Laminated packaging materials and packaging containers including barrier-coated cellulosic substrates

Abstract

The present invention provides a sintering resistance of at least 900 kg / m 3 Density and 30~80g / m 2 and a barrier coated cellulosic substrate (10a; 25a) comprising a cellulosic substrate (11) having a basis weight of 100 g / m2 or less, the cellulosic substrate having at least one gas barrier coating (13a, 14a; 14b) applied to a first surface of the cellulosic substrate, the laminated packaging material being particularly intended for packaging oxygen sensitive products such as liquid carton food packaging, and a packaging container comprising the laminated packaging material.

Description

[Technical field]

[0001] The present invention relates to a laminated packaging material for oxygen sensitive products such as liquid carton food packages, a laminated packaging material comprising a barrier coated paper or cellulosic substrate for use as a barrier sheet of the laminated packaging material, and a packaging container comprising the laminated packaging material.The present invention further relates to a laminated packaging material comprising a barrier coated paper or cellulosic substrate obtained by applying at least one gas barrier coating of at least one gas barrier material to a total thickness of 2-5000 nm. [Background technology]

[0002] Single-use packages for liquid foods are often manufactured from paperboard or carton-based packaging laminates. One such commonly used package is sold under the trademark "Tetra Brik Aseptic" and is primarily employed for the aseptic packaging of liquid foods such as milk, fruit juices, etc., sold for long-term ambient storage. The packaging material of this known package is usually a laminate comprising a bulk or core layer of paper, paperboard or other cellulose-based material and a liquid-tight outer layer of thermoplastic. To make the package gas-tight, and in particular oxygen-tight, for the purposes of aseptic packaging or packaging of, for example, milk or fruit juice, these laminates usually comprise at least one additional layer, most commonly aluminum foil.

[0003] On the inside of the laminate, i.e. the side intended to face the filled food contents of the container produced from the laminate, there is an innermost layer applied onto the aluminum foil, which comprises one or more partial layers comprising adhesive polymers and / or heat-sealable thermoplastic polymers such as polyolefins, and, outside the bulk layer, there is an outermost heat-sealable polymer layer.

[0004] Packaging containers are generally produced by modern high-speed packaging machines of the type that form, fill and seal packages from webs of packaging material or prefabricated blanks. The packaging containers are produced by joining the longitudinal edges of a web of laminate packaging material together at overlap joints by welding together the inner and outer heat-sealable thermoplastic polymer layers, converting it into a tube. The tube is filled with the desired liquid food product and then divided into individual packages by repeatedly transversely sealing the tube at a predetermined distance from each other below the level of the contents in the tube. The packages are separated from the tube by scoring along the transverse seals and formed into the desired geometric shape, usually a parallelepiped, by creating folds in the packaging material along pre-prepared crease lines.

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

[0006] Packaging containers for sensitive liquid foods, such as milk and juice, can also be produced from sheet blanks or preassembled blanks of the laminate packaging material of the invention. Packages are produced from flat-folded tubular blanks of the packaging laminate by first assembling the blanks to form an open tubular container capsule, one open end of which is closed by folding and heat sealing an integral end panel. The container capsule thus closed is filled from the other open end with a food product, such as juice, and is then closed by further folding and heat sealing the corresponding integral end panel. Examples of packaging containers produced from sheet and tubular blanks are the conventional so-called gable top packages. Packages of this type can also be provided with a molded plastic top and / or a screw cap.

[0007] The aluminum foil layer of the packaging laminate provides gas barrier properties that are significantly superior to other gas barrier materials. Conventional aluminum foil-based packaging laminates for aseptic packaging of liquid foods are the most cost-effective packaging materials available on the market today for their performance levels.

[0008] Other materials that compete with foil-based materials need to be cost effective in terms of raw materials, have comparable food preservation properties, and require relatively low complexity in converting the material into the finished packaging laminate.

[0009] Among the efforts to develop non-aluminum foil materials for liquid food carton packaging, there is also a general drive to develop prefabricated films or sheets with high or multiple barrier properties that can replace aluminum foil barrier materials in traditional laminate packaging materials, or combine multiple separate barrier layers in laminate materials and be compatible with traditional processes for lamination and manufacturing.

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

[0011] Patent publication WO2011 / 003565A1 discloses a non-aluminium foil packaging material comprising a pre-coated metallized paper or cellulosic substrate intended for induction heat sealing.

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

[0013] However, there remains a need to further improve the oxygen gas barrier properties of prior art gas barrier coated paper substrates, and there is also an increasing need to improve the recyclability and environmental sustainability properties of materials used in gas barrier coated paper substrates and laminated packaging materials containing same. Summary of the Invention [Problem to be solved by the invention]

[0014] It is an object of the present invention to provide an improved barrier coated cellulosic substrate for lamination to packaging materials.

[0015] It is also an object of the present invention to use a barrier coated paper or cellulosic substrate that has good gas barrier properties and offers improved recyclability and environmental sustainability to meet the needs of future sustainable laminate packaging materials.

[0016] It is a further general object of the present invention to provide a laminate packaging material for oxygen sensitive products, such as a non-foil laminate packaging material for liquid, semi-liquid or moist food products, that does not contain aluminum foil and provides good gas and other barrier properties suitable for long term aseptic packaging at a reasonable cost.

[0017] A particular objective is to provide a package that has good gas and water vapour barrier properties, as well as a recyclability and sustainable environmental profile compared to aluminium foil barrier materials, and to provide a cost-effective, foil-free, paper or paperboard based laminate packaging material for the purpose of producing packages for long term aseptic food storage.

[0018] These objectives are therefore attainable according to the present invention by laminated packaging materials and packaging containers as defined in the appended claims, comprising a barrier-coated cellulosic substrate as defined and described herein or obtained by the process for producing a barrier-coated cellulosic substrate as described herein. [Means for solving the problem]

[0019] A barrier coated cellulosic substrate is provided for use as a barrier sheet in a laminate packaging material for oxygen sensitive products, the barrier coated cellulosic substrate having a barrier strength of at least 900 kg / m 3 Density and 30~80g / m 2and applying to a first side of the cellulosic substrate at least one gas barrier coating of at least one gas barrier material to a total thickness of from 2 to 7000 nm, for example from 2 to 5000 nm, for example from 2 to 4000 nm, the barrier coated cellulosic substrate further comprising a ductile base layer pre-coating applied onto a surface of the first side of the cellulosic substrate by dispersion coating and subsequent drying and disposed beneath the at least one gas barrier coating, such that the barrier coated cellulosic substrate is suitable for providing gas barrier properties to laminate packaging materials and packages using same.

[0020] The gas barrier coating may be a barrier dispersion coating applied by dispersion or solution coating, and / or a barrier deposition coating applied by a deposition method.

[0021] The barrier dispersion coating may comprise a polymer selected from the group consisting of vinyl alcohol polymers and copolymers, such as polyvinyl alcohol, PVOH, and ethylene vinyl alcohol, EVOH, starch and starch derivatives, xylan, xylan derivatives, nanofibril cellulose / microfibril cellulose, NFC / MFC, nanocrystalline cellulose, NCC, and blends of two or more thereof.

[0022] The barrier deposition coating may alternatively or additionally comprise a deposition coating of a material selected from a metal, a metal oxide, an inorganic oxide and a carbon coating. The barrier deposition coating may be a deposition coating selected from the group consisting of an aluminum deposition coating and an aluminum oxide (AlOx), preferably an aluminum metallized coating.

[0023] The at least one gas barrier coating may comprise a barrier dispersion coating first applied by dispersion coating or solution coating onto a ductile base layer pre-coating and a barrier deposition coating subsequently applied by a deposition method onto the barrier dispersion coating.

[0024] The ductile base layer pre-coating may be made from an aqueous composition comprising a polymeric binder material having inherent ductile properties selected from the group consisting of other latexes of acrylate polymers and copolymers, such as styrene-butadiene copolymer (SB) latex, styrene-acrylate copolymer (SA) latex, vinyl acrylate copolymer latex and vinyl acetate-acrylate copolymer latex, and bio-based polymeric materials.

[0025] The pre-coating of the ductile base layer may advantageously further comprise a filler material to further smooth the surface of the cellulosic substrate. The filler may be an inorganic material and in a preferred embodiment comprises layered particles of inorganic compounds. Such layered fillers may further contribute to the barrier properties of the material by producing overlapping mineral flakes or lamellae, preventing the migration of small molecules through the material. Such layered inorganic particles may be clays such as kaolin clay or bentonite clay, silicates and talcum particles.

[0026] Ductile base layer pre-coating with a dry weight of 2-15g / m 2 , for example 5 to 15 g / m 2 , for example 8 to 15 g / m 2 , for example 10 to 15 g / m 2 It may be applied by aqueous dispersion coating in an amount of

[0027] The cellulosic substrate may further have a second ductile coating on an opposing side thereof, which may be of the same type as the ductile base layer pre-coating on the first side of the substrate.

[0028] According to a first aspect of the present invention, there is provided a laminate packaging material comprising a barrier coated cellulosic substrate as described herein. The laminate packaging material may further comprise a first outermost protective material layer and a second innermost liquid-tight material layer. The second innermost liquid-tight material layer forms a contact layer towards a product to be packaged in a packaging container formed from the laminate packaging material and may be heat-sealable to itself or to another thermoplastic material.

[0029] The laminate packaging material may further include additional layers of paper, paperboard, or other cellulosic material that constitute the bulk layer.

[0030] For the purpose of carton packaging of oxygen sensitive foods, such as liquid, semi-liquid or moist foods, the laminate packaging material comprises a bulk layer of paper, paperboard or other cellulosic material, a first outermost protective and / or liquid-tight layer of material, a second innermost liquid-tight and optionally heat-sealable layer of material, and a barrier-coated cellulosic substrate as described herein disposed inside the bulk layer and between the bulk layer and the second innermost layer.

[0031] In a second aspect of the present invention, there is provided a packaging container comprising the laminate packaging material of the first aspect. In one embodiment, the packaging container is intended for packaging liquid, semi-liquid or moist foods. According to one embodiment, the packaging container is at least partially manufactured from the laminate packaging material, and according to a further embodiment, is entirely manufactured from the laminate packaging material.

[0032] A method for producing the described barrier coated cellulosic substrate is provided, comprising a first step of providing a cellulosic substrate having a first side and a second side as a moving web in a roll-to-roll system, a second step of applying a first aqueous dispersion of a ductile base layer precoating composition onto the first side of the moving cellulosic substrate and optionally applying a second aqueous dispersion of a ductile coating composition to the other side of the moving substrate, followed by drying the applied ductile base layer precoating and optional second ductile coating composition by forced evaporation, and calendering the precoated and dried cellulosic substrate to a coating weight of at least 900 kg / m. 3 , e.g. at least 1000 kg / m 3 and a fourth step of applying a gas barrier coating by dispersion coating a second aqueous dispersion or solution of a barrier composition onto the moving cellulosic substrate and the first side of the ductile base layer pre-coating, followed by drying the barrier dispersion coating applied to the moving cellulosic substrate and the first side of the ductile base layer pre-coating by forced evaporation and / or barrier deposition coating to a total gas barrier coating thickness of 2 to 7000 nm, e.g., 2 to 5000 nm.

[0033] A fourth step of the method may comprise a first operation of applying a gas barrier coating by dispersion coating a second dispersion or solution of a barrier composition onto a first side of the transferred cellulosic substrate having the ductile base layer pre-coating and drying the applied gas barrier coating by forced evaporation, followed by a second operation of depositing a barrier deposition coating onto the first side of the transferred cellulosic substrate having the ductile base layer pre-coating and the gas barrier coating of the first operation.

[0034] In the past, it was believed that improved gas barrier properties from barrier-coated paper could be achieved by sourcing a better cellulosic substrate that would intrinsically provide gas barrier properties when further laminated to any polymeric layer, and / or by applying a thicker coating of a barrier coating material that has intrinsic gas barrier properties. However, it has recently become better understood that the interface between the barrier coating material and the cellulosic substrate is the area that contributes most to gas barrier properties and may play a key role for optimal performance of subsequently applied coatings. It has been found that optimal performance can be obtained by adding a ductile base layer precoat to the surface of the cellulosic substrate. In this way, the high density cellulosic substrate itself does not need to have as high a barrier property, and the amount of gas barrier polymer coated as a barrier precoat can be reduced. Thus, the use of a ductile base layer precoat improves gas barrier properties in packaging laminates, even though it does not contribute to gas barrier properties itself. The ductile base layer precoat composition should be selected to provide a ductile foundation while at the same time providing a uniform, dense, and conformable precoat surface to receive further gas barrier coatings. However, the material selected for the ductile base layer precoat does not need to have inherent gas barrier properties.

[0035] The ductile base layer pre-coating material is advantageously applied in the form of an aqueous composition comprising a polymeric binder material having inherent ductile properties selected from the group consisting of acrylate polymers and other latexes of copolymers, such as styrene-butadiene copolymer (SB) latex, styrene-acrylate copolymer (SA) latex, vinyl acrylate copolymer latex and vinyl acetate-acrylate copolymer latex, and bio-based polymeric materials. The first aqueous dispersion of the ductile base layer pre-coating composition may further comprise inorganic particles or pigments, such as clay, and / or fillers, such as cellulose fibrils.

[0036] The barrier coated cellulosic substrates obtained by the methods and coating layer configurations described above can provide improved gas barrier properties to laminate packaging materials and packaging containers made therefrom, and can also improve the recyclability and sustainability profiles of such packaging materials and packaging containers.

[0037] (Detailed Description) The term "long-term storage" as used in the context of the present invention means that the packaging container is capable of preserving the quality, i.e. nutritional value, hygienic safety and taste, of the packaged food at ambient temperature conditions for at least 1 or 2 months, such as at least 3 months, preferably 6 months, such as 12 months or more.

[0038] The term "package integrity" generally refers to the tightness of the package, i.e., the resistance of the packaging container to leakage or breakage. The term encompasses the resistance of the package to the ingress of bacteria, dirt, and other microorganisms that may deteriorate the food contained therein and shorten the expected shelf life of the package.

[0039] One major contribution to the package integrity of laminate packaging materials comes from good internal adhesion between adjacent layers of the laminate material. Another contribution comes from the resistance of the material to defects such as pinholes, breaks, etc. of each material layer, and yet another contribution comes from the strength of the seal joints where the material is sealed when forming the package. Thus, with respect to the integrity of the laminate packaging material itself, attention is focused on the adhesion of each laminate layer to its adjacent layers, and the ability of each material layer to withstand thermal and mechanical loads, for example, when folding and sealing to form the package. With respect to the sealing of the package, integrity is primarily focused on the quality of the seal joints, which is ensured by a well-functioning and robust sealing operation in the filling machine, which is further ensured by the properly adapted heat-sealing properties of the laminate packaging material.

[0040] The term "liquid or semi-liquid food" generally refers to food with a flowable content that may optionally contain food particles. Dairy and milk, soy, rice, grain and seed drinks, juice, nectar, soft drinks, water, flavored water, energy drinks, sports drinks, coffee or tea drinks, coconut water, wine, soup, jalapeno, tomato, sauces (such as pasta sauce), soy and olive oil are some non-limiting examples of foods that are contemplated.

[0041] Further examples of other oxygen-sensitive foods that can be packaged and protected with the laminate packaging material of the present disclosure are dry foods and / or fatty foods, such as, for example, milk powder and other powdered foods. Examples of fatty foods include cheese, butter, spreads, and the like. Such packaging may be, for example, flow-wrap packaging in bags or form, fill, seal (FFS) packaging. It may also be packaging in jars, trays, spread containers with lids, collapsible tubes, clamshell packages, sleeves, envelopes, or wrappers. In these applications, the packaging material is typically subjected to folding or similar types of stress (e.g., creases, stretches), making the barrier-coated cellulosic substrate-based packaging material of the present disclosure particularly suitable.

[0042] The term "sterile" in relation to packaging materials and containers refers to a state in which microorganisms have been removed, inactivated, or killed. Examples of microorganisms include bacteria and spores. Generally, when a product is filled aseptically into a packaging container, an aseptic process is used. In order to maintain the sterility during the shelf life of the packaging container, the integrity properties of the package are very important. For the long-term storage of the filled food, and also to preserve the original taste and nutritional value, e.g., vitamin C content, it is important to have a barrier property against gases such as oxygen gas and vapors.

[0043] The term "bulk layer" usually refers to the thickest layer or layer containing the most material in a multi-layer laminate, i.e., the layer that contributes most to the mechanical properties and dimensional stability of the laminate and the packaging container folded from the laminate, e.g., paperboard, carton, etc. It can also refer to the layer that provides a larger thickness distance in a sandwich structure that further interacts with stabilizing facing layers having a higher Young's modulus on either side of the bulk layer to achieve sufficient mechanical properties of the formed packaging container.

[0044] In this specification, the term "dispersion coating" refers to a coating technique in which an aqueous or substantially aqueous dispersion, suspension, emulsion or solution of a polymer is applied, usually in the form of a continuous web, to the surface of a substrate layer to form a solid, substantially non-porous coating after drying. The term "dispersion" therefore also includes any suspension, emulsion, solution or mixture thereof that is capable of providing such a coating after drying. Polyvinyl alcohol (PVOH, PVAL) is a typical polymer suitable for dispersion coating, but in practice, for example, at high saponification levels, it may rather be a polymer solution or a mixture of dispersed and dissolved PVOH. Dispersion-coated barrier layers or coatings are formed by dispersion coating techniques also called "liquid-film coating". The aqueous dispersion may comprise fine polymer particles and thus may be a latex.

[0045] As used herein, the term "latex" refers to a composition comprising an aqueous suspension or dispersion or emulsion of polymer particles, where these polymers are natural polymers, synthetic polymers, synthetic polymers derived from biomass, or combinations thereof.

[0046] The paper weight is measured in g / m according to the official ISO 536:2019 test method. 2 The thickness and density are measured in μm(m) and kg / m respectively according to ISO 534:2011. 3 It is measured in units.

[0047] The thickness of the polymer layer coated on the paper may be measured and estimated by taking sliced ​​cross-sectional samples of the structure and examining them under a microscope. Slicing may be performed, for example, using a cryomicrotome.

[0048] OTR was measured using a coulometric sensor-based Oxtran 2 / 21 (Mocon) instrument according to ASTM F1927-14 and ASTM F1307-14. See further description of the OTR test method in connection with the examples.

[0049] The method for measuring the OTR of flat materials specifies the amount of oxygen passing through the material per surface and unit time during a 24-hour period at a given temperature and atmospheric pressure, i.e., 21% oxygen (unless otherwise specified). The method for measuring the OTR of packaging materials specifies the amount of oxygen entering the packaging material per unit time during a 24-hour period at a given temperature and atmospheric pressure, i.e., 21% oxygen (unless otherwise specified).

[0050] Water vapor transmission rate (WVTR) measurements were performed at 38°C with a 90% driving relative humidity gradient by a Permatran 3 / 33 (Mocon) instrument (standard: ASTM F1249-13, using a modulated infrared sensor for relative humidity detection and WVTR measurement).

[0051] Surface roughness was measured according to TAPPI 555 om-15, which is the same as ISO 8791-4. For the purposes of the present invention, cellulosic substrates suitable for application of a barrier coating are not limited to a specific type of paper, but also include other cellulosic substrates based on natural cellulose, fibrous cellulose or micro / nanofibrillar cellulose of various degrees of crystallinity. However, the present invention does not apply to substrates made from plastics or polymers, such as films made from regenerated, i.e. dissolved and then precipitated, chemically modified cellulose polymers.

[0052] It has been found that the combination of a base layer pre-coating and a gas barrier coating according to the present invention has the potential to improve the gas barrier properties of paper substrates beyond what was previously thought possible.

[0053] To be suitable for the final barrier coating step by the vapor deposition coating process, the fibrous portion of the substrate must be no more than 60 g / m for reasons of efficiency and production economics, and to avoid blistering of the coating due to air entrapment in the fibrous cellulosic portion of the substrate. 2 Below, for example, 50 g / m 2 Less than 45 g / m 2 On the other hand, the cellulose-based substrate is 30 g / m or less. 2 Thinner or lower basis weights, when coated with a wet dispersion and then dried, may become too mechanically weak and / or have poor dimensional stability, which may result in shrinkage and curl problems and even web breaks. 2 , for example 30 to 65 g / m 2 , for example 35-60g / m 2 , for example 35 to 55 g / m 2 , for example 35-50g / m 2 It is more preferred to use a cellulosic substrate having a basis weight of

[0054] Further, the precoated cellulosic substrate has a coating strength of at least 900 kg / m 3The barrier coated cellulosic substrate should have a high density of 0.1 to 1.0 mm and a dense, smooth surface for the best interface with the gas barrier coating applied thereon. Thus, the barrier coated cellulosic substrate is desirably a precoated, calendered, e.g., super-precoated, calendered paper. Calendering or super-calendering, in addition to densifying the substrate, provides improved adhesion, or "integration," between the precoat layer and the paper substrate surface.

[0055] Cellulosic substrates for use in accordance with the present invention may be formed from cellulose fibers that contain at least 50% by dry weight of a chemical pulp, such as sulfate pulp, which is used to provide toughness to the paper for use in high speed coating and converting processes and in the final packaging.

[0056] Sulfate or "kraft" pulp can be advantageous for improved repulping in recycling and for general dewatering of the fibers.

[0057] For recycling and good dewatering ability, the cellulosic based fibres should have a Canadian Standard Freeness (CSF) higher than 300 ml, such as higher than 350 ml, such as higher than 400 ml, as measured by ISO 5267-2:2001. Correspondingly, the cellulosic based fibres should have a Shopper-Riegler value lower than 40°SR, such as lower than 36°SR, such as lower than 32°SR, as measured according to ISO 5267-1:1999.

[0058] The softwood pulp provides strength / toughness properties to the resulting paper and may comprise at least 50 wt% of the pulp. Preferably, thus the cellulosic substrate comprises at least 50 wt%, such as 60-100 wt%, for example 70-100 wt%, kraft softwood cellulose, such as bleached kraft softwood cellulose.

[0059] In some applications, such as liquid-tight packaging of wet, liquid, or viscous flowing products, it has been found to be advantageous to use cellulosic substrates that are as thin as possible, as this may require less polymer in adjacent layers.

[0060] To obtain optimal barrier properties with a minimum of barrier material, gas barrier coatings applied to paper and cellulosic substrates to thicknesses of a few micrometers or nanometers require that the substrate be first precoated with a ductile base layer.

[0061] The ductile base layer pre-coating may be derived from an aqueous composition comprising a polymeric binder material having inherent ductile properties selected from the group consisting of other latexes of acrylate polymers and copolymers, such as styrene-butadiene copolymer (SB) latex, styrene-acrylate copolymer (SA) latex, vinyl acrylate copolymer latex and vinyl acetate-acrylate copolymer latex, and bio-based polymeric materials.

[0062] The ductile base layer pre-coating can be derived from an aqueous composition comprising a bio-based polymeric binder material having inherent ductile properties selected from the group consisting of starch derivatives, polyisoprene, lignin-based polymers, alginates, gums, and soy-based proteins, and one or more latexes of such bio-based polymeric binder materials.

[0063] The ductile base layer precoating may further include a filler.

[0064] The ductile base layer pre-coating can be applied by any suitable dispersion coating technique, such as blade coating, rod coating, bar coating, smooth roll coating, reverse roll coating, lip coating, air knife coating, curtain flow coating, dip coating, slot-bonded layer coating techniques, followed by evaporation of the dispersion medium (usually water) by forced convection drying. Preferably, the ductile base layer pre-coating is applied by blade or rod coating techniques, followed by drying. The term "aqueous dispersion coating" includes coatings of aqueous compositions of polymer emulsions, dispersions, suspensions, solutions, and latex formulations, and also includes cases where such compositions further include pigments, inorganic particles, or other fillers.

[0065] The ductile base layer precoating may be derived from a water-based latex composition, such as a latex selected from the group consisting of styrene-butadiene latex (SB-latex), methylstyrene-butadiene latex, styrene-acrylate latex (SA-latex), acrylate latexes such as vinyl acrylate copolymers and vinyl acetate-acrylate latexes, styrene-butadiene-acrylonitrile latex, styrene-acrylate-acrylonitrile latex, styrene-butadiene-acrylate-acrylonitrile latex, styrene-maleic anhydride latex, styrene-acrylate-maleic anhydride latex, mixtures thereof, or bio-based latexes made from plant-derived polymeric materials. Additionally, styrene-acrylate and styrene-butadiene based latexes may be at least partially derived from biomass to achieve similar performance with an improved carbon footprint.

[0066] The ductile base layer precoating may be produced from a substantially plant-based source by producing an aqueous latex composition comprising an emulsion of a bio-based polymeric binder material, such as, in one embodiment, selected from the group consisting of starch derivatives, modified starches and crosslinked starches. The latex composition may be selected from the group consisting of polyisoprene, lignin-based polymers, alginates, gums such as guar gum, and soy-based proteins, including Ecosynthetix's "Ecosphere", Vystar's "Vytex", Stora Enso's "NeoLigno", Organoclick's "OC-Binder", and Polygal's "Polygal" surface coatings. Ecosynthetix's biolatex composition Ecosphere®, for example, is an aqueous latex of crosslinked starch particles. The latex may be produced by aqueous emulsion polymerization. Alternatively, as in the case of making a latex from a biopolymer, a biopolymer material such as starch may be plasticized under shear to a suitable particle size and then crosslinked by adding a crosslinking agent, after which the biopolymer particles may be added to an aqueous dispersion to form an aqueous latex or suspension of particles.

[0067] The ductile base layer precoating composition, in one embodiment, is made from a plant-derived or bio-based polymer and may be applied in the form of an aqueous latex of such polymer.

[0068] The ductile base layer pre-coating may be made from an aqueous latex composition comprising a polymeric material having inherent ductile properties selected from the group consisting of styrene-butadiene copolymers (SB), styrene-acrylate copolymers (SA), other acrylate polymers and copolymers such as acrylic vinyl copolymers and vinyl acetate acrylate copolymers, and aqueous latexes of bio-based polymeric materials.

[0069] In a further embodiment, the ductile base layer pre-coating may be made from an aqueous latex composition comprising a bio-based polymeric material having inherent ductile properties selected from the group consisting of starch derivatives including modified starches and crosslinked starches, polyisoprene, lignin-based polymers, alginates, gums, and soy-based proteins.

[0070] In a further embodiment, the ductile base layer pre-coating may be made from an aqueous latex composition that includes crosslinked starch particles.

[0071] The latex composition may further comprise inorganic filler particles such as, for example, kaolin clay or other layered clay compounds, silica particles, talcum particles and / or calcium carbonate, at 1-80% by weight of the dry content, such as 1-70% by weight, for example 1-50% by weight, such as 1-40% by weight, for example 30% by weight, for example 1-20% by weight. The inclusion of particles further supports ductility and at the same time provides sufficient flexibility to reduce tension in the precoating so that it can conform to the cellulose-based portions of the substrate when folded without cracking the precoating itself.

[0072] The latex composition may alternatively, or in addition, include an organic filler, such as microfibrillated cellulose.

[0073] In one embodiment, the ductile base layer pre-coating may comprise 4-45 wt%, such as 4-35 wt%, for example 4-25 wt%, such as 4-20 wt%, for example 4-16 wt% of a polymeric binder material having inherent ductile properties, and 55-96 wt%, such as 65-96 wt%, for example 75-96 wt%, for example 80-96 wt% of a filler, by dry weight, and optionally additional compounds such as thickeners and crosslinking compounds, such additions comprising up to 10 wt% of the ductile base layer pre-coating, based on dry weight.

[0074] In another embodiment, the ductile base layer precoating may comprise, on a dry weight basis, 10-20 wt. % of a polymeric binder material having inherent ductile properties, 75-85 wt. % of an inorganic filler, 3-5 wt. % of a crosslinking compound such as starch, and 1-2 wt. % of a thickening agent.

[0075] The filler may be an inorganic filler selected from the group consisting of clays such as bentonite clay, kaolin clay, talcum, CaCO3, and nanoclays including silica particles.

[0076] Preferably, the filler is an inorganic layered compound such as bentonite clay or kaolin clay.Specifically suitable such layered clay minerals are laponite, kaolinite, dickite, nacrite, halloysite, antigorite, chrysotile, pyrophyllite, montmorillonite, hectorite, saponite, sauconite, sodium tetrasilicic mica, sodium taeniolite, common mica, margarite, vermiculite, phlogopite, xanthophyllite, etc.A particular type of such nanoclay layered particles is the particle of montmorillonite, for example sodium-exchanged montmorillonite (Na-MMT).

[0077] The ash content of the cellulosic substrate thus precoated may be 15-25 wt%, for example 15-23 wt%, as determined by ISO 1762: 2019. The same range of ash content applies to gas barrier coated and precoated cellulosic substrates, i.e. 15-25 wt%.

[0078] The ductile base layer precoat composition has a dry weight of 2 to 15 g / m 2 , for example 5 to 15 g / m 2 , for example 8 to 15 g / m 2 , for example 10 to 15 g / m 2 It may be applied at a basis weight of

[0079] The polymer of the ductile base layer precoating may be selected to exhibit a glass transition temperature of -30 to +30°C, for example -30 to +20°C, to impart inherent ductility to a paper substrate coated with the base layer precoating.

[0080] The cellulosic substrate may further have a second ductile coating on an opposing side thereof, which may be of the same type as the ductile base layer pre-coating on the first side of the substrate.

[0081] The second ductile coating composition is applied by aqueous dispersion coating at a dry weight of 1 to 10 g / m 2 , for example 1 to 7 g / m 2 , for example 1 to 6 g / m 2 , for example 1 to 5 g / m 2 , for example 2 to 5 g / m 2 The latex composition may be applied in an amount of 0.1 to 1.0 wt. %. Particularly suitable latex compositions can be described as having a latex polymer chemical composition of styrene-butadiene copolymer or styrene-acrylic copolymer. Such latex polymers are miscible in water in all proportions. Another particularly suitable latex polymer may be an anionic aqueous dispersion of a copolymer of n-butyl acrylate and styrene.

[0082] The ductile base layer precoating should be coated directly adjacent to the surface of the paper or cellulosic substrate. The paper allows moisture to migrate outward through the laminate packaging material, and the ductile base layer precoating material may also allow such water vapor migration to prevent moisture from being undesirably trapped near the moisture sensitive barrier coating, such as PVOH or EVOH. Moisture that migrates through the material from the liquid food in the package is slowly transported through the paper and paperboard bulk layers of the laminate packaging material toward the outside of the package. The cellulosic substrate and paperboard bulk layers "breathe" the moisture from the barrier precoating, allowing the moisture content in the gas barrier coating to remain substantially constant over time.

[0083] The ductile base layer precoating may be coated onto the cellulosic substrate, forced convection dried, and then calendered. Calendering further integrates the ductile base layer precoating with the cellulosic surface of the substrate, improving surface bonding while at the same time creating a smooth surface for the ductile base layer precoating. The calendering may be a supercalendering process including multiple high pressure roller nips and at least one heated roller nip, for example four or more high pressure roller nips, in which case the density of the precoated cellulosic substrate is at least 900 kg / m 3 , e.g. 1000kg / m 3 More than 1100kg / m 3 The temperature of the thermo roller may be 100 to 300°C, for example, providing a surface temperature of 100 to 240°C.

[0084] The solids content in the applied aqueous latex coating may be in the range 45-70wt%, such as 45-60wt%, for example 47-55wt%, such as 48-51wt%.

[0085] The most suitable type of system for dispersion coating of ductile precoat or coating compositions is a blade coater or rod coater, where a large amount of coating composition is applied to the paper and the excess is scraped off again. The coating composition is applied onto the substrate by an applicator. Common applicators are jet applicators, roll applicators, and short dwell time applicators (SDTA). The advantage of roll applicators is that poor formation of the substrate paper is not important for them, and therefore they are suitable when thick coatings are desired. The blades used to scrape off the excess amount of coating are made of steel and may have ceramic tips to increase their lifespan. The applied coating is passed through a dryer, usually an IR dryer, hot air dryer, or cylinder dryer.

[0086] The basis weight of the ductile precoated cellulosic substrate is, in one embodiment, 40 to 80 g / m 2 , for example 40 to 75 g / m 2 , for example 40 to 70 g / m 2 , for example 40 to 65 g / m 2 may be also possible.

[0087] The thickness of the ductile pre-coated cellulosic substrate may be from 35 to 70 μm, such as from 35 to 65 μm, such as from 40 to 60 μm, such as from 45 to 60 μm.

[0088] The first, top surface of the ductile pre-coated cellulosic substrate can exhibit very low porosity.

[0089] The ductile base layer precoating may be applied as an aqueous latex composition having a solids content of 48-51 wt %, a Brookfield viscosity of 100-1000 mPa·s, and a pH of 5.5-8.

[0090] The ductile base layer precoating further comprises, as an aqueous composition, a dry weight of 5 to 15 g / m 2 It may also be applied by blade or rod coating.

[0091] The thus obtained precoated and dried cellulosic substrate may then be supercalendered at a calender nip pressure of at least 100 kN, such as at least 200 kN, such as 300 kN or more, and at a thermo roller surface temperature of 100-300° C., such as 100-240° C., such as 150-240° C. The cellulosic substrate including the ductile base layer precoating may be calendered to an air permeability below 100 nm / (Pa·s), which is the lower limit of the range in which the test method ISO 5636-5:2013 is applicable, and even to an air permeability value below 1 nm, such as 40-900 pm / (Pa·s), for example 40-800 pm / (Pa·s), for example 100-700 pm / (Pa·s), for example 200-500 pm / (Pa·s). The extremely dense surface provided by the ductile precoat base layer on high density cellulosic substrates is believed to enhance the robustness of the gas barrier when subsequently coated with a thin gas barrier coating.

[0092] The ductile precoated cellulosic substrate may have a first, upper surface surface roughness, measured according to SS-ISO 8791-2:2013, less than 100 ml / min Bendtsen, such as less than 80 ml / min Bendtsen, such as less than 50 ml / min Bendtsen, such as less than 30 ml / min Bendtsen, such as less than 20 ml / min Bendtsen.

[0093] Another measure of surface roughness is the Parker Printed Surface (PPS) roughness measured according to TAPPI 555 om-15, which is the same as ISO 8791-4.

[0094] The PPS roughness of the first upper ductile precoated cellulosic substrate surface is preferably 3.0 μm or less, such as 2.8 μm or less, such as 2.5 μm or less, such as 2.2 μm or less, such as 2.0 μm or less, such as 1.8 μm or less, as determined by the above test method, to further improve the gas barrier coating performance.

[0095] The cellulosic substrate comprising the ductile base layer precoating and at least one gas barrier coating may have a PPS surface roughness of 3.0 μm or less, 2.8 μm or less, 2.5 μm or less, 2.2 μm or less, 2.0 μm or less, 1.8 μm or less, etc., measured according to TAPPI 555 om-15, which is the same as ISO 8791-44.

[0096] The density of the ductile pre-coated cellulosic substrate is 900 kg / m 3 Higher than, for example, 1000 kg / m 3 Higher than, for example, 1100 kg / m 3 Higher than, for example, 1200 kg / m 3 The precoated cellulosic substrate may be preferably subjected to a calendaring treatment such as a supercalendering treatment in order to obtain a high density and a surface smoothness.

[0097] The lower the surface roughness, the more perfect the interface with the adjacent layers or coatings applied subsequently, with fewer defects such as pinholes and irregularities in the coating layer. As a result, the coating or further layers can be applied with higher quality and / or at a lower thickness. For the same thickness of gas barrier coating, the coating itself provides a better oxygen barrier.

[0098] The precoated cellulosic substrate, including the ductile base layer precoating, has a modulus of at least 950 kg / m2, measured according to ISO 534:2011. 3 , e.g. at least 1000 kg / m 3 , e.g. at least 1100 kg / m 3 and a density of 35 to 75 g / m 2 , for example 40 to 75 g / m 2 , for example 45-70g / m 2 , for example 45 to 65 g / m 2 The sheet may have a basis weight of

[0099] The application of a ductile base layer precoating in conjunction with calendaring of the coated cellulosic substrate improves the ductility of the precoated cellulosic substrate, which in turn improves the ductility of the final gas barrier coating material, thereby improving the gas barrier properties of the laminate packaging material and improving resistance to breakage, cracking and damage during conversion into packaging and during handling and distribution of the packages.

[0100] The increased ductility makes the paper less likely to crack and also makes the gas barrier coating less likely to crack during processes such as folding by redistributing stress and strain over a larger surface area.

[0101] The at least one gas barrier coating that provides the basic gas barrier properties to the barrier coated cellulosic substrate of the present invention can be a gas barrier dispersion coating applied by dispersion or solution coating, and / or a barrier deposition coating applied by a deposition technique.

[0102] The gas barrier coatings applied by coating of aqueous dispersions or solutions of the gas barrier compositions may be composed of polymers that have inherent gas barrier properties and are food safe and environmentally sustainable in terms of recyclability as well as in industrial coating and lamination processes. Such polymers may be water dispersible and / or soluble in water and may be applied by aqueous "dispersion coating" processes or so-called "liquid film coating" processes. Non-aqueous or only partially aqueous coating compositions, such as those based on alcohol or mixtures of alcohol and water, are also suitable for achieving good results of the present invention. However, these compositions are likely to be less suitable from the standpoint of environmental sustainability than purely aqueous coating compositions.

[0103] In one embodiment, the barrier dispersion coating comprises a polymer selected from the group consisting of vinyl alcohol polymers and copolymers, such as polyvinyl alcohol (PVOH) and ethylene vinyl alcohol (EVOH), starch, starch derivatives, xylan, xylan derivatives, nanofibril cellulose / microfibril cellulose (NFC / MFC), nanocrystalline cellulose (NCC), and blends of two or more thereof.

[0104] In a further embodiment, the barrier dispersion coating has a dry weight of 0.2 to 6 g / m 2 , for example 0.5 to 5 g / m 2 , for example 0.5 to 4 g / m 2 , for example 0.5 to 3.5 g / m 2 , for example 1 to 3.5 g / m 2 , for example 1 to 3 g / m 2 is applied by dispersion coating or solution coating in a total amount of .

[0105] These include gravure roll coating, smooth roll coating, reverse roll coating, wire bar coating, blade coating, lip coating, air knife coating, curtain flow coating methods, etc. Although the experiments of the present invention were carried out by smooth roller coating, it is believed that any of these or other liquid film coating methods that contribute to producing a homogenous layer having a smooth and uniform coating surface are suitable for providing the gas barrier coating of the present invention.

[0106] In a more specific embodiment, the barrier dispersion coating composition is based on the two most common types of polymers and copolymers suitable for dispersion coating, which are based on vinyl alcohol monomers, namely polyvinyl alcohol (PVOH) and ethylene vinyl alcohol (EVOH).

[0107] Preferably, the gas barrier polymer is PVOH because it offers good film forming properties, gas barrier properties, cost efficiency, food compatibility, and odor barrier properties.

[0108] PVOH-based gas barrier compositions exhibit optimal performance when the PVOH has a degree of saponification of at least 98%, preferably at least 99%, but even PVOH with a lower degree of saponification exhibits oxygen barrier properties.

[0109] On the other hand, since EVOH is a copolymer consisting of ethylene monomer units, it can be advantageous to provide some moisture resistance to the barrier material. The amount of ethylene monomer units varies depending on the grade of EVOH selected, but its presence sacrifices some oxygen barrier properties compared to pure PVOH. Conventional EVOH polymers are typically for extrusion and are available in weights of 3.5 g / m2. 2 It is not possible to disperse or dissolve EVOH in an aqueous medium to produce a thin liquid film coating barrier film below 5 g / m2. It is believed that in order to be water dispersible, EVOH should have a fairly large amount of vinyl alcohol monomer units and properties as close as possible to liquid film coating grades of PVOH. Thus, extrusion coated EVOH layers are inherently less similar to PVOH than EVOH grades for extrusion coating, and can be applied by extrusion coating or extrusion lamination as a single layer at 5 g / m2. 2 It is not a replacement for liquid film coated EVOH as it cannot be applied in cost effective amounts.

[0110] Nanocrystalline cellulose (NCC) is a form of nanocellulose, but is distinct from microfibril cellulose (MFC) (CMF) and nanofibril cellulose (NFC) (CNF).

[0111] The MFC / NFC may also comprise longer particles, so-called "fibrils", having a width of 3-100 nm and a length of at least 1 μm, such as up to 10 μm, for example up to 100 μm.

[0112] Both MFC and NFC have an aspect ratio of 50 or greater, while NCC / CNC may be defined as an aspect ratio of less than 50, for example according to the TAPPI draft standard WI3021.

[0113] The term "NCC" is used for shorter particles and "rod-like" particles having a width of 3-100 nm and a length of greater than 1000 nm, such as 100-3000 nm. The majority of the NCC particles in the composition should have this dimension and may be 100-500 nm long, for example 100-200 nm, and may have a small width of 3-100 nm.

[0114] The barrier dispersion coating composition may further comprise from about 1 to about 20% by weight of an inorganic layered compound, e.g., exfoliated nanoclay particles such as bentonite, based on the dry coating weight. Thus, the barrier layer may comprise from about 99 to about 80% by weight of polymer, based on the dry coating weight. Additives such as dispersion stabilizers, antifoamers, etc. may also be included in the gas barrier composition, preferably in an amount of about 1% or less by weight, based on the dry coating. The total dry content of the composition is preferably 5 to 20% by weight, e.g., 7 to 15% by weight.

[0115] Further possible additives in the barrier pre-coating composition may be polymers or compounds with functional carboxylic acid groups to improve the water vapor and oxygen barrier properties of the PVOH coating. Suitably, such polymers with functional carboxylic acid groups are selected from among ethylene acrylic acid copolymers (EAA) and ethylene methacrylic acid copolymers (EMAA) or mixtures thereof. In one embodiment, such a barrier layer mixture may essentially comprise PVOH, EAA and an inorganic laminar compound. The EAA copolymer may be included in the barrier layer in an amount of about 1-20 wt %, based on the dry coating weight.

[0116] It is believed that increasing the drying temperature leads to an esterification reaction between PVOH and EAA, and the PVOH is crosslinked by the hydrophobic EAA polymer chains and incorporated into the structure of the PVOH, further improving the oxygen and water barrier properties. Crosslinking can also be induced by the presence of polyvalent compounds, e.g. metal compounds such as metal oxides. However, such mixtures are more expensive due to the cost of additives and are not preferred from the standpoint of recyclability.

[0117] Therefore, it is more preferred to use a barrier dispersion coating that is comprised of a pure PVOH or EVOH composition, however, advantageous gas barrier results can also be obtained with barrier dispersion coatings that contain additional additives as described above.

[0118] Therefore, the barrier dispersion coating should be 0.2-5g / m 2 , for example 0.2 to 4 g / m 2 , more preferably 0.5 to 4 g / m 2 , for example 0.5 to 3.5 g / m 2 , for example 1 to 3 g / m 2 It may be applied at a total dry weight of 0.2 g / m 2 Below this, no gas barrier properties are obtained. 2 Above this level, coatings may not be cost-effective for packaging laminates due to the generally high cost of the barrier polymer and the high energy costs of evaporating the liquid. PVOH is suitable for use in packaging laminates above 0.5 g / m2. 2 Above this, a measurable level of oxygen barrier is achieved, between 0.5 and 3.5 g / m 2 Between these, a good balance of barrier properties and cost is usually achieved.

[0119] In one embodiment, the barrier dispersion coating may be applied as partial layers in two or even three successive steps with intermediate drying. When applied as two partial layers or "partial coatings", each layer is suitably applied at a thickness of 0.2 to 2.5 g / m 2 , preferably 0.5 to 1.5 g / m 2The two partial layers may be applied in an amount of 0.5 to 1.5 g / m2 each, resulting in a higher quality total layer from a smaller amount of the liquid gas barrier composition. More preferably, the two partial layers are applied in an amount of 0.5 to 1.5 g / m2 each. 2 may be applied in an amount of

[0120] Due to the unexpected improvement of the present invention, the barrier dispersion coating is not coated directly onto the paper or cellulosic substrate, but must be preceded by a first ductile base layer precoat of a polymer and material composition different from the gas barrier material composition to prepare the substrate surface for application of the gas barrier coating. The special properties of the aqueous ductile base layer precoat composition are believed to promote a dense and uniform base layer top surface for further gas barrier coatings and compatible adhesion chemistry and wetting for subsequent, for example, polyvinyl alcohol-based gas barrier coatings. However, the primary improvement is that the first ductile base layer precoat has the ability to absorb the stresses and strains of the barrier coated cellulosic substrate when folded and abused when used in laminate packaging materials.

[0121] According to another embodiment, the precoated cellulosic substrate of the base layer may alternatively or additionally comprise a vapor deposition coating of a gas barrier material selected from metals, metal oxides, inorganic oxides, and amorphous tie layer yam-like carbon coatings on the surface of its first precoated side. The vapor deposition coating may be applied by physical vapor deposition (PVD) or chemical vapor deposition (CVD), such as plasma enhanced chemical vapor deposition (PECVD). More specifically, it may be selected from the group consisting of aluminum metallized coatings and aluminum oxides (AlOx). Preferably, it is an aluminum vapor deposition coating.

[0122] In a further embodiment, the barrier coated cellulosic substrate has on its first upper surface a first coating of a gas barrier material formed by coating a dispersion or solution of an aqueous gas barrier composition followed by drying, and a vapor deposition coating of a gas barrier material, such as selected from metals, metal oxides, inorganic oxides, and an amorphous tie layer of yamond-like carbon, applied over the first barrier dispersion coating.

[0123] The barrier-coated cellulosic substrate may be coated on its upper surface with a gas barrier material by vapor deposition coating to a thickness of 2 to 80 nm, for example 2 to 50 nm, for example 2 to 45 nm.

[0124] The vapor deposition barrier coating that is ultimately applied to the top side of the cellulosic substrate is applied by physical vapor deposition (PVD) or chemical vapor deposition (CVD), such as plasma enhanced chemical vapor deposition (PECVD).

[0125] Generally, below 5 nm the barrier properties may be too low to be useful, and above 200 nm, e.g. above 100 nm, e.g. above 50 nm, depending on the type of vapor deposition coating, the barrier coating may be less flexible and therefore more likely to crack when applied to flexible substrates and more expensive.

[0126] Other examples of vapor-deposited coatings are aluminum oxide (AlOx, Al2O3) and silicon oxide (SiOx) coatings. Generally, PVD coatings of such oxides are brittle and not suitable for incorporation into packaging materials by lamination, with the exception of metallized layers, which, despite being made by PVD, have suitable mechanical properties for lamination materials.

[0127] Typically, aluminum metallization layers have a thin surface portion that essentially comprises aluminum oxide due to the nature of the metallization coating process used.

[0128] In one embodiment, such an aluminum vapor deposition layer is applied to have an optical density (OD) of 1.8 to 2.5, preferably 1.9 to 2.2. If the optical density is lower than 1.8, the barrier properties of the metallized film may be too low. On the other hand, if it exceeds 2.5, the metallized layer may become brittle and the heat resistance during the metallization process may be reduced due to the high thermal load when metallizing the substrate film for a long period of time. As a result, the quality and adhesion of the coating may be adversely affected.

[0129] Other coatings may be applied by plasma enhanced chemical vapor deposition (PECVD), which involves the deposition of vapors of compounds on a substrate in a more or less oxidizing environment. For example, silicon oxide coatings (SiOx) may be applied by PECVD processes and can provide very good barrier properties under certain coating conditions and gas recipes.

[0130] DLC defines a type of amorphous carbon material (bonded layer yamond-like carbon) that exhibits some of the typical properties of bonded layer yamond. Preferably, a hydrocarbon gas such as acetylene or methane is used as the process gas in the plasma to produce the coating of the amorphous hydrogenated carbon barrier layer, i.e. DLC, applied by PECVD vacuum process. The DLC coating applied by PECVD under vacuum provides good adhesion to adjacent polymer layers or adhesive layers in laminate packaging materials. In particular, polyolefins, especially polyethylene and polyethylene-based copolymers, provide good adhesion to adjacent polymer layers.

[0131] The at least one gas barrier coating may comprise a barrier dispersion coating first applied by dispersion coating or solution coating onto a ductile base layer pre-coating and a barrier deposition coating subsequently applied by a deposition method onto the barrier dispersion coating.

[0132] A barrier coated cellulosic substrate may further be provided that further comprises a ductile base layer coating also applied to the back side of the substrate, the further ductile coating on the other side of the cellulosic substrate ensures optimal performance during further abuse and folding of the laminate packaging material made from the barrier coated cellulosic substrate, resulting in better oxygen barrier properties for the final formed and filled packaging container.

[0133] Thus, the back side of the substrate may optionally be further coated with at least one gas barrier coating of at least one gas barrier material as defined in any of the above embodiments.

[0134] The gas barrier coated cellulosic substrate obtained by the above method provides excellent low OCTR and low WVTR even after lamination to a laminate packaging material and further folding and enclosing such laminate material in a package.

[0135] A carton-based laminate packaging material for packaging oxygen-sensitive products may comprise a bulk layer of paper or paperboard, an outermost first liquid-tight material layer, an innermost second liquid-tight material layer, and a barrier-coated cellulosic substrate of the present invention disposed inside the bulk layer of paper or paperboard, toward the inside of a packaging container made from the packaging material, between the bulk layer and the innermost second liquid-tight material layer.

[0136] The paper or paperboard bulk layer for use in the present invention will typically have a thickness of from about 100 μm to about 600 μm and a weight of from about 100 to 500 g / m 2 , preferably about 200 to 300 g / m 2 The paper may have conventional paper or paperboard of suitable packaging quality, with a surface weight of 100g.

[0137] For low-cost, long-term, aseptic packaging of liquid foods, thinner packaging laminates with thinner paper core layers may be used. Packages made from such packaging laminates resemble flexible pouch packaging that is not collapsible but pillow-like. Papers suitable for such pouch packaging typically have a surface weight of about 50 to about 140 g / m2. 2 , preferably about 70 to about 120 g / m 2 , more preferably about 70 to about 110 g / m 2 Since the barrier coating substrate in the present invention may itself contribute some stability to the laminate material, the paper layer corresponding to the "bulk" layer may be even thinner and interact with the barrier cellulosic substrate in a sandwich interaction to produce a laminate packaging material that still has the desired mechanical properties intact.

[0138] The barrier coated paper or cellulosic substrate can be bonded to the bulk layer by an intermediate adhesive, or thermoplastic polymeric bonding layer, which bonds the uncoated surface of the barrier coated paper to the bulk layer. In one embodiment, the adhesive layer can be a polyolefin layer, particularly a layer of a polyolefin copolymer or blend, such as one that contains a majority of ethylene monomer units. The bonding layer can be bonded to the barrier coated cellulosic substrate by melt extrusion laminating a molten bonding polymer as a layer between the webs and pressing the three layers simultaneously while advancing through a lamination roller nip under simultaneous cooling, thus providing a laminate structure by extrusion lamination. Melt extrusion lamination requires a sufficient amount of molten polymer (in this case typically a polyolefin such as low density polyethylene) to bond the two cold surfaces. A sufficient amount is typically 12-20 g / m 2 , in some cases 12-15g / m 2 It is.

[0139] According to an alternative embodiment, suitable adhesive or tie layers in the interior of the laminate material, for example between the bulk or core layer and the barrier-coated cellulosic substrate, or between the innermost liquid-tight, heat-sealable layer and the barrier-coated paper substrate, may be so-called adhesive thermoplastic polymers, for example modified polyolefins based mainly on LDPE or LLDPE copolymers, or graft copolymers with functional group-containing monomer units, such as carboxyl or glycidyl functional groups, for example (meth)acrylic acid monomers or maleic anhydride monomers (i.e. ethylene acrylic acid copolymers (EAA) or ethylene methacrylic acid copolymers (MAH)). For example, (meth)acrylic acid monomers or maleic anhydride (MAH) monomers (i.e. ethylene acrylic acid copolymers (EAA) or ethylene methacrylic acid copolymers (EMAA)), ethylene-glycidyl (meth)acrylate copolymers (EG(M)A) or MAH-grafted polyethylene (MAH-g-PE). Another example of such modified or adhesive polymers are so-called ionomers or ionomeric polymers. Preferably, the modified polyolefin is an ethylene acrylic acid copolymer (EAA) or an ethylene methacrylic acid copolymer (EMAA).

[0140] In another embodiment, the barrier coated cellulosic substrate can be bonded to the bulk layer by wet applying an aqueous dispersion of an adhesive composition containing an adhesive polymer binder to one surface of the webs to be laminated and pressing the two paper webs together while advancing them through a lamination roller nip, resulting in a wet lamination to provide a laminate structure. The moisture of the aqueous adhesive composition is absorbed into the fibrous cellulose network of the two paper layers and partially evaporates over time during the subsequent lamination step. Therefore, no forced drying step is required. The barrier coated cellulosic substrate can be bonded to a bulk layer with a coating thickness of 0.5-6 g / m2. 2 , for example 1 to 5 g / m 2 , for example 1 to 5 g / m 2The bulk layer may be laminated with an intercontiguous adhesive composition comprising, by dry weight, a binder selected from the group consisting of acrylic polymers and copolymers, starch, starch derivatives, cellulose derivatives, cellulose, polymers and copolymers of vinyl acetate, polymers and copolymers of vinyl alcohol, copolymers of styrene-acrylic or styrene-butadiene latex, or adhesive biolattices. Whenever possible, for environmental and sustainability considerations, adhesive binders of plant or non-fossil origin are preferred.

[0141] Such low amounts of contiguous adhesive composition can only be applied by aqueous dispersion or solution coating of the polymer binder and cannot be applied by single layer polymer melt extrusion coating or extrusion lamination due to the nature of the melt layer extrusion step. Because both surfaces of the layers to be bonded are made of cellulose, such wet lamination is accomplished by absorption of an aqueous medium into each cellulose layer, resulting in the formation of a thin, dry adhesive layer at the interface of the two layers.

[0142] Suitable materials for the outermost and innermost liquid-tight layers are thermoplastic polymers, for example polyolefins such as homopolymers or copolymers of polyethylene and polypropylene, preferably polyethylene, more preferably polyethylene selected from the group consisting of low density polyethylene (LDPE), linear LDPE (LLDPE), metallocene-catalyzed linear low density polyethylene (m-LLDPE) and blends or copolymers thereof. Such thermoplastic polymers also have the advantage that they are easily weldable, i.e. heat-sealable, with other materials of the same or similar polymer or thermoplastic behavior. According to one embodiment, the outermost heat-sealable liquid-tight layer may be LDPE, and the innermost heat-sealable liquid-tight layer may be a blend composition of m-LLDPE and LDPE to obtain optimal lamination and heat-sealing properties.

[0143] However, the outermost layer may simply provide protection against liquids and dirt, and sealing of the outer surface to another surface or object, such as an opening device, may be achieved by an additional adhesive or hot melt. For packaging of products with lower requirements regarding seal strength and airtightness, this also applies to the innermost second layer. For packaging of liquid, semi-liquid, viscous flowable products and moist foods, the quality of the packaging container depends heavily on the innermost second layer being heat sealable to produce a strong and airtight package capable of carrying the filled product under all circumstances of handling and distribution.

[0144] The same thermoplastic materials listed for the outermost and innermost layers, such as polyolefins, particularly polyethylene-based materials, may also be suitable for the adhesive layer within the laminate material, i.e., between a bulk or core layer, such as paper or paperboard, and the barrier-coated cellulosic substrate. Thus, in one embodiment, the thermoplastic adhesive layer may be a polyethylene layer, such as a low density polyethylene (LDPE) layer.

[0145] In a further embodiment, the second innermost liquid-tight heat-sealable polyolefin layer may be a pre-manufactured film of the same or similar polyolefin, as described above, in order to improve the robustness of the mechanical properties of the packaging material. Due to the manufacturing steps in film blowing and film casting operations, and the optional subsequent film orientation operation steps, the polymer of such a film acquires properties different from those possible from a merely (co)extrusion coated polyolefin layer. Thus, such pre-manufactured polymer films may contribute to the mechanical robustness of the laminate packaging material, the mechanical strength, the packaging integrity, and further reduce the loss of the barrier properties of the packaging containers formed and filled from the laminate packaging material.

[0146] The laminate packaging material may be laminated with a pre-manufactured polymer film between the barrier-coated cellulosic substrate and the second innermost liquid-tight material layer to improve the robustness of the mechanical properties of the laminate packaging material. Pre-manufactured films have a high degree of orientation of the polymer produced and therefore have different mechanical properties than a simple extrusion-coated or extrusion-laminated layer of the same or corresponding polymer. Thus, by incorporating such a film into the structure, the laminated material may have an overall increased strength and improved resistance to downstream tough processing of the material. It is preferable to avoid using such pre-manufactured films in materials, as they increase costs both from the material procurement point of view and from the lamination processing point of view. Pre-manufactured films may have different mechanical properties, ranging from a biaxially oriented tough film obtained by a simple extrusion cast film to a film produced by film blowing with inherent polymer orientation occurring in that step or with additional orientation afterwards. However, it is preferable to use a simple extrusion-coated or extrusion-laminated polymer material.

[0147] The second innermost layer of liquid-tight, heat-sealable material may be a blend of polyolefins, preferably low density polyethylene, LDPE, and metallocene-catalyzed (single-site or constrained geometry catalyzed) linear low density polyethylene, m-LLDPE. This type of polymer is currently the most used for the innermost layer, as it provides the best balance of liquid-tightness and heat-sealability, and thus the highest possible packaging quality for heat-sealed packaging containers. Careful selection of the composition of this layer allows optimization of the amount of polymer in this layer to be as low as possible.

[0148] In other embodiments, the second innermost layer of liquid-tight heat-sealable material may be or may include a prefabricated polymer film comprising a heat-sealable thermoplastic polymer material and, optionally, a further layer of material to provide improved robustness of the mechanical properties of the laminate packaging material.

[0149] The purpose of any one of the above mentioned embodiments is to add complementary properties to the laminate packaging material when the barrier-coated cellulosic substrate is simply used as the gas barrier material in the laminate structure, or when the applied coating provides only some gas barrier properties, or when the coating only has a moisture-sensitive gas barrier material. By laminating the barrier-coated cellulosic substrate to a polymer film that may provide additional moisture resistance or water vapor barrier properties, at least two different barrier materials can interact to provide an additional enhanced total barrier property to the entire laminate structure. Typical examples of such pre-fabricated films that add at least water vapor barrier properties include metallized films and polymer films that contain fillers such as flaky mineral fillers and other small particles, which help to slow the diffusion of water vapor through the laminate structure. The necessary tie layer between the barrier-coated cellulosic substrate and the additional barrier film can ensure such improved barrier properties, since the adjacent tie layer acts as a "cushion" and additional "gas or vapor transfer interface" in the laminate structure.

[0150] The outermost and innermost liquid-tight layers, and the laminate layers within the laminate structure, do not typically inherently provide a high barrier to migrating gaseous or small molecules. Their purpose is to directly barrier liquid water from penetrating the cellulosic bulk material or other paper layers. The liquid barrier layers also prevent water vapor from migrating into the cellulose to the extent that it wets, but they cannot maintain the moisture content of the laminate structure at zero or at the low level of "dry" paper (approximately 7-8% at ambient temperature, i.e., 23°C and 50% relative humidity (RH)). The moisture content of laminated carton materials for liquid-filled packaging containers is usually quite high, and migration through the material will occur unless an additional water vapor barrier is included, such as aluminum foil, vapor-deposited metallized layers, other vapor-deposited coatings, layers of inorganic materials, or other polymeric materials.

[0151] The laminate packaging material according to any of the above embodiments can provide good adhesion between adjacent layers in the laminate structure, and good quality of each and every combination of the barrier coating and the ductile base layer pre-coating, to provide good integrity when transformed into a filled package. In particular, for packaging liquids and wet foods, it is important that the interlayer adhesion within the laminate packaging material is maintained under wet packaging conditions, as is the oxygen gas barrier.

[0152] A packaging container formed from the laminated packaging material described above can be partially sealed, filled with a liquid or semi-liquid food product, and then the packaging material can be sealed to itself, optionally in combination with a plastic opening or top of the package.

[0153] In conclusion, a robust and reliable package for shelf-stable liquid food packaging is obtained by the barrier-coated cellulosic substrate and the laminate packaging material comprising it as defined by the present invention. The barrier properties are all improved, as long as they are maintained during folding of the packaging material. The laminate packaging material structure performs better for folding and forming into a formed package, both in terms of good adhesion between the barrier-coated substrate and the other layers of the laminate material, and also in terms of improved contribution to the gas barrier properties from the barrier-coated substrate itself. The latter is believed to be due to the improved flexibility and resistance to stress and deformation, thanks to the ductile base layer precoat of the barrier-coated cellulosic substrate. The ductile precoat can prevent the barrier coating and the innermost liquid-tight layer from distorting and cracking. The ductile precoat probably redistributes the high local stresses and strains in the cellulosic substrate, the barrier coating and the innermost liquid-tight layer during folding. Therefore, the strain levels are smaller and distributed over a larger area.

[0154] ( Examples and Description of the Preferred Embodiments ) Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. [Brief description of the drawings]

[0155] [Figure 1a] FIG. 1 is a cross-sectional schematic diagram illustrating an embodiment of a barrier-coated cellulosic substrate for use in accordance with the present invention. [Figure 1b] FIG. 1 is a cross-sectional schematic diagram illustrating an embodiment of a barrier-coated cellulosic substrate according to the present invention. [Figure 2a] FIG. 1b is a schematic cross-sectional view of an example of a laminate packaging material according to the present invention, comprising the barrier-coated cellulosic substrate of FIG. [Figure 2b] FIG. 1b is a schematic cross-sectional view of a laminate packaging material including the barrier-coated cellulosic substrate of FIG. [Figure 3a]1 is a schematic showing a method for dispersion coating a base layer or barrier precoat composition onto a cellulosic substrate. [Figure 3b] 1 shows a schematic diagram of a method for melt (co)extrusion coating layers of a thermoplastic heat sealable polymer and a liquid tight polymer onto a substrate to form the innermost and outermost layers of the packaging laminate of the present invention. [Figure 4a] FIG. 1 is a perspective view of a plant for physical vapor deposition (PVD) coating of substrate films using solid metal evaporation pieces. [Figure 4b] FIG. 1 is a schematic diagram of a plant for plasma enhanced chemical vapor deposition (PECVD) coating of paper substrates or films by magnetron plasma. [Figure 5a] 1 shows a typical example of a packaging container made from the laminate packaging material of the present invention. [Figure 5b] 1 shows a typical example of a packaging container made from the laminate packaging material of the present invention. [Figure 5c] 1 shows a typical example of a packaging container made from the laminate packaging material of the present invention. [Figure 5d] 1 shows a typical example of a packaging container made from the laminate packaging material of the present invention. [Figure 6] It illustrates the principle by which packaging containers are manufactured from packaging laminate in successive roll-fed, form, fill and seal steps. [Figure 7] FIG. 1 shows the effect of surface roughness on oxygen permeability of different paper substrates. [Figure 8] FIG. 1 is a cross-sectional schematic diagram of one embodiment of a cellulosic substrate precoated with a ductile base layer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0156] Working Example Example 1 To provide an optimal cellulosic substrate for the present invention, paper properties were evaluated on a laboratory scale.

[0157] Table 1 below shows the main characteristics used to select the optimal paper substrate. Several paper constructions were tested for the properties of porosity (expressed in Gurley air resistance), mechanical resistance (expressed in elongation and TEA-tensile energy absorption) and surface smoothness (expressed in Bendtsen and PPS roughness values). Paper porosity can be measured as air resistance in s / (100ml) measured by Tappi T460 om-02 or as air permeability in μm / (Pa·s) measured by ISO 5036-5:2013. For papers with very low porosity, the air permeability in μm / (Pa·s), nm / (Pa·s) or pm / (Pa·s) is determined by SCAN-P 26:78.

[0158] Of the papers tested, the structures with the lowest porosity and the highest Gurley air resistance values, values ​​that were sometimes too high to be detected by the instrument, were Paper 1, Paper 2 and Paper 11.

[0159] (Table 1) Evaluated paper substrates with different porosity, mechanical resistance and surface roughness

[0160] [Table 1]

[0161] (*) A characteristic that exceeds the detection limit of the instrument when the value is high. GPP stands for greaseproof paper, CP for precoated paper, and NC for uncoated paper.

[0162] The most suitable combination of paper properties evaluated was found to be the combination listed in Table 1 K above. To confirm that this construction was best suited for gas barrier applications, the base layer precoat and gas barrier coat formulations were applied and the oxygen transmission levels achieved for the selected paper base were verified. The ductile base layer precoat and barrier coating were applied to the felt side, or top side, of the paper.

[0163] A summary of the analyses carried out on the coated papers is given in Table 2. The surface roughness of the precoated papers was evaluated with PPS. The effect of the base layer precoat on the roughness of the paper is the change in roughness (in %) measured on the coated paper compared to the roughness measured on the uncoated paper.

[0164] Paper substrates (A, B, F, G, K) were further coated with one or two layers of nanocrystalline cellulose, NCC, and gas barrier solution (total wet thickness ~25 μm). Coating weight, roughness, kit oil resistance, grease resistance, and oxygen barrier properties were evaluated. Evaluation of these barrier coating properties showed the influence of the base paper sheet type and its initial roughness on further gas barrier coating performance.

[0165] The oil resistance was evaluated according to the Tappi T559 pm96 standard (KIT test). In this test, an organic solvent mixture is dropped onto the surface of the coated paper and then it is examined whether the organic solvent penetrates the barrier layer and is absorbed into the paper. For this evaluation, KIT test mixtures of grades 7 to 12 were used.

[0166] The oxygen barrier properties in Table 2 were evaluated using a MOCON sensor device, Ox-Tran model 2 / 22, according to ASTM D3985 and F1927-50 standards. Measurements were performed at 23°C, 70% relative humidity and 1 atm pressure, i.e. 100% oxygen. For papers with high initial surface roughness, the OTR was measured after two coating layers (because one layer does not provide a good barrier). For papers with low surface roughness, the OTR was measured with one coating layer (because it provides a good barrier).

[0167] Table 2. Summary of the analyses performed on selected coated papers for barrier applications

[0168] [Table 2]

[0169] The effect of roughness on the oxygen permeability of barrier-coated paper is shown in Figure 7.

[0170] As shown in Table 2 and as was observed, the surface roughness of the base paper has a significant impact on the final barrier performance after coating. First, the higher the surface roughness of the base paper, the higher the weight of gas barrier coating that needs to be applied. This is seen in Papers A and B, which had relatively high surface roughness and therefore required high gas barrier coating weights. Also, as observed in Papers A and B, for papers with high roughness measurements, typically above 3 μm (PPS), the NCC coating barrier solution reduced the roughness of the paper. For papers with low surface roughness, a slight increase in roughness is seen, but in μm terms, the roughness remains very low.

[0171] Secondly, as can be seen from Table 2 and Figure 7, the lower the roughness of the base paper (usually <3 μm), the better the barrier performance after barrier coating. It can be seen that with paper structures with low roughness such as G and K, excellent oxygen and grease barrier properties can be obtained with just one coating layer, whereas papers A and B, although coated with a large amount of coating, had insufficient oxygen barrier properties. This suggests that not only was the barrier performance improved, but also the number of layers required to form the barrier was reduced. When the papers were tested for grease resistance, all papers showed excellent grease barrier properties (KIT 12) Furthermore, all papers except Paper F showed grease resistance even after the paper was creased. Paper roughness has less effect on the grease barrier than on the oxygen barrier.

[0172] The performance of Paper F was different from the other papers tested. At low roughness it showed insufficient barrier performance in terms of oxygen permeability and grease resistance. From the properties of Paper K, which combines low surface roughness and low porosity with good oxygen barrier properties, it can be concluded that it is not only the roughness that influences the barrier performance, but also the composition of the paper, i.e. the porosity and the surface composition.

[0173] The surface roughness of the paper is a very important parameter that affects the effectiveness of the coating barrier layer, including the number of layers applied, the coating weight, and the barrier performance. To coat with a layer and obtain good barrier performance, the PPS roughness must be less than 3 μm. Surface roughness is not the only important parameter, the composition and resistance properties of the paper also affect the performance.

[0174] Therefore, after investigating and evaluating all the above paper substrate structures and considering the combination of the air resistance of the paper, i.e., porosity, surface roughness characteristics, and the performance of the paper in the barrier test after application on the paper, a paper structure named K was selected as the most suitable structure to continue the scale-up studies and design a proof-of-concept to verify the barrier performance.

[0175] Paper K is pre-coated and super-calendered, with a strength of 1100 kg / m 3 It has a density exceeding 100% and is made from 100% softwood kraft pulp.

[0176] Example 2 Precoated high density paper K is precoated on both sides and has a basis weight of 55 g / m 2 , all of whose contents can be repulped. Figure 8 shows the structure of precoated tissue paper K, which was determined to be the optimal combination for ensuring the performance of the gas barrier coating applied to the top surface. In the structure shown in Figure 8, the paper has a ductile coating on the top as well as the bottom surface, which will be described later. These ductile base layer coatings allow the optimal combination of low porosity and roughness to achieve the expected oxygen barrier performance. The ductile base layer precoating is applied directly on the paper fibers. The gas barrier coating is applied in a later step directly on the heaviest layer (B in Figure 8) of the top (or felt) surface of the paper.

[0177] The fiber composition designated as A in FIG. 8 is formed exclusively from cellulose pulp fibers. These fibers are made from bleached kraft softwood fibers and have a density of 30-50 g / m 2The basis weight of the coated paper is 40 to 65 g / m 2 The base paper of paper K is 35 g / m 2 Uncoated basis weight: 55g / m 2 The ductile precoating basis weight is 0.01 g / g.

[0178] In this way, the upper and lower surfaces of the fibrous composition A were coated with aqueous pre-coatings of ductile dispersion compositions. These coatings had a pH of 5.5-8, a solids content of 48-51%, a Brookfield viscosity of 100-1000 mPa·s, while the coated materials exhibited Tg in the range of -30-0 and 0-30°C and, in terms of chemical composition, could be described as an aqueous dispersion of a styrene-butadiene binder copolymer, the so-called SB-latex, and a kaolin clay filler. The pre-coating compositions used comprised about 15 wt% SB-latex, about 80 wt% kaolin filler, about 4 wt% cross-linked starch compounds, and less than 2 wt% further additives such as thickeners.

[0179] As shown in FIG. 8, the coating layer B applied to the top surface of the paper is 5-15 g / m2 applied in a single layer. 2 , for example 10 to 15 g / m 2 The coating composition exemplified in C applied to the lower / reverse side of the paper can have a weight of 1-10 g / m2 applied in a single layer. 2 and is obtained from an aqueous dispersion containing a styrene-butadiene copolymer and kaolin. Thus, coated papers such as those shown in sets A, B and C have a basis weight of 40-65 g / m 2 The resulting sheet may have a final basis weight of 100 g.

[0180] Thus, the precoated paper K having layers A, B and C as shown in FIG. 8 has a coating weight of 55 g / m 2and a final porosity lower than 100 nm / (Pa·s) as determined by ISO 5636-5:2013, which is the lower limit of the range of application of the test method, and even lower than 1 nm as determined by SCAN-P 26:78. The precoated papers had a top surface PPS roughness of 2 μm or less, i.e., about 1.8 μm. The final NCC gas barrier coated paper K in Table 2 showed a felt side surface roughness of about 2.8. Thus, the precoated and barrier coated papers of the present invention may have a PPS surface roughness lower than 3 μm, for example, between 0.5 and 3 μm.

[0181] Example 3 The mechanical resistance properties of the precoated cellulosic substrates used were investigated to demonstrate the importance and contribution of each layer of the precoated paper composition to the final application of the barrier coated substrate.

[0182] Material failure due to the nucleation and propagation of cracks in the substrate creates openings and discontinuities in the barrier coating layer, destroying the final package barrier. The greater the elongation that the substrate can undergo before failure, the more resilient it is to various loads, such as bending during packaging formation. By becoming more flexible, the structure, after precoating with a ductile material and subsequent drying and calendaring, is more able to allow the precoated paper structure to resist bending and initiation of fracture on its surface.

[0183] This behavior of reduced stiffness of the structure including cellulose fibers and top and back coatings after calendaring can be explained by the decrease in Young's modulus in both MD and CD of the paper, as shown in Tables 3 and 4. The decrease in Young's modulus means that the overall stiffness of the material structure is reduced, which allows the material to become more flexible and, as a result, more elastic and resistant to creasing and folding processes.

[0184] By pre-coating a flexible or ductile base layer onto the fibrous layer, the ductility of the final material can be improved, resulting in a material that is more resistant to breakage, cracking and damage during the packaging conversion process.

[0185] Table 3: Average values ​​obtained for the stress x strain curves of each precoated paper layer material described in Figure 7 (i.e. ABFGK) and the effect of each coating layer on the final ductility of each material in the MD direction of the paper.

[0186] [Table 3]

[0187] Table 4. Average values ​​obtained for the stress x strain curves of each precoated paper layer material in Figure 7 (i.e., ABFGK) and the effect of each coating layer on the final ductility of the material in the CD of the paper.

[0188] [Table 4]

[0189] The mechanical resistance properties of precoated and uncoated papers evaluated here, when combined with laboratory test results for barrier applications, allow understanding of the superior performance achieved. For example, the elongation at maximum load increases as the cellulosic substrate and paper are precoated (measurement "B") and further increases as the precoated paper is calendered (measurement "C"). This confirms the beneficial effect of providing a more ductile / flexible material as the substrate for gas barrier applications, as the gas barrier coated substrate can withstand higher elongations without cracking during the conversion of the packaging material into packaging.

[0190] Example 4 The invention described herein, in addition to offering unique features that make it possible to reach high oxygen barrier levels, is therefore a solution capable of replacing non-renewable components of packaging, has a high content of renewable materials and is 100% repulpable or recyclable according to the PTS RH 021 / 97 standard.

[0191] For the recycling of the thin, ductile precoated paper substrate selected for the application developed here, in addition to carrying out repulping tests according to PTS RH 021 / 97, repulping tests were carried out in the laboratory.

[0192] To evaluate repulpability in the laboratory, a paper sample of known weight was agitated for 20 minutes at 23°C using an apparatus running at 3000 revolutions per minute. It was already confirmed that the paper was repulpable after 3 minutes of agitation. No lumps were detected in the water suspension, indicating that the paper was already dispersed in the water.

[0193] Example 5 An NCC-based gas barrier coating formulation was used to coat a flexible precoated paper substrate. The formulation may contain 5-22% solids and have a viscosity of 600-2500±2 mPa·s. The chemical components of the formulation are based on NCC (CNC), PVOH and starch-based materials, contain at least 50% renewable materials (NCC and starch), e.g., at least 50% NCC, and are 100% recyclable and biodegradable.

[0194] Nanocellulose has a challenging rheology, so when added to blends with other polymers or ingredients, it alters the rheology by changing the final viscosity of the suspension. NCC (nanocrystalline cellulose or cellulose nanocrystals) is extracted from hardwood or softwood cellulosic pulp and all of its dimensions are on the nanometer scale. The NCCs used are 5-20 nm wide and 150-400 nm long, with all dimensions on the nanometer scale.

[0195] A dual layer gas barrier layer of nanocrystalline cellulose or PVOH or other gas barrier material can be formed on the top side of the ductile precoated paper, with a first gas barrier coating forming a gas barrier layer on the top side of the paper's ductile base layer precoating and a second gas barrier coating providing a second gas barrier layer on the first gas barrier coating layer.

[0196] In this case, the order of barrier layer application on the ductile precoated paper is important. The first gas barrier dispersion layer is applied by bar coating on the ductile base layer precoat on the upper side of the paper, and this layer is dried using infrared and hot air to form a homogeneous gas barrier layer on the surface. The application speed used in the test was 300-600 m / min to ensure good quality of the gas barrier coating layer formed on the ductile precoated paper surface. The first formed gas barrier dispersion layer prepares the surface to receive the second barrier dispersion layer, also formed by bar coating, on the dried first barrier dispersion layer. The applied second gas barrier dispersion layer also undergoes a deposition and drying step using infrared and hot air. It should be noted that the optimal range of drying using hot air tested for the formulation and ductile precoated paper is 90-150 °C.

[0197] Drying at the evaluated temperatures does not cause a decrease in the barrier level and ensures good film formation on the precoated paper surface even at high temperatures. Finally, to ensure proper winding and cooling of the barrier-coated paper substrate, after drying, the coated paper must be wound at a temperature below 40°C. This ensures the formation of a homogeneous film and high oxygen and grease barrier properties.

[0198] Example 6 In order to apply the gas barrier coating on a larger scale to the surface of the above-mentioned paper K, different conditions were tested. The gas barrier coating was applied on a pilot coating machine capable of using different techniques, but the application technique used to form the gas barrier coating layer applied on the ductile pre-coating B was the bar or blade coating method, with a total dry coating weight of 0.5-5 g / m2, as shown in Figure 8. 2 The coating bar was smooth and varied in diameter; here, bars of 18 to 30 mm were used. As shown in Figure 8, the gas barrier was directly coated onto a ductile precoated base paper for testing.

[0199] In the final prototype for proof of concept and upscaling, the properties of the ductile precoated paper used in the development were as shown in Table 5 below.

[0200] Table 5. Characteristics of papers used in large-scale testing

[0201] [Table 5]

[0202] In this upscaling work, it was found that precoated paper substrates with low surface roughness and low porosity generally provided good results and improved oxygen barrier levels in the formed and filled packages.

[0203] In this way, the barrier formulation containing NCC was applied onto the ductile precoat B on the top surface of the paper substrate A (Figure 8), i.e. on the top surface with the highest precoat weight, with 2 x 2.5 g / m of NCC. 2 and had a package OTR of 0.016 at 0.2 atm and 50% RH (cc / pkg / 24 hr) of 21% O2 in accordance with ASTM F1307-14.

[0204] Thus, an aqueous dispersion containing cellulose nanocrystals is applied in a first step to surface B, thereby providing a coating of about 2.5 g / m 2The final gas barrier layer of 2.5 g / m2 was solidified to prepare the surface to receive the second gas barrier dispersion coating layer. After the first layer was applied, it was dried by infrared heating and hot air convection. 2 A second layer of about 5 g / m2 was applied on the first gas barrier coating layer. 2 After the second layer is applied, it is dried using infrared heating and hot air, and finally, the solidified resin is cooled to a temperature below 40°C to prevent adhesion between sheets of paper that already have a barrier applied to their surfaces (the sheets would be glued together with the still-active, uncooled resin).

[0205] The application rate was 2.5 g / m for each partial layer to prevent excess moisture from adhering to the cellulosic substrate. 2 The use of precoated paper as described in Figure 7 allows for greater control of dimensional stability since the flexible precoat B not only acts as a surface modifier but also influences the surface roughness and porosity of the substrate.

[0206] The application technique used to form this gas barrier coating was the bar coating method. A bar with a diameter of 24 mm was used. The bar used to apply the barrier dispersion was rotated at a speed of 20 to 80 rpm in the same direction as the paper roll or at a speed of 80 to 160 rpm in the opposite direction to the paper roll.

[0207] Example 7 For comparison (Comparative Example 1), paper substrate K in Table 1 and the most suitable substrate paper for applying oxygen barrier coating, i.e., Nordic Paper's greaseproof paper "Superperga WS 32gsm Parchment FL109", were coated with 20g / m LDPE on the top surface of each. 2 It was laminated in the same manner.

[0208] The comparative paper had a surface roughness of about 36 ml / min Bendtsen on the top side, i.e. the side to be barrier coated. This paper has a more highly refined cellulose, i.e. smaller fibrous / fibrillar molecules of cellulose, with a denser surface and a tensile strength of 865 kg / m 3 This comparative paper is not 100% recyclable, and leaves behind waste of low molecular weight cellulose swollen with water.

[0209] The paper substrate K used in the present invention had a Bendtsen roughness on the top surface of about 20 ml / min.

[0210] The oxygen transmission rate through the flat laminated paper of Example 1 and Comparative Example 1 was measured using a coulometric detector and is reported in cm at a moisture level of 0.2 atmospheres of oxygen and 50% relative humidity in accordance with ASTM F1927-14. 3 / m 2 The results are shown in Table 6.

[0211] Table 6: OTR of PE-laminated flat paper at 0.2 atm and 50% RH, cm 3 / m 2 / 24 hours

[0212] [Table 6]

[0213] The results in Table 6 show that the best paper substrates previously studied as laminate samples provide better initial inherent OTR performance than the base layer precoated paper substrates of the present invention.

[0214] The precoated paper substrate from Example 7, but without the LDPE laminate layers on both sides, was instead coated with a first gas barrier coating of polyvinyl alcohol, PVOH, or NCC, respectively, on the ductile base layer precoat (top surface of the paper substrate). The PVOH used was obtained from Kuraray and had a degree of hydrolysis of at least 98%, i.e., Poval® 6-98. The PVOH dispersion was applied by smooth roller coating method in pilot scale equipment, with a wet application rate of about 15 wt.% of the aqueous dispersion of PVOH. 0.05% by volume of 1-octanol was added to the PVOH to prevent foaming. The Brookfield viscosity of the PVOH dispersion barrier composition at 23°C was 500-800 mPa·s.

[0215] The coating roller rotated at 160 rpm in the opposite direction to the web running direction. The coating was done in two stages, with the first and second layers each having a dry basis weight of 1.6 g / m2. 2 , 1.6g / m 2 It was.

[0216] The coating layer was dried using a combination of infrared radiation (IR) and hot air, the surface temperature was kept below 100°C, and the web speed during coating was approximately 300 m / min.

[0217] In another coating run on the same pilot-scale equipment, the NCC dispersion was instead applied by smooth roller coating. The coating weight of the aqueous NCC dispersion was approximately 19-20% by weight. The Brookfield viscosity of the aqueous NCC dispersion barrier composition at 23 °C was <2000 mPa·s, and at 50 °C was 1000-1200 mPa·s. Both IR and hot air were used to dry the coating layers, and the web speed during coating was approximately 300 m / min. The coating roller rotated at 80 rpm in the opposite direction to the web travel direction. Coating was done in two stages, with the first and second layers each having a dry basis weight of 1.9 g / m2. 2 , 2.7g / m 2 It was.

[0218] Then, pre-coated paper and gas barrier coated paper are applied on top of it at 20g / m 2 It was laminated with LDPE and the oxygen transmission rate was evaluated as in Example 7 and Comparative Example 1, but including a moisture level of 80%. The oxygen transmission rates are shown in (Table 7).

[0219] Table 7: OTR of pre-coated and barrier-coated papers laminated with PE

[0220] [Table 7]

[0221] From the results in Table 7, it can be seen that the OTR performance of the pre-coated and barrier coated papers is significantly improved compared to the pre-coated paper without gas barrier coating (Table 6). Both the PVOH and NCC coatings improve the OTR performance. However, both types of coatings are sensitive to humidity, with the OTR at 80% RH being higher than that at 50% RH.

[0222] Example 8 The precoated paper and gas barrier dispersion coated paper of Example 7 were metallized to an optical density of about 1.8. The metallized barrier paper was then extrusion coated laminated with paperboard and a polymer to provide a packaging material according to the following construction:

[0223] / / Outside 12g / m 2 LDPE / / Duplex CLC 80mN, 200g / m 2 , Paperboard bulk layer / LDPE 20g / m 2 Adhesive layer / barrier coated paper substrate (2x barrier coating ~4g / m 2 / Al metal OD~1.8 / adhesive layer EAA copolymer 6g / m 2 / Blend LDPE+m-LLDPE 29g / m 2 / / )

[0224] The liquid board was creased before lamination to facilitate folding of the package. Lamination of the packaging materials was carried out on a flexible pilot laminator equipped with three extrusion coating stations. The lamination speed was approximately 400 m / min.

[0225] Duplex CLC board is a conventional clay-coated board and m-LLDPE is a metallocene-catalyzed linear low density polyethylene. The barrier-coated side of the paper substrate was oriented toward the inside of the laminate structure (corresponding to the inside of the package made from the laminate material). The adhesive polymer EAA and the innermost heat-sealable layer were co-extrusion coated onto the barrier-coated paper and the outermost LDPE was extrusion coated onto the outside of the board.

[0226] The oxygen transmission rate through the flat laminate packaging material of Example 8 was measured using a coulometric detector and is reported in cm according to ASTM F1927-14. 3 / m 2 The tests were performed over a 24-hour period, with an oxygen pressure of 0.2 atmospheres and moisture levels of 50% and 80% relative humidity.

[0227] Comparative Example 2 The previously tested paper substrate, also used in Comparative Example 1, was coated with a gas barrier coating and laminated to a packaging structure in a substantially corresponding manner, except that the ductile base layer pre-coating was not included.

[0228] First, PVOH (Poval® 15-99, fully saponified PVOH) was added at 1.5 g / m 2 The resulting mixture was dispersed in two successive coats, then metallized to an optical density of about 2.3.

[0229] The barrier coated comparative paper substrate was further laminated to a packaging construction as follows.

[0230] / / Outside 12g / m 2LDPE / Duplex CLC 80mN, 200g / m 2 , Paperboard bulk layer / LDPE 20g / m 2 Adhesive layer / barrier coated paper substrate (2x barrier coating ~1.5g / m 2 / Al metal OD~2.3 / Adhesive layer EAA copolymer 6g / m 2 / Blend LDPE+m-LLDPE 19g / m 2 / / )

[0231] The OTR measurement results of the laminate packaging materials of Example 8 and Comparative Example 2 are shown in Table 8.

[0232] (Table 8) OTR of flat laminate packaging materials

[0233] [Table 8]

[0234] * Measured at 1 atm / 0.2 atm oxygen pressure ** Converted to 0.2 atmospheres of oxygen pressure

[0235] As can be seen in Table 8, the OTR values ​​of the packaging materials using precoated and barrier coated paper are higher than the packaging materials using highly refined greaseproof paper, despite the higher basis weight of the barrier coating in the precoated paper of the present invention. This is likely due to the lower OTR contribution from the paper itself in the precoated paper compared to the highly refined greaseproof paper (see Table 7).

[0236] It should also be noted that packaging materials that use pre-coated or barrier-coated papers are not as sensitive to elevated moisture levels.

[0237] Example 9 The packages were manufactured on a Tetra Pak® E3 / CompactFlex filling machine. This type of filling machine is capable of filling portion packages at a rate of 9000 packages per hour and has the flexibility to quickly change between different package formats. The packages were in Tetra Brik® format and had a volume of 200 ml.

[0238] The inside of the package is purged with nitrogen and the outside of the package is exposed to the environment surrounding the device. As oxygen permeates the package and into the nitrogen carrier gas it is carried to a coulometric sensor. The sensor reads how much oxygen has leaked into the nitrogen gas inside the package. OTR is evaluated at 0.2 atmospheres (ambient air containing 21% oxygen) per ASTM F1307-14. The unit of measurement is cm 3 / package / 24 hours.

[0239] (Table 9) Package OTR including loss factor

[0240] [Table 9]

[0241] * Use the package laminate area and corresponding OTR values ​​for flat packaging materials in Table 2.

[0242] What is interesting and surprising from Table 9 is that the OTR value of the package is improved by using precoated and barrier coated paper, even though the OTR value of the flat laminate packaging material using precoated and barrier coated paper is higher than that of the flat laminate packaging material using highly refined greaseproof paper, as can be seen from Table 7. The OTR measurement of the package is 0.013-0.016 cm instead of 0.075. 3 / package / 24 hours / 0.2 atm. Dividing the measured OTR value by the corresponding theoretical calculation value, it can also be seen that the loss factor is close to 1 when precoated and barrier-coated paper is used, compared with a loss factor of 9.6 when highly refined greaseproof paper is used. It can be seen that the gas barrier performance of flat laminate packaging materials is maintained even after folding the package when precoated and barrier-coated paper are used. This is because the precoat of the ductile base layer can reduce the effect of stress concentration in the paper. Stress concentration causes cracks to initiate and propagate through the paper. When cracks occur in the paper, the very thin barrier coating cannot withstand the high stress, resulting in cracks and a loss of gas barrier performance. Ductile materials in particular can withstand high strains and redistribute the stress concentration in the paper when folded.

[0243] Further, with reference to the accompanying drawings: One embodiment of a barrier coated cellulosic substrate 10a of the present invention is shown in cross-section in Figure 1a. The substrate 11a is a paper with a predominant proportion of cellulose fibres derived from sulfate softwood pulp, weighing 35 g / m 2 and is first provided on its upper surface with a ductile base layer pre-coating 12a by applying a latex or biopolymer binder composition, such as in this example a SB-latex binder composition in particular, by aqueous dispersion coating and then drying to evaporate the water. The dry weight of the applied ductile base layer pre-coating is about 12 g / m 2 Optionally, a further, second, ductile coating 15a of the same composition as the ductile base layer pre-coating 12a can be applied in the same manner to the opposite, uncoated side of the paper substrate 11a. The dry weight of the second ductile coating is about 5 g / m 2 The thus precoated paper substrate is then supercalendered at a surface temperature of 100-240°C by passing through a number of high pressure roller nips and at least one thermo roll.

[0244] The paper substrate is further coated with a gas barrier coating 13a made from a PVOH barrier dispersion or solution coating, Poval® 6-98 from Kuraray, on the surface of the ductile base layer pre-coating 12a. In this way, the gas barrier coating 13a is applied by aqueous dispersion coating and then dried to evaporate the water, preferably as two successive part coating steps with drying in between. The total dry weight of the PVOH barrier dispersion coating is about 3.5 g / m2. 2 Further optionally, the barrier dispersion coated paper substrate may have an aluminum barrier deposition coating 14a, i.e., an aluminum metallized layer, applied by physical vapor deposition to an OD of about 1.8 on the dry surface of the barrier dispersion coating 13a.

[0245] Figure 1b shows in cross-section a further embodiment of a barrier coated cellulosic substrate 10b of the present invention. The same paper as in Figure 1a was used as the cellulosic substrate, and a first ductile base layer pre-coating 12b of the same composition as used in Figure 1a was applied at a dry weight of about 12 g / m 2 In addition, a second ductile coating 15b of the same composition as the ductile base layer precoat 12b is similarly applied to the opposite, uncoated side of the paper substrate 11b. The dry weight of the second ductile coating is about 5 g / m 2 It is.

[0246] In this embodiment, no gas barrier dispersion coating is applied, but the first ductile base layer pre-coating 12b is directly coated with a gas barrier vapor deposition coating 14b of an aluminum vapor deposition layer with an outer diameter of about 2 mm. Meanwhile, the second ductile coating 15b is coated with a gas barrier coating 13b made from a barrier dispersion or solution coating of PVOH, Poval® 6-98 from Kuraray, as depicted in Figure 1a. The barrier coated paper substrate thus obtained has one gas barrier coating on each side of the paper and a ductile coating underneath, as a bridge layer between the paper substrate surface and the respective gas barrier coatings 14b and 13b.

[0247] In FIG. 2a, a laminate packaging material 20a of the present invention suitable for liquid carton packaging is shown, which has a bending force of 80 mN and a strength of about 200 g / m 2 The packaging laminate comprises a bulk layer 21a of paperboard having a basis weight of 100 g / m2 and an outer liquid-tight, heat-sealable layer 22a of low density polyethylene applied to the outside of the bulk layer 21a, which is directed towards the outside of the packaging container produced from the packaging laminate. This layer 22a is transparent to allow a printed decorative pattern 27a applied to the bulk layer of paper or paperboard to be seen on the outside, thereby informing the contents of the package, the packaging brand and other information targeted to consumers in retail establishments and food establishments. The polyethylene of the outer layer 22a is a conventional low density polyethylene (LDPE) of heat-sealable quality, but may also include further similar polymers including LLDPE. The application weight is about 12 g / m2. 2The innermost liquid-tight heat-sealable layer 23a is located opposite the bulk layer 21a, this layer being directed towards the inside of the packaging container produced from the packaging laminate. It will form a strong transverse heat seal of the liquid packaging container produced from the laminated packaging material. The innermost heat-sealable layer 23a thus comprises one or more combinations of polyethylenes selected from the group consisting of LDPE, linear low density polyethylene (LLDPE) and LLDPE produced by polymerizing ethylene monomers with C4-C8, more preferably C6-C8, α-olefin alkylene monomers in the presence of a metallocene catalyst, the so-called metallocene-LLDPE (m-LLDPE). This innermost layer of polyethylene has a density of about 29 g / m 2 It is.

[0248] The bulk layer 21a is laminated to the uncoated side (i.e. the side without the gas barrier coating) 25a of the barrier coated paper substrate 10a from FIG. 1a, which has an aluminum barrier deposition coating 14a, i.e. an aluminum metallized layer, applied to an outer diameter of about 1.8 by physical vapor deposition on the dry surface of the barrier dispersion coating 13a, and is laminated by an intermediate bonding layer 26a of low density polyethylene (LDPE). The intermediate bonding layer 26a is formed by melt extrusion as a thin molten curtain of polymer between the two paper webs, so that the bulk layer and the barrier coated paper substrate are laminated to each other when all three layers pass through the chilled press roller nip. The application weight of the intermediate bonding layer 26a is about 20 g / m 2 It is.

[0249] The innermost heat-sealable layer 23a may consist of one layer or alternatively may comprise two or more sub-layers of the same or different types of LDPE or LLDPE or blends thereof, and has a density of about 6 g / m 2The barrier coated paper substrate 10a is well adhered to the metallized barrier deposition coated surface 14a of the barrier coated paper substrate 10a by an intermediate coextrusion tie layer 24a of, for example, ethylene acrylic acid copolymer (EAA) in an amount of 0.1 g / m², which adheres the innermost heat sealable layer to the barrier coated paper substrate 10a by applying the layers together in a single melt coextrusion coating step of layers 24a and 23a.

[0250] In order to reduce the amount of thermoplastic polymer fraction in the recycling step, such as extrusion laminated polyethylene polymer, and to improve the resilience of the packaging material in the recycling step, the laminate layer 26a adhering the barrier coated cellulosic substrate 25a to the bulk layer 21a may instead be a thin layer of wet laminated polymer binder resulting from drying of a dispersion coated aqueous adhesive composition. Such a lamination step is carried out in an efficient cold or ambient lamination step at industrial speeds, without the energy consuming drying operations required to promote the evaporation of water. The dry weight of such an adhesive layer is, in such an embodiment, about 6 g / m 2 or preferably less, and is made from a polymer that is readily redispersible in water so that it is redispersible in the cellulosic fiber fraction in the carton fiber recycling step.

[0251] In a further embodiment, the backside of the paper substrate 11a is first coated with a second ductile coating 15a of the same or similar composition as the ductile base layer pre-coating 12a, as described in relation to FIG. 1a, at a thickness of about 5 g / m 2 The adhesive layer 26a may then be composed of an aqueous adhesive composition similar to the ductile base layer pre-coating composition 15a. In another embodiment, the paper substrate 11a may be left uncoated on the backside, while the amount of such adhesive layer 26a may be from 10 to about 12 g / m2, in order to simultaneously produce one single layer 26a that behaves as both the ductile base layer 15a and the laminating adhesive layer 26a. 2 The amount may be as high as

[0252] According to a further embodiment, not shown, the bulk layer 21a is laminated to the uncoated side (i.e., the side without the gas barrier coating) of the barrier-coated paper substrate 10a' from FIG. 1a by the same method as described above, but without the optional aluminum barrier deposition coating 14a. The inside of the barrier-coated barrier substrate is instead laminated with a prefabricated polymeric film substrate having a deposition-applied barrier deposition coating, such as a metallized coating laminated to the barrier-coated cellulosic substrate. The polymeric film substrate may be laminated to the barrier-coated cellulosic substrate by a contiguous adhesive layer of polymer, either by extrusion laminating a thermoplastic adhesive layer between two barrier-coated webs, or by wet laminating an aqueous adhesive. The metallized polymeric film substrate may include a heat-seal material layer on the opposite side of the metallized coating of the polymeric film substrate, forming a second innermost liquid-tight heat-sealable material layer. Alternatively, the metallized polymeric film substrate may be further extrusion coated with a second innermost liquid-tight heat-sealable material layer 23a. The materials and polymers are otherwise the same as the laminate packaging material of Figure 1. This is shown in Figure 2a and described above.

[0253] FIG. 2b shows another laminate packaging material 20b of the present invention for liquid carton packaging, which has a bending force of 80 mN and a strength of about 200 g / m 2 The paperboard includes a paperboard core layer 21b having a basis weight of 100 g / m² / g and further includes an outer liquid-tight, heat-sealable layer 22b of LDPE applied to the outside of bulk layer 21b as shown in Figure 2a. Additionally, a similar innermost liquid-tight, heat-sealable layer 23b is disposed on the opposite side of bulk layer 21b as described above in Figure 2a.

[0254] The bulk layer 21b is laminated to the barrier coated paper substrate described in FIG. 1b by wet lamination with an intermediate adhesive layer 26b, a thin layer of adhesive polymer, obtained by applying an aqueous dispersion of polyvinyl acetate adhesive or starch adhesive to one of the surfaces to be bonded to each other and then pressing them together in a roller nip. In this way, this lamination step is carried out in an efficient cold or ambient lamination step at industrial speeds, without energy-consuming drying operations required to promote the evaporation of water. The dry coating weight of the intermediate adhesive layer 26b is 3-5 g / m 2 This means that drying and evaporation of the adhesive layer is not required.

[0255] Therefore, the amount of thermoplastic polymer in this laminate layer can be significantly reduced compared to the conventional LDPE melt extrusion laminate adhesive layer described in Figure 2a.

[0256] The resulting laminated packaging material 20b has a barrier coated cellulosic substrate as depicted in Figure lb, with a gas barrier coating applied to each side, with a barrier deposition layer 14b (in this case a metallized layer) facing the inner and innermost layer 23b, and a barrier dispersion coating 13b facing the bulk layer 21b. Both gas barrier coatings 14b, 13b each have a ductile coating underneath them, acting as soft cushioning layers 12b, 15b, respectively.

[0257] In yet another embodiment of either the laminate structure of FIG. 2a (not shown) or the laminate structure of FIG. 2b (not shown), the innermost liquid-tight layer 23a' or 23b' may be comprised of a prefabricated blown film comprising LDPE or LLDPE polymers in any blend thereof. A barrier-coated paper substrate may be laminated to the surface of the barrier deposition coating, i.e., the aluminum metallization. A tie layer of EAA thicker than that used in FIG. 2a or 2b, or 12-20 g / m2 may be used. 2 , for example 12 to 18 g / m 2The aluminum metallization is carried out by an intermediate melt extruded laminate tie layer 24a or 24b, which may consist of a tie layer of simpler LDPE.

[0258] Alternatively, the prefabricated film 23a or 23b can be laminated at ambient (low) temperature with a separate wet lamination adhesive layer, i.e., a water-based adhesive of acrylic (co)polymer tie layer 24a' or 24b', at a thickness of 3-5 g / m 2 may be laminated to the gas barrier coating in an amount of 0.1 to 1.0% by weight of the barrier vapor deposition coating 14a. As noted above, if the barrier vapor deposition coating 14a is not applied to a barrier coated paper substrate, instead, the barrier vapor deposition coating may be applied to a prefabricated film by vapor deposition coating.

[0259] In FIG. 3a, one embodiment of the main steps of the aqueous dispersion coating 30a is shown, which can be used to apply a gas barrier coating 12 from a water gas barrier composition onto a substrate, or a ductile base layer pre-coating from a water-based latex composition. Alternatively, it can be used to apply an aqueous adhesive composition for wet laminating two webs. A web of cellulosic substrate 31a (e.g., paper 11a, 11b in FIG. 1a, 1b) is fed to a dispersion coating station 32a, where an aqueous dispersion composition is applied to the top surface of the substrate by a roller. The aqueous dispersion composition may have an aqueous content of 80-99% by weight for the barrier composition, and therefore there may be a lot of water on the wet coated substrate that needs to be dried and evaporated off by heat to form a continuous coating that is homogenous and has uniform quality in terms of barrier and surface properties, i.e., uniformity and wettability. Drying is performed by a hot air dryer 33a, which evaporates water off the substrate surface. The substrate temperature during the passage through the dryer can be kept constant below 100 °C, for example below 90 °C, for example at a temperature between 70 and 90 °C, to avoid defects in the coating. Drying can be partially assisted by radiation heat from infrared IR lamps in combination with hot air convection drying. However, in the case of pre-coating of a ductile base layer, the aqueous content is much lower and less drying is required.

[0260] The resulting web of ductile base layer precoated paper substrate 34a is optionally calendered by passing it through at least one high pressure roller nip, then advanced to cool and further wound onto a reel for intermediate storage, to be later further subjected to a gas barrier coating operation. The further coating step may be a vapor deposition coating of a barrier deposition coating 14, or a further dispersion coating operation of a gas barrier composition as described above, to provide a barrier coated cellulosic substrate.

[0261] FIG. 3b shows a process 30b for the final lamination step in the manufacture of the packaging laminate 20a or 20b of FIGS. 2a and 2b, respectively, after a bulk layer 21a, 21b has first been laminated to the barrier coated cellulosic substrate 10a or 10b of FIG. 1a or FIG. 1b (i.e., 25a or 25b of FIGS. 2a and 2b, respectively).

[0262] As described in connection with Figures 2a and 2b, the bulk layer paperboard 21a; 21b may be laminated to the barrier coated paper substrate 10a; 10b; 25a; 25b by wet cold dispersion adhesive lamination or melt extrusion lamination. The adhesive may be applied by the same or similar methods as described in connection with Figure 3a, but without the need for drying or with little or no heating.

[0263] The resulting paper prelaminate web 31b is conveyed from an intermediate storage reel or directly from a lamination station for laminating the paper prelaminate. The non-laminate side, i.e. the printed side, of the bulk layer 21a; 21b is bonded in a cooled roller nip 33 to a molten polymer curtain 32 of LDPE which forms the outermost layer 22a; 22b of the laminate material, the LDPE being extruded from an extruder feedblock and tie layer 32b. The paper prelaminate web with the outermost layer 22a; 22b coated on the printed side, i.e. on the outside, then passes through a second extruder feedblock and tie layer 34b and a lamination nip 35, where the molten polymer curtain 34 is bonded to and coated on the other side of the prelaminate, i.e. the barrier-coated side of the paper substrate 10; 25a; 25b. In this manner, the innermost heat-sealable layer 23a is coextrusion coated onto the inside of the paper prelaminate web, ultimately forming a laminate wrapper 36 which is wound up onto a storage reel (not shown).

[0264] These two co-extrusion steps in the lamination roller nips 33 and 35 may alternatively be performed as two successive steps in the reverse order.

[0265] According to another embodiment, one or both of the outermost layers can instead be applied at a pre-lamination station, where a co-extrusion coating layer is first applied to the outside of a (printed) bulk paperboard layer or onto the metallization coating of a barrier-coated paper substrate, and then the two pre-laminated paper webs are bonded together as described above.

[0266] According to a further embodiment, the innermost heat-sealable, liquid-tight thermoplastic layer is applied in the form of a prefabricated film, which is laminated to the coated side of the barrier coated paper substrate 10 .

[0267] As described in relation to Figures 2a and 2b, such innermost layers 23a'; 23b' may be laminated to the barrier coated paper substrate 10 by wet, cold dispersion adhesive lamination, or melt extrusion lamination.

[0268] Figure 4a shows a perspective view of an example of a plant 40a for the physical vapor deposition (PVD) of, for example, aluminium metal coatings onto a web substrate of the invention. The paper substrate 41 coated with the dispersion is subjected on its coated side to a continuous deposition 40 of evaporated aluminium, forming a metallised layer of aluminium, or to a mixture of oxygen and aluminium vapour, forming a vapour-deposited coating of aluminium oxide. The coating is applied with a thickness of 5-100 nm, preferably 10-50 nm, forming a barrier-coated paper 43 of the invention. The aluminium vapour is formed by ion bombardment of a solid piece of aluminium 42 onto an evaporation source. In the case of aluminium oxide coating, oxygen gas may also be injected into the plasma chamber through an inlet port.

[0269] FIG. 4b is a perspective view of an example of a plant 40b for plasma enhanced chemical vapor deposition coating (PECVD) of, for example, hydrogenated amorphous bond layer diamond-like carbon coatings on web substrates of the present invention. A web substrate 44a is subjected on one surface to continuous PECVD of plasma in a plasma reaction zone 45 formed in the space between a magnetron electrode 46 and a cooled web transport drum 47, which also functions as an electrode, and the film is advanced by the rotating drum along the circumference of the drum through the plasma reaction zone. The plasma for the deposition coating of the amorphous DLC coating layer can be generated by injecting a gas precursor composition consisting of, for example, organic hydrocarbon gases such as acetylene or methane into the plasma reaction chamber. Other gas barrier coatings may also be applied by the same main PECVD method, such as silicon oxide coatings (SiOx) starting from precursor gases of organosilicon compounds. The PECVD plasma chamber is kept under vacuum by continuously evacuating the chamber at outlet ports 48a and 48b.

[0270] FIG. 5a shows an embodiment of a packaging container 50a made from a packaging laminate according to the invention. This packaging container is particularly suitable for beverages, sauces, soups, etc. Typically, such packaging containers have a volume of about 100-1000 ml. It may be of any shape, but is preferably brick-shaped, with vertical and horizontal seals 51a and 52a, respectively, and optionally an opening device 53. In another embodiment, not shown, the packaging container may be wedge-shaped. To obtain such a "wedge shape", only the bottom of the package is folded, and the bottom horizontal heat seal is formed to be hidden under a triangular corner flap that is folded and sealed against the bottom of the package. The top horizontal seal remains unfolded. In this way, the packaging container, only partially folded, remains easy to handle and dimensionally stable enough to be placed on a shelf in a food store or on a flat surface.

[0271] Figure 5b shows an alternative packaging container 50b made from an alternative packaging laminate according to the invention, which is not dimensionally stable enough to form a parallelepiped or wedge shaped package due to the thin paper bulk layer, and no creases are formed after transverse seal 52b, and the package remains a pillow-like bag, and is sold and distributed in this form.

[0272] Figure 5c shows a gable-top package 50c that is folded and formed from a pre-cut sheet or blank of a laminate packaging material consisting of a bulk layer of paperboard and a barrier coated paper substrate of the present invention. Flat-top packages may also be formed from similar blanks.

[0273] Fig. 5d shows a bottle-like package 50d, which is a combination of a sleeve 54 formed from a pre-cut blank of the laminate packaging material of the present invention and a top 55 formed by injection molding of plastic in combination with an opening device such as a screw cork. Packages of this kind are sold, for example, under the trade names Tetra Top® and Tetra Evero®. These special packages are formed by fitting a molded top 55 with an opening device in a closed state to a cylindrical sleeve 54 of laminate packaging material, sterilizing the bottle-top capsule thus formed, filling it with food, and finally folding and sealing the bottom of the package.

[0274] Figure 6 illustrates the principle described at the beginning of this application: a web of packaging material is formed into a tube 61 by overlapping the longitudinal ends 62, 62' of the web and heat sealing them together to form an overlap joint 63. The tube is continuously filled 64 with the liquid food to be filled and divided into individual filled packages by repeating double transverse sealing 65 of the tube at predetermined intervals below the level of the filled contents in the tube. The packages 66 are separated by cutting between the double transverse seals (top and bottom seals) and finally formed into the desired geometric shape by forming folds along crease lines prepared in the material.

[0275] FIG. 7 shows the effect of surface roughness on the oxygen permeability of the coated paper shown in Table 2 under 70% RH conditions (ml / m 2 / day).

[0276] FIG. 8 shows the primary structure of a ductile cellulosic substrate A with a ductile base layer precoat B on its upper surface and, optionally, a similar ductile coating C on its back surface.

[0277] Finally, it should be noted that the present invention is not limited to the embodiments shown and described above, but may be modified within the scope of the appended claims.

Claims

1. A laminate packaging material (20a; 20b) for packaging oxygen-sensitive products, comprising a barrier-coated cellulosic substrate (10a; 10b), a first outermost protective material layer (22a; 22b), and a second innermost liquid-tight heat-sealable material layer (23a; 23b); The barrier-coated cellulosic substrate (10a; 10b) comprises: At least 900 kg / m ３ and has a density of 30 to 80 g / m ２ a cellulose-based substrate (11) having a basis weight of applying at least one gas barrier coating (13a, 14a; 14b) made of at least one gas barrier material to a first surface of the cellulosic substrate to a total thickness of 2 to 7000 nm, e.g., 2 to 5000 nm, e.g., 2 to 4000 nm; The barrier-coated cellulosic substrate (10) further comprises a ductile base layer pre-coating (12a; 12b); a ductile base layer pre-coating is applied to the surface of the first side of the cellulosic substrate (11) by dispersion coating and subsequent drying, and is disposed beneath at least one gas barrier coating (13a, 14a; 14b); The barrier-coated cellulosic substrate is suitable for imparting gas barrier properties to laminate packaging materials and their packaging. Laminated packaging material (20a; 20b).

2. the gas barrier coating (13a) is a barrier dispersion coating applied by dispersion or solution coating and / or a barrier vapor deposition coating (14a; 14b) applied by vapor deposition; The laminate packaging material of claim 1 .

3. the barrier dispersion coating (13a) comprises a polymer selected from the group consisting of vinyl alcohol polymers and copolymers, such as polyvinyl alcohol, PVOH, and ethylene vinyl alcohol, EVOH, starch and starch derivatives, xylan, xylan derivatives, nanofibril / microfibril cellulose, NFC / MFC, nanocrystalline cellulose, NCC, and blends of two or more thereof; The laminate packaging material of claim 1 .

4. the barrier vapor deposition coating (14a; 14b) is a vapor deposition coating of a material selected from metals, metal oxides, inorganic oxides and carbon coatings; The laminate packaging material of claim 1 .

5. the at least one gas barrier coating (13a, 14a) comprises a barrier dispersion coating (13a) initially applied by means of dispersion or solution coating onto the ductile base layer pre-coating, and a barrier vapor deposition coating (14a) subsequently applied by means of vapor deposition onto the barrier dispersion coating (13a); The laminate packaging material of claim 1 .

6. said ductile base layer pre-coating (12a; 12b) is made from an aqueous composition comprising a polymeric binder material with inherent ductility selected from the group consisting of styrene-butadiene copolymer (SB) latex, styrene-acrylate copolymer (SA) latex, other latexes of acrylate polymers and copolymers such as vinyl acrylate copolymer latex and vinyl acetate-acrylate copolymer latex, and bio-based polymeric materials; The laminate packaging material of claim 1 .

7. the ductile base layer pre-coating (12a; 12b) is made from an aqueous composition comprising a bio-based polymeric binder material having inherent ductility properties selected from the group consisting of starch derivatives, polyisoprene, lignin-based polymers, alginates, gums, and soy-based proteins, and a latex of one or more bio-based polymeric binder materials; The laminate packaging material of claim 1 .

8. The ductile base layer pre-coating (12a; 12b) further comprises a filler material, such as an inorganic filler. The laminate packaging material of claim 1 .

9. the ductile base layer pre-coating (12a; 12b) comprises, by dry weight, 10-20 wt % of a polymeric binder material having inherent ductile properties, 75-85 wt % of an inorganic filler, 3-5 wt % of a cross-linking compound such as starch, and 1-2 wt % of a thickener; The laminate packaging material according to claim 6.

10. The filler is an inorganic layered compound such as bentonite or kaolin, The laminate packaging material according to claim 6.

11. The ductile base layer pre-coating has a coating weight of 2 to 15 g / m ２ , for example 5 to 15 g / m ２ , for example 8 to 15 g / m ２ , for example 10 to 15 g / m ２ having a basis weight of The laminate packaging material according to claim 6.

12. the cellulosic substrate has a second ductile coating (15a; 15b) on its opposite side, the second ductile coating being of the same composition as the ductile base layer pre-coating (12a; 12b); The laminate packaging material of claim 1 .

13. % by weight, for example, 15 to 23 wt. %, as determined by ISO 1762:2019; The laminate packaging material according to claim 8.

14. The cellulosic substrate comprising the ductile base layer pre-coating (12a; 12b) has a density of at least 950 kg / m, measured according to ISO 534:2011. ３ , e.g. at least 1000 kg / m ３ , e.g. at least 1100 kg / m ３ and a basis weight of 35 to 75 g / m ２ , for example 40 to 75 g / m ２ , for example 45 to 70 g / m ２ , for example 45 to 65 g / m ２ having The laminate packaging material of claim 1 .

15. the cellulosic substrate comprising the ductile base layer pre-coating (12a; 12b) is calendered to a thickness below 100 nm / (Pa s), the lower limit of application of test method ISO 5636-5:2013, and even below 1 nm, for example between 40 and 900 nm / (Pa s); Further, the viscosity is lower than 1 nm, such as 40 to 900 pm / (Pa·s), for example 40 to 800 pm / (Pa·s), for example 100 to 700 pm / (Pa·s), for example 200 to 500 pm / (Pa·s), as determined by SCAN-P 26:78; The laminate packaging material of claim 1 .

16. the barrier coated cellulosic substrate comprising the ductile base layer pre-coating (12a; 12b) and at least one gas barrier coating (13a, 14a; 14b); wherein the gas barrier coating has a PPS surface roughness of less than 3.0 μm, such as less than 2.8 μm, for example less than 2.5 μm, such as less than 2.2 μm, for example less than 2.0 μm, such as 1.8, when measured according to TAPPI 555 om-15, which is the same as ISO 8791-4; The laminate packaging material of claim 1 .

17. % softwood cellulose, e.g., Kraft softwood cellulose; The laminate packaging material of claim 1 .

18. The pre-coated and dried cellulosic substrate having the ductile base layer pre-coating (12a; 12b) is supercalendered before being further coated with a gas barrier coating (13a, 14a; 14b). The laminate packaging material of claim 1 .

19. a bulk layer (21 a; 21 b) of paper, paperboard or other cellulose-based material; the first outermost protective material layer (22 a; 22 b); the second innermost liquid-tight heat-sealable material layer (23 a; 23 b); and the barrier-coated cellulose-based substrate (10 a; 10 b) disposed inside the bulk layer and between the bulk layer and the second innermost liquid-tight heat-sealable material layer. The laminate packaging material of claim 1 .

20. the barrier-coated cellulosic substrate (10a; 10b) is bonded to the bulk layer (21a; 21b) by an intermediate tie layer (26a; 26b) comprising a composition comprising a binder selected from the group consisting of acrylic polymers and copolymers, starch, cellulose and polysaccharide derivatives, polymers and copolymers of vinyl acetate and / or vinyl alcohol; 20. The laminate packaging material of claim 19.

21. the second, innermost liquid-tight, heat-sealable material layer (23a'; 23b') comprises a pre-fabricated polymer film for improving the robustness of the mechanical properties of the packaging material; The laminate packaging material of claim 1 .

22. the barrier-coated cellulosic substrate (10a) having a barrier dispersion coating (13a) and optionally a further barrier vapor deposition coating (14a); and further laminated to a pre-fabricated polymeric film substrate having a barrier vapor deposition coating applied by a vapor deposition method, the pre-fabricated polymeric film substrate having the barrier vapor deposition coating being disposed between the barrier-coated cellulosic substrate and the second, innermost, liquid-tight, heat-sealable material layer (23a; 23b). The laminate packaging material of claim 1 .

23. A packaging container (50a; 50b; 50c; 50d) comprising the laminate packaging material of claim 1.

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