers, or film-forming vinylidene chloride copolymers, or combinations thereof.

[0044] In some embodiments, the release layer comprises a layer of material that provides a lower adhesion of the adhesive layer to the barrier substrate and to the vacuum coating layer than it provides to the backing layer or to the vacuum coating layer. In this way, the vacuum coating, and optionally also the release layer, will remain on the adhesive layer when the backing layer is removed.

[0045] When the backing layer is removed, the release layer may remain on the backing layer or on the vacuum coating layer, depending on the adhesive properties of the release layer. Of course, to achieve certain manufacturing and performance, it is preferred that the release layer is not retained partially on the backing layer and partially on the vacuum coating layer when the backing layer is removed. The release layer is preferably selected to have significantly stronger adhesion to the backing layer or the vacuum coating layer than the other, so that when the backing layer is removed, the entire release layer remains on one of the two surfaces. In some embodiments, the release layer comprises a layer of material that is less adhesive to the backing layer than to the vacuum coating layer, or a layer of material that is less adhesive to the vacuum coating layer than to the backing layer, so that when the backing layer is removed, the entire release layer remains on the vacuum coating layer or on the backing layer. When the backing layer is removed, it is usually preferred that the release layer remains on the vacuum coating layer, because the backing layer can then be conveniently recoated and reused. Thus, in some embodiments, the release layer is selected such that the adhesion between the vacuum coating layer and the release layer is significantly stronger than that between the release layer and the backing layer, so that when the backing layer is removed, the entire release layer remains on the surface of the vacuum coating layer. The release layer on the surface of the vacuum coating layer will then act as a protective coating or varnish on the vacuum coating layer. Furthermore, during the transfer coating process, the backing layer from which both the vacuum coating layer and the release layer have been removed can be conveniently reused when producing a new transfer coating substrate. If an intermediate polymer layer is applied between the release layer and the vacuum coating layer, the intermediate polymer layer will remain on the surface of the vacuum coating layer when the backing layer is removed, and the intermediate polymer layer on the surface of the vacuum coating layer will also act as a protective coating on the vacuum coating layer. As an example, a carrier film (e.g., a PET film) is provided with a release layer (0.05-5 gsm), a protective coating (0.5-15 gsm) on top of the release layer, and then a thin vacuum coating layer on top of the protective coating.In some embodiments, an adhesive layer may also be provided on top of the vacuum coating layer. In addition to acting as an adhesive when the vacuum coating layer is transferred to the paper or paperboard substrate, the adhesive layer may also act as a protective coating for the vacuum coating layer during shipping and handling.

[0046] The vacuum coating layer is formed on the release layer or on an additional polymer layer applied on top of the release layer. Vacuum coating refers to a family 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. The 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.

[0047] Vacuum coating typically results in a very thin coating. In some embodiments, the vacuum coating layer has a thickness in the range of 10-600 nm, preferably in the range of 10-250 nm, more preferably in the range of 50-250 nm. This should be compared to conventional aluminum foils used in packaging laminates, which typically have a thickness in the range of 3-12 μm.

[0048] The vacuum coating layer can be inorganic or organic, hi some embodiments, the vacuum coating layer comprises an inorganic vacuum coating layer (e.g., metal, metal oxide), or a ceramic vacuum coating layer.

[0049] In some embodiments, the vacuum coating 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.

[0050] One of the preferred vacuum coatings, often used for its barrier properties (especially water vapor barrier properties), is an aluminum metal physical vapor deposition (PVD) coating. Such coatings (consisting essentially of aluminum metal) can typically have a thickness of 50-250 nm. However, thicknesses even less than 50 nm can be useful and even preferred in some embodiments. The thickness of the vacuum coating layer corresponds to less than 1% of the aluminum metal material typically present in packaging aluminum foils of conventional thickness (i.e. 6.3 μm) for packaging. Thus, in some embodiments, the vacuum coating layer comprises aluminum.

[0051] 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.

[0052] Aluminum oxide vacuum coating layer (AlO x Coatings, also known as aluminium oxide coatings, can provide similar barrier properties to aluminium metal coatings, but with the added benefit of being thin AlO x The coating is transparent to visible light.

[0053] In some embodiments, the vacuum-coated layer comprises an organic vacuum-coated layer, which can be, for example, a vacuum-coated carbon layer, such as a diamond-like carbon (DLC) layer formed from carbon or an organic compound.

[0054] The transfer coating substrate may further include a protective layer applied on top of the vacuum coating layer to protect the thin and sensitive vacuum coating layer during manufacturing, handling, and shipping prior to the transfer coating process. The protective layer applied on top of the vacuum coating layer may remain on top of the vacuum coating layer during the transfer coating process and form part of the resulting barrier layer. Alternatively, in some embodiments, the protective layer applied on top of the vacuum coating layer may be removed prior to the transfer coating process.

[0055] During the transfer coating process, the vacuum coating layer is transferred from the backing layer to the barrier substrate with the aid of an adhesive layer applied over the barrier substrate and / or the vacuum coating layer to provide a barrier layer for the paper or paperboard based packaging laminate. Many different types of adhesives and adhesive coating methods can be used with the present invention.

[0056] The adhesive layer typically comprises one or more adhesive polymers. The adhesive layer may consist entirely of one or more adhesive polymers or may also comprise other additives to facilitate the coating process or to improve the properties of the adhesive layer.

[0057] In some embodiments, the adhesive layer comprises at least 50% by weight of an adhesive polymer or mixture of adhesive polymers on a dry weight basis.

[0058] In some embodiments, the adhesive layer comprises one or more adhesive polymers selected from the group consisting of polyolefins, polyurethanes, and acrylic copolymers.

[0059] In some embodiments, the adhesive layer comprises at least 50% by weight of a water-soluble polymer or mixture of water-soluble polymers based on dry weight. The water-soluble polymer of the adhesive layer is soluble in cold water or soluble in hot water at a given time (e.g., at temperatures below 100°C or even above 100°C). In addition to acting as an adhesive for the vacuum coating layer, the water-soluble polymer facilitates the separation of the vacuum coating layer and the optional additional plastic layer applied on top of the adhesive layer or vacuum coating layer during repulping. In some embodiments, the water-soluble polymer is selected from the group consisting of polyvinyl alcohol (PVOH), carboxymethyl cellulose (CMC), starch, alginate, and hemicellulose, and is preferably PVOH.

[0060] The adhesive layer can be applied by any suitable method known in the art. The adhesive layer can be applied, for example, using liquid coating methods known in the art, as a solution or dispersion in an aqueous or organic carrier solvent, in melt form using extrusion coating, or in the form of a solid film by lamination. In a preferred embodiment, the adhesive layer is applied onto the barrier substrate and / or vacuum coating layer as a solution or dispersion in an aqueous carrier. Thus, in other words, the adhesive is preferably a water-based adhesive.

[0061] Depending on the adhesive layer, the transfer coating process can be carried out as a wet bond or dry bond lamination process. Depending on the adhesive layer, the transfer coating process can be carried out in the form of a solution or dispersion in an aqueous or organic carrier solvent (e.g., in the case of liquid adhesive lamination), in molten form (e.g., in the case of extrusion coating lamination), or in the form of a solid film (e.g., in the case of adhesive film lamination). In some embodiments, the adhesive layer is applied onto the barrier substrate and / or the vacuum coating layer as a solution or dispersion in an aqueous or organic carrier solvent, partially or completely dried onto the barrier substrate and / or the vacuum coating layer, and then the vacuum coating layer is contacted with the barrier substrate and bonded to the barrier substrate using the adhesive layer. The completely dried adhesive layer can be bonded to the barrier substrate by a dry bond lamination process using pressure, heat and / or radiation.

[0062] The adhesive layer may be applied directly to the barrier substrate surface, or may be applied first to the vacuum coating layer and then to the barrier substrate together with the vacuum coating layer, or both. The advantage of applying an adhesive coating to both surfaces is that wetting of the surfaces is reduced.

[0063] To minimize the risk of pinholes in the adhesive layer, the adhesive layer is preferably applied in at least two coating steps, with the coated film drying between these steps.

[0064] The adhesive layer is preferably formed by a liquid film coating process, i.e. in the form of a solution or dispersion, which is applied by spreading the solution or dispersion on the substrate in a thin, uniform layer and then drying. The liquid phase of the solution or dispersion is preferably water or an aqueous solution, but organic solvents or mixtures of water or aqueous solutions with organic solvents can also be used. The adhesive polymer or polymers can be present in the solution or dispersion in dissolved form or in the form of polymer particles (e.g. latex). The adhesive layer 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, flexo coating, gate roll coating, twin roll HSM coating, blade coating (e.g. short dwell time blade coating), jet applicator coating, spray coating, gravure coating, or reverse gravure coating.

[0065] In some embodiments, at least one adhesive layer is applied in the form of a foam. Foam coating is advantageous because it allows film formation at higher solids content and lower water content than non-foam coating. The lower water content in foam coating also reduces the problem of rewetting the barrier substrate. The foam can be formed using polymeric or non-polymeric foaming agents. Examples of polymeric foaming agents include PVOH, hydrophobically modified starch, and hydrophobically modified ethyl hydroxyethyl cellulose.

[0066] In some embodiments, the adhesive layer further comprises a crosslinking agent capable of crosslinking the water-soluble polymer. The crosslinking agent may advantageously be applied together with the water-soluble polymer and then activated (e.g., by heat or radiation) when the adhesive layer is in contact with the vacuum coating layer. Crosslinking improves the water vapor barrier properties of the adhesive layer. Suitable crosslinking agents include, but are not limited to, polyfunctional organic acids or aldehydes, such as citric acid, glyoxal, and glutaraldehyde. In some embodiments, the crosslinking agent is an organic acid, more preferably citric acid. The concentration of the crosslinking agent may be, for example, 1-20% by weight, preferably 1-15% by weight, based on the dry weight of the adhesive layer.

[0067] In some embodiments, the adhesive layer comprises PVOH and citric acid. Crosslinking the PVOH with citric acid improves the water vapor barrier properties of the adhesive layer. In addition, it has been found that crosslinking the PVOH with citric acid in contact with the vacuum coating layer further improves the adhesion of the vacuum coating layer and the overall water vapor barrier properties of the barrier layer.

[0068] In some embodiments, the adhesive layer comprises one or more additional polymers in a total amount of 0-50 wt % based on dry weight. The one or more additional polymers may act to crosslink and / or further improve adhesion to the vacuum coating layer. Suitable one or more additional polymers include, but are not limited to, polyvinylpyrrolidone, polyvinylamide, polyvinylethyleneimine, polyacrylamide, cationic polyacrylamide, polyurethane, and derivatives thereof. Other suitable one or more additional polymers include latexes, such as styrene acrylate latex (SA latex), styrene butadiene latex (SB latex), polyvinyl acetate (PVAc), styrene butadiene acrylonitrile (SBN), polyvinylidene dichloride (PVDC), and hybrid polymer emulsions, such as grafted starch.

[0069] The basis weight of the adhesive layer is generally 1 to 20 g / m 2 In some embodiments, the basis weight of the adhesive layer may range from 2 to 15 g / m 2 More preferably, the range is 3 to 12 g / m 2 is in the range.

[0070] In some embodiments, the adhesive layer further comprises up to 50% by weight, based on dry weight, of microfibrillated cellulose (MFC), nanocrystalline cellulose, chemically modified cellulose derivatives such as sodium carboxymethylcellulose, hydroxypropyl cellulose, ethyl hydroxyethyl cellulose, cellulose acetate, hydroxyethyl cellulose, hemicellulose, or combinations thereof.

[0071] The vacuum coating layer is transferred from the backing layer to the barrier substrate by a transfer coating process using an adhesive layer applied over the barrier substrate and / or the vacuum coating layer.

[0072] In some embodiments, the adhesive layer is applied onto the barrier substrate and / or the vacuum coating layer as a solution or dispersion of the adhesive in an aqueous or organic carrier solvent, partially or completely dried on the barrier substrate and / or the vacuum coating layer, and then the vacuum coating layer is contacted with the barrier substrate and bonded to the barrier substrate using the adhesive layer. Partially dried generally means that the adhesive layer after drying has a total solids content below 90% by weight, preferably below 70% by weight, more preferably below 50% by weight. Fully dried generally means that the adhesive layer after drying has a total solids content above 90% by weight, preferably above 95% by weight, more preferably above 98% by weight. By partially or completely drying the adhesive layer before contacting and bonding the vacuum coating layer to the barrier substrate, the risk of blister formation between the vacuum coating layer and the barrier substrate during or after the transfer coating process is reduced.

[0073] In some embodiments, the adhesive layer is applied to the vacuum coating layer as a solution or dispersion of the adhesive in an aqueous or organic carrier solvent, partially or completely dried on the vacuum coating layer, and then the vacuum coating layer is contacted with the barrier substrate and adhered to the barrier substrate using the adhesive layer. It is particularly advantageous to apply a solution or dispersion of the adhesive especially on the vacuum coating layer, partially or completely dried, and then the vacuum coating layer is contacted with the barrier substrate and adhered to the barrier substrate using the adhesive layer. This reduces the risk of blister formation between the vacuum coating layer and the barrier substrate, as well as allowing reduced wetting of the water sensitive barrier substrate during the transfer coating process. In embodiments where the adhesive layer is applied to the vacuum coating layer and completely dried, it is further advantageous that the dried adhesive layer acts as a protective layer to protect the sensitive vacuum coating layer before the coating layer is separated from the backing layer.

[0074] In some embodiments, the adhesive layer comprises a first adhesive layer and a second adhesive layer, where the first and second adhesive layers can comprise the same adhesive or different adhesives.

[0075] In some embodiments, a first adhesive layer is applied onto the vacuum coating layer as a solution or dispersion of the adhesive in an aqueous or organic carrier solvent and allowed to dry partially or completely on the vacuum coating layer. A second adhesive is applied either onto the first adhesive layer or onto the barrier substrate, or both. Applying the second adhesive layer onto the first adhesive layer is preferred as it allows for reduced wetting of water sensitive barrier substrates.

[0076] The first and second adhesive layers may comprise the same adhesive or different adhesives. In some embodiments, the first and second adhesive layers comprise different adhesives. In some embodiments, the first adhesive layer is selected to provide good adhesion to the vacuum coating layer, and the second adhesive layer is selected to provide good adhesion to the barrier substrate and / or other useful properties, such as barrier properties. In some embodiments, the first adhesive layer comprises at least 50% polyurethane by weight based on dry weight. The polyurethane in the first adhesive layer is advantageous because it provides good adhesion to the vacuum coating layer. In some embodiments, the second adhesive layer comprises at least 50% PVOH by weight based on dry weight. The PVOH in the second adhesive layer is advantageous because it provides good adhesion to the barrier substrate and good gas barrier properties, and facilitates separation of the vacuum coating layer from the optional additional plastic layer applied on top of the adhesive layer or the vacuum coating layer during repulping.

[0077] In a more specific embodiment, the vacuum coating layer comprises an aluminum or aluminum oxide vacuum coating layer and the adhesive layer comprises at least 50% polyurethane by weight on a dry weight basis.

[0078] In another more specific embodiment, the vacuum coating layer comprises an aluminum or aluminum oxide vacuum coating layer and the adhesive layer comprises at least 50% by weight PVOH and 1-20% by weight organic acid on a dry weight basis.

[0079] In another more specific embodiment, the vacuum coating layer comprises an aluminum or aluminum oxide vacuum coating layer, a first adhesive layer applied over the vacuum coating layer comprises at least 50% polyurethane by weight on a dry weight basis, and a second adhesive layer applied over either the first adhesive layer or the barrier substrate or both comprises at least 50% PVOH by weight on a dry weight basis. This particular configuration has been found to provide a particularly useful combination of good adhesion between the aluminum or aluminum oxide vacuum coated surface and the barrier substrate.

[0080] In some embodiments, the resulting barrier layer has a viscosity of less than 10 cc / cm, measured at 50% relative humidity and 23° C. according to ASTM standard D-3985. 2 / 24h or less, preferably 5cc / cm 2 / 24h, preferably less than 1cc / cm 2 / Has an oxygen transmission rate (OTR) of less than 24h.

[0081] In some embodiments, the resulting barrier layer has a hardness of 10 g / m2, measured at 50% relative humidity and 23° C. according to ASTM standard F1249. 2 / 24h, preferably less than 5g / m 2 / 24h, more preferably less than 1g / m 2 / 24h water vapor transmission rate (WVTR) of less than.

[0082] In addition to providing good barrier properties against oxygen and water vapor, the barrier layer according to the present invention can also form a good barrier against other gases, as well as fragrances and odors.

[0083] According to a second aspect described herein, there is provided a method for producing a paper or paperboard based packaging laminate, the method comprising: i) providing a paper or paperboard substrate; and ii) providing a barrier layer produced according to the method according to the first aspect on a paper or paperboard substrate to obtain a paper or paperboard based packaging laminate. Includes.

[0084] Paper generally refers to a thin sheet-like material made from wood pulp or other fibrous substances containing cellulose fibers, and used for writing, drawing or printing on, or as a packaging material.

[0085] Paperboard is generally a strong, thick paper or cardboard containing cellulose fibers, used for boxes and other types of packaging. Paperboard may be bleached or unbleached, coated or uncoated, and may be manufactured in a variety of thicknesses, depending on the requirements of the final use. Paperboard may be a single-ply material, or a multi-ply material consisting of two or more plies. A common type of multi-ply board consists of a relatively low density mid-ply (sometimes called a "bulk ply") sandwiched between two outer plies of relatively high density. The relatively low density mid-ply is typically 750 kg / m 3 Density below 700 kg / m 3 Below 650kg / m 3 Below 600kg / m 3 Below 550kg / m 3 Below 500kg / m 3 Below 450kg / m 3 Below 400kg / m 3 or less than 350 kg / m 3 The denser outer plies will usually have a density at least 100 kg / m2 higher than the mid ply. 3 , preferably at least 200 kg / m2 denser than the mid-ply 3 ,expensive.

[0086] Paper or paperboard-based packaging laminates are packaging materials formed primarily from paperboard. The paper or paperboard substrate can be made from pulp (including pulp from virgin fibers), examples of which are mechanical, chemical and / or thermochemical pulps. The substrate can also be made from shredded or recycled paper. In addition to paper or paperboard, paper or paperboard-based packaging laminates can include additional layers or coatings designed to improve the performance and / or appearance of the packaging laminate.

[0087] Paper or paperboard based packaging laminates usually have a first outermost surface or printed side intended to be used as the outer surface and a second outermost surface intended to be used as the inner surface of the packaging container. The side of the paper or paperboard substrate comprising the barrier layer according to the invention is preferably intended to be used as the inner surface of the packaging container.

[0088] In some embodiments, the paper or paperboard substrate has a thickness of at least 100 g / m 2 In some embodiments, the paper or paperboard substrate has a basis weight of at least 150 g / m 2 , 200g / m 2 , 250g / m 2 , 300g / m 2 , 350g / m 2 , or 400 g / m 2 The paper or paperboard substrate preferably has a basis weight of 1000 g / m 2 , 800g / m 2 , or 600 g / m 2 Unless otherwise stated, basis weight is determined according to ISO standard 536.

[0089] In some embodiments, the paper or paperboard substrate has a viscosity of 700 kg / m 3 Density below 600 kg / m 3 Unless otherwise stated, density is determined according to ISO standard 534.

[0090] The paper or paperboard substrate can be a single-ply paperboard or a multi-ply paperboard. In some embodiments, the paper or paperboard substrate is a multi-ply paperboard. In some embodiments, the paper or paperboard substrate is a multi-ply paperboard consisting of two or more plies. In some embodiments, the paper or paperboard substrate is a multi-ply paperboard consisting of three or more plies. In some embodiments, the paper or paperboard substrate is a multi-ply paperboard consisting of a relatively low density mid-ply sandwiched between two relatively high density outer plies.

[0091] In some embodiments, the paper or paperboard substrate is a paperboard having a foam formed therein. In some embodiments, the paper or paperboard substrate is a multi-ply paperboard, at least one of the plies, preferably the mid-ply, has a foam formed therein.

[0092] The construction of the paper or paperboard based packaging laminate according to the invention allows for the use of a large amount of recycled fibers in the paper or paperboard substrate, since the barrier structure prevents the migration of mineral oil based compounds. Thus, in some embodiments, the paper or paperboard substrate comprises at least 5% by weight, preferably at least 10% by weight, of recycled fibers.

[0093] In some embodiments, the paper or paperboard substrate further comprises an inorganic coating layer on one or both of its major surfaces. In some embodiments, the inorganic coating layer has a composition, based on the dry weight of the inorganic coating layer, of: 50 to 95% by weight of fine inorganic particles, and Binder: 5-50% by weight include.

[0094] In some embodiments, the inorganic coating layer comprises 10 to 35 weight percent of the binder.

[0095] In some embodiments, the particulate mineral is selected from the group consisting of kaolin, calcium carbonate, bentonite, talc, and combinations thereof, preferably kaolin or calcium carbonate, and more preferably kaolin.

[0096] The binder may include a single binder or a combination of binders. The binder may preferably include a water-dispersible binder, or a water-soluble binder, or a combination thereof. In some embodiments, the water-dispersible binder includes a latex binder. In some embodiments, the water-soluble binder includes starch, PVOH, cellulose derivatives (e.g., CMC), proteins, or seaweed. An advantage of using a water-soluble binder is that recycling of the laminate becomes even easier.

[0097] In some embodiments, the basis weight of the inorganic coating layer is from 4 to 30 g / m 2 More preferably, the range is 6 to 14 g / m 2 is in the range.

[0098] The inorganic coating layer is preferably applied in at least two different coating steps with drying of the coated film between these steps. The inorganic coating layer may be calendered, preferably with a soft calender or a belt calender.

[0099] Providing a barrier layer according to the present invention onto a paper or paperboard substrate can be achieved in a number of different ways.

[0100] In some embodiments, the providing step ii) comprises laminating a free-standing barrier layer produced according to the first aspect to a paper or paperboard substrate.

[0101] In some embodiments, the providing step ii) comprises laminating a barrier layer comprising at least 50% by weight highly refined cellulose pulp (HRC), based on the dry weight of the barrier substrate, to a paper or paperboard substrate, and thereafter transferring a vacuum coating layer from a backing layer of a transfer coating substrate to the barrier substrate according to the first aspect.

[0102] Lamination of the barrier layer or barrier substrate to the paper or paperboard substrate can be accomplished by an adhesive tie layer applied between the barrier layer or substrate and the paper or paperboard substrate. The tie layer can be an adhesive layer applied by any suitable method known in the art. For example, the tie layer can be an adhesive layer applied by liquid coating methods known in the art, such as a solution or dispersion of the adhesive in an aqueous or organic carrier solvent, or the adhesive can be applied in molten form using extrusion coating, or in the form of a solid adhesive by lamination.

[0103] In some embodiments, the providing step ii) comprises coating the paper or paperboard substrate with a coating dispersion comprising at least 50% by weight, based on the dry weight of the coating dispersion, of highly refined cellulose pulp (HRC) and drying the coating dispersion to form a barrier substrate on the paper or paperboard substrate and thereafter transferring the vacuum coating layer from the backing layer to the barrier substrate according to the first aspect.

[0104] According to a third aspect described herein there is provided a barrier layer obtainable by a method according to the first aspect.

[0105] According to a fourth aspect described herein there is provided a paper or paperboard based packaging laminate obtainable by a method according to the second aspect.

[0106] The paper or paperboard based packaging laminates according to the invention can provide a more readily repulpable and recyclable alternative to conventional materials using layers of aluminum foil. In some embodiments, the paper or paperboard based packaging laminates have a reject rate according to PTS RH 021 / 97 of less than 30%, preferably less than 20%, more preferably less than 10%.

[0107] The paper or paperboard based packaging laminate may further be provided with an outermost polymer layer on one or both sides thereof. The outermost polymer layer preferably provides liquid barrier properties and mechanical protection for the paper or paperboard based packaging laminate surface. The outermost polymer layer is preferably also heat sealable.

[0108] In some embodiments, a paper or paperboard based packaging laminate comprises a first outermost polymer layer, preferably a polyethylene layer, disposed on a paper or paperboard substrate.

[0109] In some embodiments, the paper or paperboard based packaging laminate further comprises a second outermost polymer layer, preferably a polyethylene layer, disposed over the vacuum coating layer.

[0110] An outermost polymer layer may, of course, hinder repulping, but may still be necessary or desirable in some applications. Additional polymer layers may be applied, for example, by extrusion coating, film lamination, or dispersion coating.

[0111] The outermost polymer layer may comprise any of the thermoplastic polymers commonly used in protective and / or heat-sealable layers in paper or paperboard-based packaging laminates in general, or in liquid or food packaging cardboard in particular. Examples include polyethylene (PE), polyethylene terephthalate (PET), polyethylene furanoate (PEF), polypropylene (PP), polyhydroxyalkanoate (PHA), polylactic acid (PLA), polyglycolic acid (PGA), starch, and cellulose. Polyethylene, particularly low density polyethylene (LDPE) and high density polyethylene (HDPE), is the most common and versatile polymer in liquid or food packaging cardboard. The polymers used are preferably produced from renewable materials.

[0112] Thermoplastic polymers are useful because they can be conventionally manufactured by extrusion coating techniques to form very thin, uniform films with good liquid barrier properties. In some embodiments, the additional polymer layer comprises polypropylene or polyethylene. In a preferred embodiment, the outermost polymer layer comprises polyethylene, more preferably LDPE or HDPE.

[0113] In some embodiments, the outermost polymer layer is formed by extrusion coating the polymer onto the surface of a paper or paperboard substrate or laminate. Extrusion coating is a process in which a molten plastic material is applied to a substrate to form a very thin, smooth, uniform layer. The coating can be formed by the extruded plastic itself, or the molten plastic can be used as an adhesive to laminate a solid plastic film onto the substrate. Common plastic resins used in extrusion coating include polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET).

[0114] The basis weight of each outermost polymer layer is preferably 50 g / m 2Generally, the outermost polymer layer preferably has a thickness of at least 8 g / m2 to form a continuous, substantially defect-free film. 2 Preferably, a basis weight of at least 12 is required. In some embodiments, the basis weight of the outermost polymer layer is between 8 and 50 g / m 2 in the range of 12 to 50 g / m 2 is in the range.

[0115] Some examples of possible configurations for the barrier layer according to the invention in paper or paperboard based packaging laminates are given below: Polyolefin / Paperboard base material / Tie layer / Barrier layer / Polyolefin ·Paperboard base material / bonding layer / adhesive layer / barrier layer / polyolefin Polyolefin / Paperboard substrate / Inorganic coating / Tie layer / Barrier layer / Polyolefin ·Paperboard base material / bonding layer / barrier layer / polyolefin ·Paperboard base material / bonding layer / barrier layer / primer coating layer / polyolefin ·Ink receiving layer / paperboard / bonding layer / barrier layer / polyolefin.

[0116] While the products, polymers, materials, layers, and processes are generally described in terms of "comprising" various components or steps, the products, polymers, materials, layers, and processes may also "consist essentially of" or "consist of" the various components and steps.

[0117] While the invention has been described with reference to various exemplary embodiments, those skilled in the art will recognize that various changes can be made without departing from the scope of the invention and that equivalents can be substituted for these elements. In addition, many modifications may 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 not intended that the invention be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but the invention is intended to include all embodiments falling within the scope of the appended claims.

[0118] Working Example Example 1 (comparative example): Direct vacuum coating of packaging paper Wrapping paper base material with inorganic coating on one side (basis weight 80g / m 2 The physical properties of the paper substrate were as follows: Basis weight (ISO 536) 80g / m 2 , thickness (ISO 534) 80μm, tensile strength (ISO 1924-2 (MD)) 4.3kN / m, tear strength (ISO 1974 (CD)) 650mN, moisture content (ISO 638) 4.0%, Cobb60 (ISO 535, reverse) 25g / m 2 , Opacity (ISO 2471 (C / 2o)) 96%.

[0119] The barrier properties of the paper substrate before vacuum coating (OTR: measured according to ASTM standard D-3985 at 50% relative humidity and 23°C, and WVTR: measured according to ASTM standard F1249 at 50% relative humidity and 23°C) were out of range (no barrier properties). The paper substrate was primer coated with three thin layers of a PVOH-based solution, with a total coating weight of 4 g / m 2 After coating, the paper substrate was subjected to vacuum coating with Al2O3 to obtain a coating weight corresponding to an optical density of 3.5. After vacuum coating, the barrier properties (OTR and WVTR) were measured again. The OTR (23 / 50) was 512 cc / m 2 / 24h, WVTR is 0.19g / m 2 / 24h.

[0120] Example 2: Transfer coating onto packaging paper substrate In this case, the wrapping paper base material (90g / m2) is inorganically coated on one side. 2 The transfer coating was performed on the inorganic coated side using a 100% polyester resin. The physical properties of the wrapper paper substrate were as follows: Thickness (ISO 534): 90μm, Tensile strength (ISO 1924-2 (MD)): 4.6kN / m, Tear strength (ISO 1974 (CD)): 780mN, Moisture content (ISO 638): 4.0%, Cobb60 (ISO 535, reverse): 25g / m 2 , opacity ((ISO 2471 (C / 2o))97%.

[0121] For transfer coating, a transfer coated substrate was prepared by vacuum depositing a layer of AlOx onto a release layer coated onto a backing layer of PET film. A water-based polyurethane adhesive was applied onto the vacuum deposited layer and allowed to dry. The adhesive AlOx layer was then transferred to the surface of the paper substrate using dry lamination at elevated temperature and pressure. The backing layer was peeled off 24 hours after lamination.

[0122] Before transfer coating, the WVTR (ASTM F1249, 23 / 50) of the wrapping paper substrate was outside the range (no WVTR barrier). After transfer coating, the WVTR (ASTM F1249, 23 / 50) was 0.3 g / m 2 / 24h.

[0123] Example 3: Transfer coating on barrier substrates containing highly refined pulp Highly refined pulp containing 100% pulp (Schopper-Riegler (SR) number of approximately 95, as determined according to ISO standard 5267-1) was applied to a thin barrier substrate (32 g / m2) on a test paper machine. 2 ) was manufactured.

[0124] This barrier substrate was then subjected to transfer coating as described in Example 2.

[0125] After transfer coating, the barrier properties (OTR and WVTR) were measured. OTR (ASTM D-3985, 23 / 50) was 2.5 cc / m 2 / 24h, and the WVTR (ASTM F1249, 23 / 50) is 1.7g / m 2 / 24h, and both the OTR and WVTR were confirmed to be low after transfer coating of barrier substrates containing highly refined pulp.

[0126] Example 4: Transfer coating on a barrier substrate (PVOH coated) containing highly refined pulp A highly refined pulp containing approximately 80% pulp (SR approximately 95, determined according to ISO standard 5267-1) and 20% kraft pulp was mixed on a test paper machine with a thin barrier substrate (32 g / m 2 The OTR (ASTM D-3985, 23 / 50) of the uncoated substrate was >366 cc / m 2 / 24h, and WVTR (ASTM F1249, 23 / 50) is >38g / m 2 / 24h.

[0127] The barrier substrate was then primer coated with a PVOH-based solution to a total coating weight of approximately 2-4 g / m2. 2 It became.

[0128] This barrier substrate was then subjected to transfer coating as described in Example 2.

[0129] After transfer coating, the barrier properties (OTR and WVTR) were measured. OTR (ASTM D-3985, 23 / 50) was 0.3 cc / m 2 / 24h, and the WVTR (ASTM F1249, 23 / 50) is 0.6g / m 2 / 24h, and both the OTR and WVTR were confirmed to be low after transfer coating of barrier substrates containing highly refined pulp.

[0130] Example 5: Transfer metallization on barrier substrates containing fine MFC A fine MFC suspension was produced by fibrillation of enzyme-treated kraft pulp, and the MFC suspension was then applied to a barrier substrate (basis weight 30 g / m 2The OTR (ASTM D-3985, 23 / 50) of the uncoated substrate was 4.5 cc / m 2 / 24h, and the WVTR (ASTM F1249, 23 / 50) is 46g / m 2 / 24h.

[0131] This barrier substrate was then subjected to transfer coating as described in Example 2.

[0132] After transfer coating, the barrier properties (OTR and WVTR) were measured. OTR (ASTM D-3985, 23 / 50) was 0.4 cc / m 2 / 24h, and the WVTR (ASTM F1249, 23 / 50) is 0.4g / m 2 / 24h, and both the OTR and WVTR were confirmed to be low after transfer coating of the barrier substrate containing fine MFC.

Claims

1. 1. A method for producing a barrier layer for a paper or paperboard based packaging laminate, comprising: a) providing a barrier substrate comprising at least 50% by weight, based on the dry weight of the barrier substrate, of highly refined cellulose pulp (HRC), the HRC having a Shopper-Riegler (SR) number greater than 80, determined in accordance with ISO standard 5267-1; b) providing a transfer coating substrate comprising a vacuum coating layer and a backing layer separated by a release layer; and c) transferring the vacuum coating layer from the backing layer to the barrier substrate by a transfer coating process using an adhesive layer applied on the barrier substrate and / or the vacuum coating layer to obtain a barrier layer for a paper or paperboard based packaging laminate. A method comprising:

2. The method of claim 1 , wherein the barrier substrate is a free-standing barrier substrate film.

3. The method of claim 1 , wherein the barrier substrate is a coating layer on a paper or paperboard substrate.

4. The barrier substrate is 2 to 100 g / m ２ in the range of 2 to 60 g / m ２ More preferably, in the range of 2 to 50 g / m ２ The method according to any one of claims 1 to 3, wherein the base weight is in the range of

5. 5. The method of any one of claims 1 to 4, wherein the barrier substrate comprises at least 70%, preferably at least 90%, highly refined cellulose pulp, based on the dry weight of the barrier substrate.

6. 6. The method according to claim 1, wherein the highly refined cellulose pulp has a Shopper-Riegler (SR) number, determined according to ISO standard 5267-1, of greater than 85, preferably greater than 90.

7. 7. The method according to any one of claims 1 to 6, wherein the highly refined cellulose pulp is microfibrillated cellulose (MFC).

8. 8. The method according to any one of claims 1 to 7, wherein the barrier substrate has a Gurley Hill value, measured according to ISO standard 5636-5, of more than 5000 s / 100ml, preferably more than 20,000 s / 100ml, more preferably more than 42,300 s / 100ml.

9. 9. The method according to any one of the preceding claims, wherein the barrier substrate has a moisture content by weight, determined according to ISO 638, of at least 1.5%, preferably at least 2%, more preferably at least 3, or at least 3.5, or at least 4%.

10. The barrier substrate has a coating strength of 30 g / m2, measured according to ASTM standard F1249 at 50% relative humidity and 23°C. ２ 10. The method of claim 1, wherein the composition has a water vapor transmission rate (WVTR) of greater than 24 h.

11. The transfer coating process contacting and adhering the vacuum coating layer to the barrier substrate using an adhesive layer provided on the barrier substrate and / or the vacuum coating layer; and removing the backing layer, leaving the vacuum coating layer and, optionally, the release layer on the barrier substrate; The method of any one of claims 1 to 10, comprising:

12. 12. The method of any one of claims 1 to 11, wherein the vacuum coating layer, in contact with the barrier substrate via an adhesive layer, is subjected to pressure, heat and / or radiation to improve adhesion between the vacuum coating layer and the barrier substrate.

13. The method of claim 1 , wherein the backing layer comprises a plastic film.

14. 14. The method of any one of claims 1 to 13, wherein the release layer comprises a layer of material that adheres less to the backing layer or to the vacuum coating layer than the adhesive layer adheres to the barrier substrate layer and to the vacuum coating layer.

15. 15. The method of any one of claims 1 to 14, wherein the release layer comprises a layer of material that adheres less to the backing layer than it adheres to the vacuum coating layer, or to the backing layer, such that when the backing layer is removed, the entire release layer remains on the vacuum coating layer, or on the backing layer.

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

17. 17. The method of any one of claims 1 to 16, wherein the vacuum coating layer comprises an organic vacuum coating layer.

18. The method according to any one of the preceding claims, wherein the vacuum coating layer has a thickness in the range of 10 to 600 nm, preferably in the range of 10 to 250 nm, more preferably in the range of 50 to 250 nm.

19. 19. The method of any one of claims 1 to 18, wherein the adhesive layer comprises at least 50% by weight, on a dry weight basis, of an adhesive polymer or a mixture of adhesive polymers.

20. 20. The method of any one of claims 1 to 19, wherein the adhesive layer comprises one or more adhesive polymers selected from the group consisting of polyolefins, polyurethanes, and acrylic copolymers.

21. 21. The method of any one of claims 1 to 20, wherein the adhesive layer comprises at least 50% by weight, on a dry weight basis, of a water soluble polymer or mixture of water soluble polymers.

22. 22. The method according to claim 21, wherein the water soluble polymer is selected from the group consisting of polyvinyl alcohol (PVOH), carboxymethyl cellulose (CMC), starch, alginate and hemicellulose, preferably PVOH.

23. 23. The method according to claim 21 or 22, wherein the adhesive layer further comprises a cross-linking agent capable of cross-linking the water-soluble polymer, preferably an organic acid, more preferably citric acid.

24. 24. The method of any one of claims 21 to 23, wherein the adhesive layer further comprises up to 50% by weight, based on dry weight, of microfibrillated cellulose (MFC), nanocrystalline cellulose, chemically modified cellulose derivatives such as sodium carboxymethylcellulose, hydroxypropylcellulose, ethylhydroxyethylcellulose, cellulose acetate, hydroxyethylcellulose, hemicellulose, or combinations thereof.

25. The resulting barrier layer has a viscosity of 10 cc / cm2 as measured at 50% relative humidity and 23°C according to ASTM standard D-3985. ２ / 24h or less, preferably 5cc / cm ２ / 24h or less, more preferably 1cc / cm ２ 25. The method of claim 1 , wherein the composition has an oxygen transmission rate (OTR) of less than 1 / 24h.

26. The resulting barrier layer has a hardness of 10 g / m2, measured at 50% relative humidity and 23°C according to ASTM standard F1249. ２ / 24h or less, preferably 5g / m ２ / 24h or less, more preferably 1g / m ２ 26. The method of claim 1 , wherein the composition has a water vapor transmission rate (WVTR) of less than 1 / 24h.

27. 1. A method for producing a paper or paperboard based packaging laminate comprising the steps of: i) providing a paper or paperboard substrate; and ii) providing a barrier layer produced by the method according to any one of claims 1 to 26 on a paper or paperboard substrate to obtain a paper or paperboard based packaging laminate. A method comprising:

28. 28. The method of claim 27, wherein step ii) comprises laminating a free-standing barrier layer produced by the method of any one of claims 1 to 26 to a paper or paperboard substrate.

29. 28. The method of claim 27, wherein step ii) comprises laminating a barrier substrate comprising at least 50% by weight, based on the dry weight of the barrier substrate, of highly refined cellulose pulp (HRC) to a paper or paperboard substrate, and thereafter transferring the vacuum coating layer from the backing layer to the barrier substrate as defined in any one of claims 1 to 26.

30. 28. The method of claim 27, wherein step ii) comprises coating a paper or paperboard substrate with a coating dispersion comprising at least 50% by weight, based on the dry weight of the coating dispersion, of highly refined cellulose pulp (HRC) and drying the coating dispersion to form a barrier substrate on the paper or paperboard substrate and thereafter transferring the vacuum coating layer from the backing layer to the barrier substrate as defined in any one of claims 1 to 26.

31. A barrier layer obtainable by the method according to any one of claims 1 to 26.

32. A paper or paperboard based packaging laminate obtainable by the method according to any one of claims 27 to 30.

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