Use of paper substrate, barrier-coated paper substrate, laminated packaging material, and packaging container containing the laminated packaging material

Abstract

The present invention relates to the use of paper substrates (10a, 10b) containing cellulose fibers as gas barrier materials in laminate packaging materials (40a) for packaging oxygen-sensitive products, and further to coating such paper substrates (30a) to enhance their gas barrier properties. The present invention also relates to laminate packaging materials (40a) made from paper substrates or barrier-coated paper substrates, and to packaging containers containing the laminate packaging materials for packaging oxygen-sensitive products such as food.

Description

[Technical Field]

[0001] The present invention relates to the use of paper substrates made from cellulose fibers as gas barrier materials in laminated packaging materials for packaging oxygen-sensitive products such as oxygen-sensitive foods, liquid, semi-liquid or viscous foods or water, and to coatings of such paper substrates to enhance their gas barrier properties when subjected to mechanical stress. The present invention further relates to laminated packaging materials comprising coated or uncoated paper substrates, and packaging containers made from the laminated packaging materials, for packaging oxygen-sensitive products. [Background technology]

[0002] Single-serve packaging containers for liquid foods are often manufactured from paperboard or carton-based packaging laminates. One such commonly used packaging container is sold under the trademark "Tetra Brik Aseptic®" and is primarily employed for the aseptic packaging of liquid foods, such as milk and fruit juice, that are sold for extended shelf life. The packaging material of this known packaging container is typically a laminate including a bulk or core layer of paper, paperboard, or other cellulose-based material and an outer liquid-tight layer of thermoplastic plastic. To render the packaging container gas-tight, and particularly oxygen-tight, for aseptic packaging of, for example, milk or fruit juice, these packaging container laminates typically include at least one additional layer, most commonly aluminum foil.

[0003] On the inside of the laminate, i.e., the side of the container made from the laminate intended to face the filled food contents, there is an innermost layer coated on the aluminum foil, which innermost layer comprises one or more sub-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 typically produced by modern high-speed packaging machines 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 overlapping joints by welding together the inner and outer heat-sealable thermoplastic polymer layers, transforming 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 predetermined distances from each other below the level of the contents within 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 scoring the packaging material along pre-prepared crease lines.

[0005] The main advantage of this continuous tube forming, filling and sealing packaging concept is that the web can be continuously sterilized just prior to 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 packages 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, as mentioned above, continuous high speed packaging is possible, which has a major impact on cost efficiency.

[0006] Packaging containers for sensitive liquid foods, such as milk or juice, can also be manufactured from sheet blanks or pre-assembled blanks of the laminate packaging material of the present invention. Packages are manufactured from flat-folded tubular blanks of the packaging laminate by first assembling the blanks to form an open tubular container capsule, and then closing one open end of the tubular container capsule by folding and heat-sealing an integral end panel. The closed container capsule is then filled with a food product, such as juice, through the other open end, and then closed by further folding and heat-sealing the corresponding integral end panel. Examples of packaging containers manufactured from sheet and tubular blanks include conventional gable-top packages. These types of packages also include those with molded plastic tops and / or screw caps.

[0007] The aluminum foil layer of packaging laminates provides significantly better gas barrier properties than other gas barrier materials. At their performance level, traditional aluminum foil-based packaging laminates for aseptic packaging of liquid foods are the most cost-effective and low-carbon footprint materials available on the market. However, efforts are underway to replace aluminum foil with non-foil barrier materials to further reduce the carbon footprint.

[0008] Other materials that compete with foil-based materials need to be cost-effective in terms of raw materials, have comparable food preservation properties, reduce the carbon footprint, and be equally less complex in converting the material into a finished packaging laminate.

[0009] In the effort to develop non-aluminum foil materials for liquid food carton packaging, there is an incentive to develop pre-fabricated films or sheets with high or multiple barrier properties that can replace aluminum foil barrier materials in conventional laminate packaging materials or combine multiple separate barrier layers in laminate materials and be compatible with conventional 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. While there are various aqueous dispersion and vapor deposition coating processes and material recipes for such coatings, there is a need for "non-foil" type, i.e., non-aluminum foil, cost-effective barrier materials with improved barrier properties, particularly against gases such as oxygen gas, for use in packaging laminates for liquid food packaging.

[0011] International Patent Publication WO 2011 / 003565 A1 discloses a non-aluminium foil packaging material comprising a dispersion coated, metallized paper or cellulose-based substrate intended for induction heat sealing.

[0012] International Patent Publication WO 2017 / 089508 A1 discloses that further improved barrier properties can be obtained in a similar manner by selecting a paper substrate that provides optimal properties from metallized papers in a similar packaging laminate. Such metallized paper substrates not only provided improved barrier properties, but also demonstrated 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 from prior art gas barrier coated paper substrates, particularly in the area of ​​liquid and wet food packaging, and there is also a growing need for improved properties related to the recyclability and environmental sustainability of materials used in gas barrier coated paper substrates and laminate packaging materials containing same. Summary of the Invention [Problem to be solved by the invention]

[0014] It is therefore an object to use an improved paper substrate that contributes to good gas barrier properties of laminated packaging materials that do not contain aluminum foil ("non-foil") and consist of a paper substrate for packaging oxygen-sensitive products.

[0015] It is also a general object to provide an improved barrier-coated paper substrate that contributes to the excellent gas barrier properties, as well as increased recyclability and environmental sustainability of such non-foil laminate packaging materials.

[0016] A further object is to provide a package made from a non-foil laminate packaging material for oxygen-sensitive products, such as aqueous liquids, semi-liquids or viscous foods, that does not contain aluminum foil and provides good barrier and gas barrier properties.

[0017] The present invention aims to provide a cost-effective, foil-free, paper- or paperboard-based laminated packaging material that has superior gas and water vapor barrier properties, as well as superior recyclability and environmental sustainability compared to aluminum foil barrier materials, for the manufacture of packages for long-term aseptic storage of liquid foods.

[0018] It is a further object of the present invention to provide a cost-effective, non-foil, paper- or paperboard-based, mechanically robust, heat-sealable packaging laminate with reliable gas and water vapor barrier properties and good interlayer adhesion for the production of aseptic packaging containers for the long-term storage of liquid foods with maintained nutritional quality under ambient conditions.

[0019] These objects can therefore be achieved according to the present invention by the use of an improved paper substrate, a barrier-coated paper substrate, a laminated packaging material comprising the improved paper substrate or the barrier-coated paper substrate, and a packaging container made from the laminated packaging material, as defined in the appended claims. [Means for solving the problem]

[0020] According to a first aspect of the present invention, there is provided the use of a paper substrate made from cellulose fibers as a gas barrier material in a laminate packaging material for packaging oxygen-sensitive products, for example for packaging oxygen-sensitive foods such as liquid, semi-liquid or viscous foods or water, wherein the paper substrate has a gas barrier capacity of 30 to 100 g / m2 measured according to ISO 536:2012. 2 and has a machine direction strain at break of greater than 3% as measured in accordance with ISO 1924-3:2005 and a Bendtsen surface roughness on at least one side of less than 150 ml / min as measured in accordance with ISO 8791-2:2013.

[0021] In one embodiment, the post-consumer paper substrate has a machine direction strain at break measured according to ISO 1924-3:2005 in the range of 3.5% to 9.0%, for example 4.0% to 8.0%.

[0022] In a further embodiment, the paper substrate has a cross-direction strain at break of greater than 5.0%, measured according to ISO 1924-3:2005.

[0023] Conventional paper has a breaking strain of about 1.5% in the machine direction (MD) and about 2.5-3% in the cross direction (CD).

[0024] The increased stretchability in the MD, i.e., strain at break, is believed to add significant flexibility properties to gas barrier coated paper structures having such paper substrates. This invention demonstrates that gas barrier coated paper substrates with a strain at break greater than 3%, when laminated to carton-based packaging materials, significantly improve the final oxygen barrier properties of the molded packaging containers formed from the laminated material.

[0025] The paper substrate may be composed of at least 90% cellulose fibers by dry weight of the paper. The paper substrate may be made from a chemical pulp, such as kraft fiber.

[0026] The paper substrate is 90 g / m2 when measured according to ISO 536:2012. 2 Below, for example, 80 g / m 2 Below, for example, 70 g / m 2 Below, for example, 66 g / m 2 Below, for example, 60 g / m 2 Below, for example, 55 g / m 2 Below, for example, 50 g / m 2 The integrity and robustness of the filled and sealed liquid carton package generally benefit from the use of thinner paper substrates to carry the barrier coating. Thinner paper reduces distortion and mechanical stress on the gas barrier coating when folded and formed into the package, and the final gas barrier properties of the filled packaging may also be improved.

[0027] In a further embodiment, the Bendtsen surface roughness of at least one surface is 100 ml / min or less, e.g., 70 ml / min or less, e.g., 50 ml / min or less. The surface smoothness of the substrate is important for the uniformity and quality of the subsequently applied gas barrier coating. A well-functioning gas barrier coating needs to be thin so that it is as flexible as possible when formed and folded into a packaging container. A thicker coating is less resistant to distortion during folding, is more difficult to apply, and is more costly. Preferably, vapor deposition or liquid dispersion gas barrier coatings are thin, so they must be of uniform and reliable quality so that the laminate packaging material that makes up the final packaging container can provide gas barrier properties at every point in the gas barrier material coating.

[0028] The paper substrate may be impregnated, at least from its top surface, with a polymer such as one selected from the group consisting of polyvinyl alcohol, PVOH, ethylene vinyl alcohol, EVOH, starch, starch derivatives, carboxymethyl cellulose, CMC, or other cellulose ethers. The top surface of the paper substrate is the side with the smoothest surface and / or the side that will be further coated with a gas barrier coating. As the paper substrate is impregnated with the polymer having a high environmentally sustainable profile, the paper undergoes pressure and filling of its porous, fibrous, internal network with the polymeric material, so that its internal bulk and surface can become more closed. The fibrous structure within the paper may be pressed together and fixed in a densified state by the dried and solidified polymer, resulting in a smooth surface.

[0029] In one embodiment, the paper substrate has a hardness of at least 800 kg / m as measured according to ISO 534:2011. 3 , at least 900 kg / m 3 , at least 1000 kg / m 3 It may have a high density such as

[0030] The paper substrate may be subjected to a calendering process such as a supercalendering process. The purpose of the calendering process is to give the paper substrate a lower surface roughness and a higher density, for example at least 800 kg / m 3 , e.g. at least 900 kg / m 3 , e.g. at least 1000 kg / m 3 The paper substrate preferably has a density of 900 kg / m 3 Higher densities, e.g. 1000 kg / m 3The paper substrates have a higher density than conventional paper substrates and provide as stable and thin a substrate and carrier as possible for the application of gas barrier coatings to withstand the various challenges encountered in the liquid carton packaging field. These challenges include, but are not limited to, packaging heavy, flowable oxygen-sensitive products, the stresses placed on various materials during conversion and manufacturing of multi-layer laminate packaging materials, the fill-form-seal operation on packaging machines, and the handling and distribution of filled and sealed packages in a variety of climates and conditions. Such high-density paper substrates provide a stable and durable support for gas barrier coatings, which are applied to liquid packaging laminates at thicknesses of only a few micrometers or even nanometers, e.g., less than 0.5 micrometers.

[0031] As an alternative to impregnation, the paper substrate may be coated with a base coating comprising a polymer applied to the top surface of the paper substrate, i.e., underneath the subsequently applied gas barrier coating. The base coating composition may comprise a polymer selected from the group consisting of polyvinyl alcohol, PVOH, ethylene vinyl alcohol, EVOH, starch, starch derivatives, carboxymethyl cellulose, CMC, or other cellulose ethers, i.e., one or more of the same polymers useful for impregnation to further improve the surface of the paper substrate.

[0032] In another embodiment, the base coating composition may comprise a polymeric binder having a Tg of -3°C or less, such as -10°C or less, such as -15°C or less, for example -20°C or less. The polymeric binder may be an acrylic or methacrylic homo- or copolymer. Other suitable polymeric binders in coating compositions for stretchable paper and paperboard applications may be polyurethane-based binders, vinyl acetate-based binders, and polyester resins with a Tg<-3°C.

[0033] The base coating composition may further comprise an inorganic filler selected from the group consisting of calcium carbonate-containing materials, talc, kaolin, clay, titanium dioxide, satin white, bentonite, and mixtures thereof. In one embodiment, the inorganic filler is selected from the group consisting of calcium carbonate-containing materials, clay, kaolin, and mixtures thereof.

[0034] The purpose of the base coating is to provide a smoother surface to the paper substrate by forming a bridge that strengthens the bond with the paper substrate with a machine direction strain to break of more than 3% and / or to improve the quality of further coatings or layers applied over the base coated surface.

[0035] The base coating may be applied by a suitable aqueous dispersion coating method, followed by drying to evaporate the water. The base coated and dried substrate may then be calendered.

[0036] The base coating may be very thin, e.g., 0.5-3 g / m 2 , for example, 0.5 to 2 g / m 2 , for example, 0.5 to 1.5 g / m 2 , for example, 0.5 to 1 g / m 2 The base coating may or may not have inherent oxygen barrier properties of the material used. A thin base coating of starch or carboxymethyl cellulose, for example, serves to provide a smooth, closed surface for a paper substrate and does not contribute significant inherent gas barrier properties.

[0037] According to a second aspect of the present invention, there is provided a gas barrier coated paper substrate for use as a gas barrier material in laminate packaging materials for oxygen sensitive products, such as oxygen sensitive foods or water, e.g. liquid, semi-liquid or viscous foods or water, wherein the paper substrate used according to the first aspect has at least one gas barrier coating of at least one gas barrier material, and the total coating thickness is from 2 to 5000 nm, for example from 2 to 4000 nm.

[0038] The at least one gas barrier coating may be formed by coating a dispersion or solution of an aqueous composition of the at least one gas barrier material, followed by drying.

[0039] In one embodiment, the upper surface of the paper substrate is coated with a gas barrier material comprising a polymer, such as a binder polymer or a coating polymer, to a dry coating thickness of 100 to 5000 nm (0.1 to 5 μm), for example 100 to 4000 nm (0.1 to 4 μm), for example 300 to 3500 nm (0.3 to 3.5 μm), for example 300 to 3000 nm (0.3 to 3 μm).

[0040] The gas barrier material may comprise a polymer selected from the group consisting of a vinyl alcohol polymer or copolymer, such as polyvinyl alcohol, PVOH, or ethylene vinyl alcohol, EVOH, and a polysaccharide or polysaccharide derivative. Suitable polysaccharides or polysaccharide derivatives may be selected from the group consisting of starch, starch derivatives, chitosan, chitosan derivatives, cellulose, cellulose derivatives, derivatives, and lignocellulosic compounds. In one embodiment, the polymer is of fully renewable (i.e., non-fossil-based) origin.

[0041] In more specific embodiments, the gas barrier material 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, NNC, and blends of two or more thereof.

[0042] In another embodiment, the upper surface of the paper substrate has a vapor-deposited coating of a gas barrier material selected from metals, metal oxides, inorganic oxides, and amorphous diamond-like carbon coatings.

[0043] Oxygen barrier properties are further improved by first impregnating the paper substrate and then coating it with a conventional coating layer. Although the conventional coating layer can be very thin, this combination can provide excellent gas barrier properties. The gas barrier performance of thin coatings (a few micrometers thick), such as those provided by dispersion or solution coating of a gas barrier composition, or those provided by nanometer-thick vapor deposition coating processes, such as PECVD, PVD, CVD, and atmospheric pressure plasma processes, is enhanced and protected by the effect of the impregnated, pore-filled paper substrate. Furthermore, the filled voids and the smoothing effect of the polymer reduce the surface roughness of the impregnated paper substrate, significantly improving the quality of the subsequently applied gas barrier coating, resulting in fewer pinholes and more uniform thickness. Therefore, the use of stretchable paper substrates in laminated packaging materials and packages for oxygen barrier purposes, when impregnated and / or base-coated and then coated with a coating of gas barrier material, provides significantly improved results due to a combination of positive effects and mechanisms.

[0044] According to a third aspect of the present invention, there is provided a laminated packaging material for packaging oxygen-sensitive products such as liquid, semi-liquid or viscous foods or oxygen-sensitive foods such as water, comprising the paper substrate of the first use embodiment or the further gas-barrier coated paper substrate of the second use embodiment, wherein the laminated packaging material further comprises a bulk layer of paper or paperboard or other cellulosic material, a first outermost liquid-tight material layer and a second innermost liquid-tight material layer.

[0045] For the purpose of carton packaging of liquid or viscous foods, the laminate packaging material may further comprise a bulk layer of paper or paperboard or other cellulosic material, a first outermost liquid-tight material layer, a second innermost liquid-tight material layer, and a paper substrate or gas-barrier coated paper substrate disposed inside the bulk layer of paper or paperboard and between the bulk layer and the second innermost layer, which second innermost layer liquid-tight material may further be a heat-sealable material layer.

[0046] According to a fourth aspect of the present invention, there is provided a packaging container for packaging oxygen-sensitive foods, such as liquid, semi-liquid or viscous foods or water, intended for packaging oxygen-sensitive foods, comprising the laminate packaging material of the third aspect. In particular, there is provided a packaging container for packaging liquid, semi-solid or viscous foods. According to one embodiment, the packaging container is at least partially manufactured from the laminate packaging material of the present invention, and according to a further embodiment, it is made entirely from the laminate packaging material.

[0047] By using a paper substrate as described above and further applying a gas barrier coating to such a paper substrate, the gas barrier properties of the laminated packaging material and the packaging container using the same can be significantly improved, and the repulpability and recyclability can also be improved, i.e., environmental sustainability can be improved.

[0048] Generally, the use of paper substrates in such laminated materials and packaging results in a high proportion of fibre that is renewable, i.e. of non-fossil origin, allowing old materials to be recycled into the production of new materials.

[0049] Additionally, paper substrates for carrying thin gas barrier material coatings of 3 or 4 micrometers or less in such materials and packaging may be pre-cut with a pre-cut aperture hole laminated, i.e., bulk layer, to improve the robustness of the hole, which is then laminated with all other layers of the laminate, including the paper substrate.

[0050] (Detailed explanation) The term "long-term shelf life" as used in connection with the present invention means that the packaging container is capable of preserving the quality of the packaged food, i.e., nutritional value, hygienic safety and taste, for at least 1 or 2 months, such as at least 3 months, preferably 6 months, such as 12 months or more, at ambient temperature conditions.

[0051] The term "package integrity" generally refers to the tightness of the package, i.e., the resistance of the package to leakage or breakage. This term encompasses the resistance of the package to the ingress of microorganisms such as bacteria, dirt, and other substances that may deteriorate the food product contained therein and shorten the expected shelf life of the package.

[0052] One major contribution to the integrity of a laminate packaging material's package comes from good internal adhesion between adjacent layers of the laminate material. Another contribution comes from the material's resistance to defects such as pinholes and ruptures within each layer of material itself. Yet another contribution comes from the strength of the seal joints where the materials are sealed together during the formation of the package. Thus, the integrity of the laminate packaging material itself is primarily focused on the adhesion between each laminate layer and its adjacent layers and its ability to withstand thermal and mechanical loads without failure during folding, sealing, etc. With regard to the sealing of the package, integrity is primarily focused on the quality of the seal joints, which is ensured by a well-functioning, robust heat-sealing operation in the filling machine and by the properly adapted heat-sealing properties of the laminate packaging material.

[0053] The term "liquid and semi-liquid foods" generally refers to foods that have a flowable content and optionally contain food particles. Non-limiting examples of contemplated foods include dairy products, milk, soy, rice, grain, seed drinks, juice, nectar, soft drinks, water, flavored water, energy drinks, sports drinks, coffee or tea drinks, coconut water, wine, soup, jalapeños, tomatoes, sauces (such as pasta sauce), legumes, olive oil, etc.

[0054] Other examples of oxygen-sensitive foods that can be packaged and protected with the laminate packaging material of the present disclosure include, for example, dry foods and / or fatty foods. Examples of fatty foods include cheese, butter, spreads, etc. Such packages may be flow-wrap packages, such as bags, or form-fill-seal (FFS) packages. They may also be packaged in jars, trays, lidded spread containers, 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, stretching), making the paper substrate-based packaging material of the present disclosure particularly suitable.

[0055] 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, an aseptic process is used when a product is aseptically filled into a packaging container. Package integrity characteristics are crucial to maintaining the sterility throughout the packaging's shelf life. For the long-term storage of the filled food, and to preserve the original taste and nutritional value, e.g., vitamin C content, it is important to have a barrier against gases and vapors, such as oxygen gas.

[0056] The term "bulk layer" usually refers to the thickest layer or the 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 structural stability of a packaging container folded from the laminate, e.g., paper, paperboard, or carton. It can also refer to the layer that provides a larger thickness distance in a sandwich structure, which further interacts with stabilizing surface layers with a higher Young's modulus on either side of the bulk layer to achieve structural stability of the formed packaging container and to achieve sufficient mechanical properties, such as bending stiffness.

[0057] Thickness measurements were performed with a transmission electron microscope using an FEI Titan 80-300. Samples may be prepared by ultramicrotomy with a Leica EM UC6 microtome.

[0058] OTR was measured on a coulometric sensor-based Oxtran 2 / 21 (Mocon) instrument according to ASTM F1927-14 and ASTM F1307-14. See the Examples for details of the OTR test method.

[0059] Thus, there is provided a use of a paper substrate for a gas barrier material in a laminate packaging material for packaging oxygen-sensitive foods such as liquid, semi-liquid or viscous foods or water, the paper substrate having a basis weight of 30 to 100 g / m2 measured in accordance with ISO 536:2012. 2 and a machine direction strain at break of greater than 3% to 9%, as measured according to ISO 1924-3:2005, and a Bendtsen surface roughness of at least one side of 5 to less than 150 ml / min, as measured according to ISO 8791-2:2013. Also provided is such a paper substrate having at least one gas barrier coating.

[0060] By refining the pulp to a high consistency, such as 20-40%, e.g., 25-38%, the stretchability, or strain at break, of the paper can be improved. This process deforms the fibers, creating kinks, or curled fibers, which enhance the extensibility of the resulting paper.

[0061] Another method is to dry the paper without shrinking or with very little shrinkage during drying. This means that the fiber network is made with fibers in a more relaxed state, without stretching. When the dried paper is subjected to a stretching force, the fiber network can deform to some extent until the fibers reach their breaking point, i.e., their strain point at break. Sack papers can be produced this way.

[0062] A third method for increasing paper stretch is to compress a wet paper web in the longitudinal direction of the fibers, i.e., the machine direction of the paper web. This type of compression builds in stretch in the machine direction. Compression of the paper web in the machine direction can be achieved using either a Clupak unit, which contains a nip section with a rubber blanket, or an Expanda unit, which contains a nip section with one steel roller and one rubber roller that rotate slower than the speed of the paper web. Both of the above methods for increasing paper stretch have the advantage that they do not require the addition of additional chemicals or stretch-promoting agents during the papermaking process.

[0063] In the context of the present invention, a double roll compactor type, usually called an Expanda unit, was used to increase the stretchability of the paper substrate. Other methods may also be used, either as single methods or combinations of method steps, depending on the desired level of stretchability and other paper properties.

[0064] The paper web may be subjected to drying in drying sections upstream and downstream of the stretching unit. The moisture content of the web in the stretching unit may be in the range of 25% to 50%, for example, 30% to 40%, for example, 30% to 38%.

[0065] To provide a paper substrate with a good oxygen barrier, the number and size of pores can be significantly reduced. Extensive refining of pulp increases the degree of fiber bonding and reduces porosity. Greaseproof paper produced by such extensive refining has a sufficiently low porosity to provide a grease barrier. Therefore, greaseproof paper has been considered in the prior art as a potential substrate or carrier for the addition of gas barrier coatings. However, the resulting pulp has high resistance to dewatering, requiring long periods of time for stock dewatering, adding cost to the manufacturing process and making it undesirable for repulping and recycling. Furthermore, further improvement in gas barrier properties is needed. Similarly, parchment paper is manufactured by immersing the fibers in sulfuric acid to gelatinize the fibers. However, this gelation reduces the dewaterability and repulpability of the fibers, and the parchment paper also acquires undesirable brittleness.

[0066] A different approach to filling the voids in fibrous cellulosic materials involves using microfibrillated cellulose (MFC) as the main component of the cellulosic material in sheets or films, which also provides some oxygen barrier properties. However, such materials are also highly resistant to dewatering, potentially creating similar problems during manufacturing and recycling processes. Therefore, for the purposes of this invention, it is undesirable to use paper substrates containing significant proportions of MFC or other types of nanocellulose in the papermaking pulp. Furthermore, MFC forms a gel in aqueous compositions rather than a solution or low-viscosity dispersion, making it unsuitable as an impregnation composition for molded and dried paper.

[0067] Thus, the paper substrate of the present disclosure can be obtained without extensive low consistency (LC) refining, which increases the speed (and reduces the energy consumption) of the papermaking process and facilitates recycling. Such relatively limited refining can be reflected by drainability measured after repulping.

[0068] The cellulose fibers of the paper substrate, after repulping according to Valmet's repulping method implemented in a Type HD400 Valmet pulper, may exhibit a Canadian Standard Freeness (CSF) value of greater than 200 ml, e.g., 200-500 ml, e.g., 200-450 ml, e.g., 200-350 ml, as measured according to ISO 5267-2:2001. Valmet's repulping method involves repulping 0.5 kg of air-dried paper, cut to 90 × 90 mm (0.09 × 0.09 m), with 15 liters of water in a Valmet pulper at 57 °C and a rotation speed of 3000 rpm for 20 minutes. The CSF values ​​of the paper substrate studied here differ significantly from those of most well-known papers in the prior art, which contain a high content of refined fibers to provide a denser, i.e., less porous, fiber structure in the paper.

[0069] In other words, as a drainage value, the paper substrate may provide a Schopper-Riegler (SR) value measured according to ISO 5267-1:1999 of 30 to 50, e.g., 33 to 50, e.g., 35 to 50, after repulping according to the standard method of ISO 5263-1:2004. The SR values ​​of the studied papers are significantly lower than the SR values ​​of paper substrates used in the prior art.

[0070] Both the CSF and SR values ​​measure the dewatering properties of the fibers in cellulose fiber pulp and indicate how easy or difficult it is to repulp and recycle the fibers from the paper substrate, thereby recycling laminated packaging materials that comprise the paper substrate.

[0071] Following the same logic, a stretchable paper substrate formed from cellulose fibers may have an average fines content, as measured by an L&W Fibretester+ (ABB, Lorentzen & Wettre, Sweden), of less than 40%, e.g., less than 35%, e.g., less than 32%, as measured according to ISO 16065-2:2014 after repulping according to ISO 5263-1:2004. Here, fines are defined as fibrous particles shorter than 0.2 mm. For example, the fines content of greaseproof paper after repulping is typically higher, e.g., 40% or more, e.g., at least 35% or more, due to the manufacturing process for such paper using pulp with a high content of refined fibers. A typical lower limit for the average fines content is 15% or 20%.

[0072] The paper substrate for use in the present invention may be formed from cellulosic fibers comprising at least 50% by dry weight of sulfate pulp, i.e. chemical pulp such as kraft pulp or sulfite pulp, for example at least 75% by dry weight of chemical pulp, for example at least 85% by dry weight of chemical pulp, for example at least 90% by dry weight of chemical pulp, for example at least 95% by dry weight of chemical pulp. Sulfate or sulfite pulp is used to obtain a paper that is strong enough for downstream processes such as coating (which may be carried out at high speeds) and for converting and forming into final packaging.

[0073] Sulfate / kraft pulps are preferred because they are widely produced in large quantities. However, sulfite pulps are also useful because they are generally easier to refine than sulfate pulps. Sulfite pulps have a high degree of fiber swelling, which is a disadvantage from a drying perspective (higher energy demands during drying) but an advantage from a density perspective (swelling improves fiber compliance, resulting in denser sheets). Kraft pulps are advantageous for improved repulping during recycling and general fiber dewatering. Sulfite fibers typically have a high percentage of refined fiber, which may have some adverse effects depending on the amount and degree of refining. Therefore, kraft pulp is preferred according to one embodiment of the present invention.

[0074] The paper substrate may be formed from cellulose fibers comprising 35-100%, for example 35-80%, for example 40-70% softwood pulp, 0-65%, for example 20-65%, for example 30-60% hardwood pulp, and optionally 0-15%, for example 0-10% CTMP pulp, based on the dry weight of the pulp used to form the paper. Thus, the paper substrate may be formed from cellulose fibers comprising 35-80%, for example 40-70% softwood pulp, 20-65%, for example 30-60% hardwood pulp, and optionally 0-15%, for example 0-10% CTMP pulp, based on the dry weight of the pulp used to form the paper.

[0075] The advantage of including hardwood pulp is that it disintegrates relatively easily during refining, while allowing for efficient dewatering in the wire section of the paper machine. The advantage of including softwood pulp is that it improves runnability on the paper machine and improves the strength / toughness properties of the resulting paper. The latter property can be improved by subjecting softwood pulp to high consistency (HC) refining. HC refining can also increase the breaking strain value. HC refining refers to refining to a high consistency of 20% to 40%, preferably 25% to 38%.

[0076] Pulp of this composition is advantageous for general dewatering characteristics in the repulping and papermaking processes during recycling, as well as for high-quality recycled fibers. It is also advantageous when the proportion of softwood pulp is relatively high, e.g., at least 60%, e.g., at least 70%, and when the pulp used in paper production has a Schopper-Riegler (SR) value, measured according to ISO 5267-1:1999, of 25 to 35. Such an SR value facilitates a sufficiently high density of the paper substrate without causing problems in dewatering and / or recycling, and may be obtained by adjusting the degree of low consistency (LC) refining.

[0077] At SR values ​​above 35, it becomes difficult to dewater the diluted pulp quickly enough in the forming section. At SR values ​​below 25, the final product generally has poor properties. At a consistency of diluted pulp above 0.9%, there is a risk that the paper will become too porous and the surface of the paper will become too rough when producing paper substrate for use in the present application.

[0078] When the proportion of hardwood pulp in the furnish is relatively high, e.g., at least 65% by dry weight pulp, e.g., at least 75% by dry weight pulp, the Schopper-Riegler (°SR) value measured according to ISO 5267-1:1999 may be 33 to 50, e.g., 40 to 50. Such SR values ​​may be obtained by adjusting the degree of low consistency (LC) refining to promote sufficiently high density without causing problems in dewatering and / or recycling.

[0079] The pulp may be diluted to a consistency of 0.1% to 0.5%, for example 0.1% to 0.4%, to reduce fiber clumping which reduces the porosity of the final paper.

[0080] Preferably, the softwood fibers used in the paper substrate are high consistency (HC) scoured so that the fibers acquire some inherent stretch in the paper substrate.

[0081] When softwood pulp is used, high consistency (HC) refining can be performed, i.e., the weight concentration of dry fiber in the pulp is 20% to 40%, for example, 25% to 38%. The specific energy of the HC refining step can be at least 100 kWh / ton, for example, at least 150 kWh / ton, for example, 150 to 300 kWh / ton. The unit "ton" refers to tons of dry fiber.

[0082] The pulp may be bleached, which may reduce the concentration of elements or compounds that cause contamination and / or odor in the final package.

[0083] Thus, paper can be formed by providing a pulp containing at least 50% by dry weight of a chemical pulp, such as kraft pulp or sulfite pulp, having a Schopper-Riegler value of 25-50, e.g., 25-45, e.g., 25-35; diluting the pulp to a low consistency of 0.1-0.9%; forming a paper web from the diluted pulp in a forming section; and dewatering the formed paper web in a press section to obtain an intermediate dry matter content. To further improve water repellency and dewatering, the pulp may contain less than 10% by dry weight, e.g., less than 5%, of a pigment or inorganic filler, e.g., less than 3% by dry weight, e.g., less than 1%, e.g., substantially no pigment or inorganic filler. Silica or bentonite, used as a retention agent, is typically present in an amount of less than 1 kg per ton of dry pulp and is not considered an inorganic filler. Therefore, the ash content of the pulp according to ISO 2144:2015 is preferably less than 5%, e.g., less than 3%, e.g., less than 1%. After wet pressing, the web may be dried to about 65% fiber weight for compression in the machine direction before entering the stretching unit.

[0084] According to specific embodiments, a paper substrate having a top layer and a bottom layer, i.e., a two-ply configuration, may be used. Such a paper substrate allows its properties to be better tailored to the needs. In such a configuration, the properties of the top layer may be tailored to accommodate another barrier layer, and the properties of the bottom layer may be tailored for strength / toughness. Hardwood pulp may improve the surface of the other barrier layer. Softwood pulp may improve runnability on the paper machine and provide beneficial strength / toughness properties to the resulting paper product.

[0085] For example, the top layer may be formed from at least 50% by dry weight hardwood pulp, such as at least 65% by dry weight hardwood pulp, for example at least 75% by dry weight hardwood pulp, to allow for a denser and smoother top surface of the impregnated and calendered paper.

[0086] Alternatively, the bottom layer may be formed from at least 50% by weight dry softwood pulp, such as at least 65% by weight dry softwood pulp, for example at least 75% by weight dry softwood pulp. This may allow for easier dewatering and repulping properties, or may simply make the paper cheaper to manufacture. If it is desired to impregnate such a backside surface, a larger amount of impregnation composition or impregnation polymer may be required.

[0087] The two-ply paper may include the method steps of using a first wire to form a first web that will be the top layer, and using a second wire to form a second web that will be the second layer, and joining the first and second webs.

[0088] The first web may be formed from a first formulation including at least 50% by weight dry hardwood pulp, such as at least 65% by weight dry hardwood pulp, for example at least 75% by weight dry hardwood pulp. The headbox consistency of the first formulation may be between 0.12% and 0.60%, for example between 0.18% and 0.35%.

[0089] The Schopper-Riegler (°SR) value, measured according to ISO 5267-1:1999, of the first formulation in the headbox may be between 33 and 50, for example between 40 and 50. Such SR values ​​may be obtained by adjusting the degree of low-concentration (LC) refining to facilitate a sufficiently high density without causing dewatering and / or recycling problems.

[0090] The second web can be formed from a second formulation comprising at least 50% by weight dry softwood pulp, e.g., at least 65% by weight dry softwood pulp, e.g., at least 75% by weight dry softwood pulp. The softwood pulp preferably has been subjected to high consistency (HC) refining (suitable specific energies are discussed above). The headbox consistency of the second formulation can be 0.06% to 0.40%, e.g., 0.10% to 0.25%.

[0091] In one embodiment, the headbox consistency of the second formulation is lower than the headbox consistency of the first formulation.

[0092] The Schopper-Riegler (°SR) value, measured according to ISO 5267-1:1999, of the second formulation in the headbox may be between 25 and 35. Such SR values ​​may be obtained by adjusting the degree of low consistency (LC) refining to promote a sufficiently high density without causing dewatering and / or recycling problems.

[0093] Preferably it contains less than 2% by weight of inorganic filler, for example less than 1% by weight by dry weight of inorganic filler, for example it is substantially free of inorganic filler.

[0094] In the production of two-ply papers, an intermediate coating or the addition of starch or PVOH may optionally be added before the top and bottom layers are laminated together.

[0095] The density of the paper substrate may preferably be 1050 to 1500 Kg / m3, for example 1100 to 1400 Kg / m3, for example 1100 to 1300 Kg / m3.

[0096] An impregnation composition comprising a polymer in aqueous solution can be useful to fix the fibrous network in a locked position when subsequently calendered and dried. Paper densification can contribute to the success of the present invention by providing direct and indirect gas barrier properties through the use of such paper substrates.

[0097] The paper substrate may have a tensile strength index in the MD of at least 90 Nm / g, such as at least 100 Nm / g, for example from 90 to 150 Nm / g, and in the CD of at least 40 Nm / g, such as at least 50 Nm / g, for example from 55 to 90 Nm / g, for example from 60 to 90 Nm / g. The tensile strength index is measured according to ISO 1924-3:2005.

[0098] A higher tensile strength index indicates a paper substrate, which can be useful in withstanding web handling forces during coating and lamination operations.

[0099] Preferably, beneficial barrier properties and recyclability are achieved without sacrificing strength, such as tensile strength or tear strength. After the stretching unit and compression operations, the paper web may be impregnated with an aqueous composition containing a water-soluble or water-dispersible polymer, such as in a size press or film press operation, and dried in a post-drying section to form a paper substrate having a moisture content of 4-7%. Reducing the moisture content before impregnation allows the pores of the web to be filled.

[0100] The impregnating step may comprise adding an aqueous composition comprising an impregnating polymer to at least the top surface of the paper substrate, or to each surface of the paper substrate. The top surface of the paper substrate is the surface that will be further coated with the gas barrier coating and is typically the smoothest surface of the paper substrate.

[0101] The viscosity of the aqueous composition measured at 60°C may be 55 to 90 mPa·s. Such a relatively low viscosity facilitates penetration of the polymer into the fibrous web. The concentration of the impregnating polymer in the aqueous composition is preferably 7.0% to 13.0% (w / v), for example, 8.0% to 12.0% (w / v). The 60°C viscosity measurement is preferably performed using a Brookfield rotational viscometer equipped with spindle No. 3 at 100 rpm.

[0102] To promote further densification, the impregnated paper may then be moistened to a moisture content of 10-30%, e.g., 11-20%, before being subjected to calendering in a calendering device including at least two heated nips. Calendering may be carried out in at least one supercalender, preferably having 8-20 rolls, e.g., 9-19 rolls, e.g., 11-17 rolls, and some moisture, e.g., 11-20% moisture, may be applied to the paper web again immediately before calendering. The total nip impulse of the supercalendering may be at least 600 kPa·s. The surface temperature of the heated calender rolls may be 120-160°C.

[0103] The moisture content of the paper web facilitates calendering, increases the density of the final paper, reduces porosity and provides improved surface properties.

[0104] During the calendering process, the paper is dried. Extra drying can be achieved by carrying out additional drying immediately after calendering (i.e. before reeling). An air dryer can be used for this additional drying. This setup allows the moisture content to be below 4%, which can be advantageous for subsequent coating operations, such as vapor deposition coating operations.

[0105] In one embodiment, a paper substrate suitable for use in the present invention is prepared by impregnating the thus formed paper with an aqueous impregnation composition comprising a water-soluble or water-dispersible polymer at a concentration of 5 to 20% by weight, such as 5 to 15% by weight, for example 7 to 13% by weight, for example 8 to 12% by weight, by a size press or film press operation, and then pressing the thus impregnated paper under pressure at 800 kg / m 3 , e.g., 900 kg / m 3 , e.g., 1000 kg / m 3 The high density may be obtained by calendering and drying to a density of greater than 1050 kg / m. The high density may preferably be obtained by supercalendering. In one embodiment, the density is at least 1050 kg / m. 3 , e.g., at least 1070 kg / m3 A typical upper limit for density is 1400 kg / m 3 , e.g., 1300 kg / m 3 It could be.

[0106] By impregnating paper with an aqueous impregnation composition containing one or more of the above polymers, the internal porous network of cellulose fibers beneath the paper's surface is filled and surrounded by the polymer. When the paper is calendered, the polymer (being slightly more elastic than cellulose fibers) holds the paper's fibrous mass more tightly, reducing void spaces between them and keeping it in a fixed position. This prevents interfiber channels from opening up through the material, even when the material is subjected to mechanical abuse such as folding or twisting. This is primarily due to the pore-filling effect of the polymer, which should have an affinity for cellulose, and the polymer's ability to hold the fibers together, directly affecting gas and oxygen molecules attempting to diffuse through porous materials. It may also have an indirect effect of improving the gas barrier properties of the paper substrate. That is, the pore-filling polymer evens out the irregularities of the paper's fibrous surface, creating a non-porous, well-defined interface for further application of aqueous dispersion barrier coatings or polymer extrusion coatings. This eliminates air entrapment at the interface, which can lead to coating defects and compromise the airtightness of laminates.

[0107] In one embodiment, a suitable impregnation composition may comprise a majority, i.e., at least 50% by weight, of an impregnation polymer selected from PVOH, EVOH starch, and starch derivatives, as these materials are relatively easy to handle, readily prepared as low-viscosity solutions suitable for impregnation, and relatively cost-effective. Impregnation compositions comprising a majority, i.e., at least 50% by weight, of an impregnation polymer selected from PVOH and EVOH are preferred, as they typically provide better oxygen barrier properties within this group.

[0108] The degree of hydrolysis of the PVOH can be 96% to 100%, for example, 97% to 100%, for example, 97% to 99%. PVOH with a high degree of hydrolysis is less sensitive to water and is preferred both during production and use. The weight average molecular weight (Mw) of the PVOH can preferably be less than 100,000 g / mol, for example, 10,000 to 90,000 g / mol, for example, 30,000 to 80,000 g / mol. Such relatively low Mw PVOH has a relatively low viscosity at a relatively high concentration, making it preferred during impregnation. PVOH with a low Mw has a greater tendency to penetrate into the fibrous web or paper substrate rather than remaining on the surface of the paper.

[0109] The viscosity of the PVOH, measured according to DIN 53015, is preferably less than 20 mPa·s, for example from 5 to 16 mPa·s, for example from 6 to 13 mPa·s.

[0110] The degree of polymerization (DP) of PVOH is preferably less than 3000, for example, 1000 to 2000. The DP can be determined from the viscosity-average degree of polymerization obtained from the viscosity in water. In this case, the viscosity is measured in a 4% aqueous solution at 20°C using a Brookfield synchronous motor rotational viscometer.

[0111] An example of a suitable PVOH is Kuraray Boval® 10 / 98, which has a viscosity of 10 mPa·s, a degree of hydrolysis of 98%, a DP of about 1400, and a Mw of about 61,000 g / mol. Another suitable example is Kuraray Boval® 6 / 98, which has a viscosity of 6 mPa·s and a degree of hydrolysis of 98%.

[0112] Depending on the application, it may be beneficial to choose EVOH as the impregnating polymer. EVOH has high moisture resistance and excellent oxygen barrier properties. An example of a suitable low-viscosity formulation of EVOH is Kuraray's Exeval® AQ-4104.

[0113] The impregnation composition may contain substantial amounts of nanocrystalline cellulose, "NCC" (or "CNC"), or a mixture of NCC with starch or PVOH, adjusted to a viscosity suitable for impregnation. NCC is attractive as a future barrier material in packaging because it is a cellulose and may offer good oxygen barrier properties, but may not currently be a cost-effective alternative for large-scale use.

[0114] Nanocrystalline cellulose (NCC) is a form of nanocellulose, but is distinct from "microfibril cellulose (MFC)" (CMF) and "nanofibril cellulose (NFC)" (CNF). The term "MFC" is commonly and sometimes incorrectly applied to any type of fibrillated cellulose, but a more scientific view is that "MFC" should refer to nanoscale cellulose fibrils or fibril aggregates with at least one dimension less than 100 nm.

[0115] Therefore, the MFC may include long particles, so-called "fibrils," having a width of 10 to 100 nm and a length of at least 1 μm, for example up to 10 μm, such as 10 μm or more.

[0116] Both MFC and NFC have aspect ratios of 50 or greater, while NCC may be defined as having an aspect ratio of 50 or less, for example, according to the TAPPI standard WI3021 draft.

[0117] The term "NCC" is used for shorter particles and "rod-like" particles having a width of 3-50 nm and a length of 100-1000 nm, e.g., 100-900 nm, e.g., 100-500 nm, e.g., 100-200 nm. The preferred size of NCC for the purpose of impregnating and filling the pores of formed paper means that the majority of the NCC particles in the composition should have this size, and may have a length of 100-500 nm, e.g., 100-200 nm, and a small width of 3-50 nm.

[0118] The amount of impregnated polymer is 0.5 to 4 g / m2 in dry weight. 2, e.g., 1 to 3 g / m 2 The upper surface may have at least 1 or 2 g / m 2 The impregnation composition may consist essentially of water and the impregnation polymer.

[0119] Depending on the type of cellulose fiber selected for the backside, the backside may also be impregnated. The polymer may be impregnated throughout the cellulose voids throughout the entire thickness of the paper, or it may be partially impregnated in the center / intermediate portion of the thickness of the paper. It is considered desirable to impregnate as much polymer as possible to optimize the gas barrier properties of the paper substrate. However, the amount of impregnated polymer must be balanced with the repulpability characteristics of the paper to ensure that the paper is useful in the post-consumer recycling process. It may also be preferable to impregnate both sides of the paper to avoid curling of the dried paper substrate, which can cause problems in subsequent coating and lamination processes.

[0120] Thus, "impregnation" means that the impregnation composition and impregnation polymer have penetrated the fibrous web to a substantial extent, i.e., have penetrated the cellulose fibers of the paper substrate to a substantial extent. However, it does not necessarily mean that the fibrous web is completely saturated with polymer throughout its thickness. As a result, the paper substrate may contain unfilled pores, especially in the center. Therefore, the paper substrate and fibrous web are impregnated to a substantial extent with a polymer content of 0.3 to 4.0 g / m. 2 , for example, 0.5 to 3.0 g / m 2 The substrate may be impregnated with an impregnation composition comprising an amount of an impregnation polymer.

[0121] To facilitate application and impregnation of the polymer, it is water-soluble or water-dispersible.

[0122] The extent and depth of polymer impregnation through the thickness of the paper substrate may be examined using an SEM microscope by taking cross-sectional slices of the paper, which may be done using, for example, a cryomicrotome.

[0123] The type of polymer used in the impregnation composition may be determined by FTIR spectroscopy or a combination of FTIR and other spectroscopic methods.

[0124] According to one embodiment, a paper substrate is used, which is impregnated and then calendered, so that the surface roughness of the top side, measured according to SS-ISO 8791-2:2013, can be less than 100 ml / min benzene, such as less than 80 ml / min benzene, for example 7-80 ml / min Bentothen, such as 7-50 ml / min Bentothen, for example 7-30 ml / min Bentothen, for example 7-25 ml / min Bentothen, for example 7-20 ml / min Bentothen, etc. A typical lower limit can be 5 or 7 ml / min Bentothen.

[0125] Another method of measuring surface roughness is the Parker Printed Surface (PPS) roughness, which, when measured according to SS-ISO 8791-4:2013, should exhibit a value of 1.0 to 2.0 μm, for example 1.2 to 1.8 μm.

[0126] Furthermore, the Gurley value of the paper substrate according to ISO 5636-5:2013 may be greater than 220 seconds, which means that the surface of the high-density paper substrate is closed, i.e., it does not trap air or oxygen between the surface fibers.

[0127] Lower surface roughness reduces defects such as pinholes and unevenness in the coating layer, resulting in a perfect interface with adjacent layers or coatings applied subsequently. As a result, coatings or additional layers can be produced with higher quality and / or thinner thicknesses. For the same thickness of gas barrier coating, the coating itself provides better oxygen barrier properties.

[0128] The impregnation step is preferably carried out using a size press or film press. A film press is the most preferred device. If the film press is a double-sided type, the backside of the paper web can also be impregnated to further reduce the porosity of the final paper substrate and / or to control curl. The film press may use an OptiSizer Film (Valmet) or a SpeedSizer (Voith). After film pressing, the web is dried to a moisture content of 12% to 25%, preferably about 15%. This drying is preferably carried out by non-contact drying using hot air until the primer no longer adheres to the hot metal surface, followed by drying with a steam-heated cylinder. Impregnating only one side of the paper with the impregnation composition can cause the paper to curl. Therefore, impregnating both sides of the paper results in a flatter and more balanced paper substrate.

[0129] Thus, the paper substrate may further be impregnated on the opposite, back surface of the paper with an impregnation composition comprising an impregnation polymer selected from the same group as for the top surface of the paper. The paper may be impregnated from the back and then calendered so that the roughness of the back surface is less than 200 ml / min Bendtsen, for example less than 150 ml / min Bendtsen, as measured according to SS-ISO 8791-2:2013.

[0130] Therefore, the amount of impregnated polymer on the top surface of the paper substrate is 0.3-4 g / m2 on a dry weight basis. 2 , for example, 0.3 to 3 g / m 2 , e.g., 0.3 to 2 g / m 2 , e.g., 0.5 to 3 g / m 2 , for example, 0.5 to 2 g / m 2 It could be.

[0131] The impregnation composition may comprise a water-soluble or water-dispersible impregnation polymer selected from polyvinyl alcohol (PVOH) and ethylene vinyl alcohol (EVOH), optionally further comprising a crosslinker such as glyoxal in a weight ratio of 100:3 to 100:12, e.g., 100:3 to 100:9. Preferably, the impregnation composition is an aqueous solution of a polymer having a low molecular weight and therefore a low viscosity. Suitable formulations for PVOH include low-viscosity grades of Kuraray's Poval®. An example of a low-viscosity formulation of EVOH is Kuraray's Exeval® AQ-4104. The degree of hydrolysis of the PVOH is preferably as high as possible, such as 98% or 99%, and similarly, low-molecular-weight PVOH may be preferred for optimal impregnation effectiveness. In a further embodiment, the impregnation polymer may be starch or a starch derivative, such as carboxymethylcellulose, in an aqueous solution. Anionic starch aqueous solutions are preferred due to their good affinity with cellulose.

[0132] In one embodiment, the impregnating polymer for the back surface of the paper may also be selected from polyvinyl alcohol, PVOH, and ethylene vinyl alcohol, EVOH, in aqueous solution, optionally further comprising a crosslinker such as glyoxal, for example, in a weight ratio of PVOH to glyoxal of 100:3 to 100:12, for example, 100:3 to 100:9.

[0133] In another embodiment, the polymer impregnated on the back surface of the paper may instead be starch or starch derivatives, carboxymethyl cellulose, etc. in aqueous solution. This has the advantage that the paper substrate does not stick from back to top when wound onto a reel for transport or storage. Furthermore, it can prevent curling of the paper web during manufacturing.

[0134] In addition to the impregnating polymer, the impregnating composition may further comprise a small amount of inorganic particles selected from the group consisting of clays such as bentonite, kaolin, or barite, and talcum, CaCO3, or silica particles. The particle size is preferably as small as possible for better impregnation properties, but together with the impregnating binder polymer of the impregnating composition, it may support the filling of voids between the cellulose fibers.

[0135] The impregnation composition may penetrate through most of the thickness of the paper substrate web. Impregnation may occur from both the top and backside of the paper, partially or completely through to the center of the paper.

[0136] The basis weight of the impregnated paper substrate is, in one embodiment, 35 to 60 g / m 2 , for example, 35 to 55 g / m 2 , for example 35 to 50 g / m 2 , for example 30-70, for example 30-80, for example 30-66, for example 30-90.

[0137] The thickness of the impregnated paper substrate may be 30-95 μm, such as 30-85 μm, for example 30-75 μm, for example 30-70 μm, for example 35-65 μm, for example 35-60 μm, for example 35-55 μm.

[0138] In applications such as liquid-tight packaging of wet, liquid, or viscous products, it has been found advantageous to use as thin a paper substrate as possible, as this reduces the amount of polymer required for the adjacent liquid-tight or heat-sealable layers. Such thermoplastic layers are typically melt-extrusion laminated to the paper substrate, for example, polyolefin or other thermoplastic layers.

[0139] As an alternative to impregnation, the paper substrate may also be coated with a preliminary base coating on its upper surface. Thus, the paper substrate may have a thin, continuous layer of a base coating containing a polymer applied to the upper surface of the paper substrate and positioned underneath the subsequently applied gas barrier coating, and the surface. To further improve the surface of the paper substrate, the base coating composition may include a polymer selected from the group consisting of polyvinyl alcohol, PVOH, ethylene vinyl alcohol, EVOH, starch, starch derivatives, carboxymethyl cellulose, CMC, or other cellulose ethers, i.e., one or more of the same polymers useful for impregnation.

[0140] Single-sided basecoating of the paper with a wet basecoating composition on only one side can cause the paper to curl. Basecoating both sides of the paper may provide a flatter and more balanced paper substrate.

[0141] Thus, the paper substrate may also be coated on the opposite back surface of the paper with a base coating composition comprising a polymer selected from the same group as the base coating on the upper surface of the paper.

[0142] Thus, there is provided a use of a paper substrate for a gas barrier material in a laminate packaging material for packaging oxygen-sensitive foods such as liquid, semi-liquid or viscous foods or water, wherein the paper substrate has a mass of 30 to 100 g / m2 measured in accordance with ISO 536:2012. 2) a machine direction breaking strain of more than 3% measured according to ISO 1924-3:2005, and a Benzene surface roughness on at least one side of less than 150 ml / min measured according to ISO 8791-2:2013, wherein the paper substrate is impregnated or base coated with a polymer selected from the group consisting of, for example, polyvinyl alcohol, PVOH, ethylene vinyl alcohol, EVOH, starch, starch derivatives, carboxymethyl cellulose, CMC, or other cellulose ethers.

[0143] The amount of impregnating polymer or base coat polymer is 0.5 to 4 g / m2 on a dry basis. 2 , e.g., 0.5 to 3 g / m 2 , for example, 0.5 to 2 g / m 2 , for example, 0.5 to 1.5 g / m 2 It could be.

[0144] In another embodiment, the base coating composition may comprise a polymeric binder having a Tg of -3°C or less, such as -10°C or less, for example -15°C or less, for example -20°C or less. The polymeric binder may be an acrylic or methacrylic homopolymer or copolymer. Other suitable polymeric binders in coating compositions for stretchable paper and paperboard applications may be polyurethane-based binders, vinyl acetate-based binders, and polyester resins with a Tg<-3°C.

[0145] The base coating composition may further comprise an inorganic filler selected from the group consisting of calcium carbonate-containing materials, talc, kaolin, clay, titanium dioxide, satin white, bentonite, and mixtures thereof. In one embodiment, the inorganic filler is selected from the group consisting of calcium carbonate-containing materials, clay, kaolin, and mixtures thereof.

[0146] The purpose of the base coating is to provide a smoother surface to the paper substrate by forming a better adhesive bridge to the paper substrate at increased machine direction breaking strain and / or to improve the quality of further coatings or layers applied over the base coated surface.

[0147] The base coating can be applied by a suitable aqueous dispersion coating method, followed by drying to evaporate the water. The base coated and dried substrate can then be subjected to calendering.

[0148] There is a clear difference between impregnation and coating with similar polymer compositions. Impregnation, which is primarily performed to place the polymer composition inside the paper, i.e., below the surface, is accomplished by applying a wet polymer composition and subsequently or simultaneously applying pressure to the wet-coated surface. Coating with the same or similar polymer compositions is accomplished by wet-coating and direct drying while the paper substrate web is running at high speed to prevent the wet-coated polymer composition from absorbing liquid rather than evaporating. The goal is to provide a continuous, substantially uninterrupted, and completely covered coating that extends across the entire surface of the substrate. While not completely perfect, such a base coating provides a good base or foundation for the subsequent application of a thin, but continuous, more complete, and uninterrupted gas barrier coating. While impregnation and base coating can impart improved substrate properties to paper substrates in different ways, they have been found to produce similar improvements in subsequently applied gas barrier coatings. A continuous, uninterrupted gas barrier coating is crucial for the gas barrier properties of coatings in laminate materials. Even if it is very thin, the required gas barrier properties will last for a long time as long as it is free from defects such as pinholes and cracks. A paper substrate that is only impregnated may need to have more gas barrier coatings applied to it in order to obtain good gas barrier properties, whereas a base-coated paper substrate can then have a thinner gas barrier coating applied to it. On the other hand, the quality of the base coating may need to be somewhat different, for example, by including some inorganic particles or by having a high viscosity during wet application.

[0149] A gas-barrier coated paper substrate for gas-barrier materials in laminate packaging materials for oxygen-sensitive products may be provided by using any one of the above-described embodiments of the paper substrate of the first aspect of the present invention, having applied to its upper surface at least one coating of at least one gas-barrier material, with a total coating thickness of 2 to 5000 nm, for example 2 to 4000 nm. Such thin coatings do not generate rejects or waste when used laminate packaging materials containing such coatings are recycled in existing cellulose fiber recycling streams, and furthermore do not consume significant material compared to the benefits such coatings provide.

[0150] At least one gas barrier coating may be formed by coating a dispersion or solution of an aqueous composition of at least one gas barrier material, followed by drying. The gas barrier coating forms a continuous, uninterrupted layer of the gas barrier material on the surface of the paper substrate. This is facilitated by the paper substrate being impregnated or base-coated with an impregnating or base-coating polymeric material composition. The impregnated or base-coated paper substrate has a smoother and / or closed surface, and the subsequently applied gas barrier coating can be applied at a much lower thickness, while still maintaining high coating quality, achieving a uniform surface and thickness and exhibiting homogeneity throughout the thickness and lateral extension of the continuous coating layer.

[0151] According to one embodiment, the upper surface of the paper substrate may be coated with a gas barrier material comprising a polymer to a dry coating thickness of 100-5000 nm (0.1-5 μm), such as 100-4000 nm (0.1-4 μm), for example 300-3500 nm (0.3-3.5 μm), for example 300-2500 nm (0.3-2.5 μm).

[0152] The gas barrier material may comprise a polymer selected from the group consisting of a vinyl alcohol polymer or copolymer, such as polyvinyl alcohol, PVOH, or ethylene vinyl alcohol, EVOH, and a polysaccharide or polysaccharide derivative. Suitable polysaccharides or polysaccharide derivatives may be selected from the group consisting of starch, starch derivatives, chitosan, chitosan derivatives, cellulose, cellulose derivatives, and lignocellulosic compounds. In one embodiment, the polymer is of renewable (i.e., non-fossil-based) origin.

[0153] In more specific embodiments, the gas barrier material 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, NNC, and blends of two or more thereof.

[0154] According to another embodiment, the gas barrier material may be a water-dispersible polyamide or polyester, or polyvinylidene chloride. Preferably, such water-dispersible polyamide, polyester, or polyvinylidene chloride is bio-based and / or can be applied at very low coating weights, i.e., less than 1 g / m 2 It is possible to provide oxygen gas barrier properties with only a very thin coating amount, such as less than 1.5 μm, the aim being to provide a gas barrier material that can be recycled in the cellulose fiber recycling stream without leaving behind undesirable amounts of waste, i.e., so-called "rejected material."

[0155] Such thin coatings are obtained by dispersion or solution coating of the gas barrier material contained in the aqueous gas barrier composition, followed by drying, and cannot be applied at thin coating thicknesses by alternative methods such as extrusion coating. While polymers and materials can also be applied as solutions or dispersions in organic solvents other than water, such methods are generally not suitable for providing environmentally sustainable packaging materials of the future.

[0156] In a preferred embodiment, the amount is 0.5 to 3.5 g / m 2 , e.g., 1 to 3 g / m 2 A coating of PVOH is applied to the top side of the paper substrate.

[0157] Furthermore, when the gas barrier material coating is formed by coating a dispersion or solution of the gas barrier composition and then drying, it may further comprise a layered compound such as nano-dimensional layered clay, talcum, or CaCO3.

[0158] Thus, there may be provided a gas barrier coated paper substrate for use in a laminate packaging material for packaging of oxygen sensitive foods such as liquid, semi-liquid or viscous foods or water, the paper substrate having a gas barrier coating weight of 30 to 100 g / m2 measured in accordance with ISO 536:2012. 2 , a machine direction breaking strain of more than 3% measured according to ISO 1924-3:2005, a Bendtsen surface roughness of at least one side of less than 150 ml / min measured according to ISO 8791-2:2013, and the paper substrate is impregnated or base coated in a first step with a polymer selected from the group consisting of polyvinyl alcohol, PVOH, ethylene vinyl alcohol, EVOH, starch, starch derivatives, carboxymethyl cellulose, CMC, or other cellulose ethers.

[0159] Preferably, the impregnating or basecoat polymer is selected from starch, starch derivatives, carboxymethyl cellulose, CMC, or other cellulose ethers, and has a dry weight of 0.5 to 4 g / m2 , e.g., 0.5 to 3 g / m 2 , for example, 0.5 to 2 g / m 2 , for example, 0.5 to 1.5 g / m 2 A gas barrier coating may then be applied on top of the impregnated or base coated paper as a continuous, uninterrupted coating to a total thickness of 2 to 4000 nm (4 μm), for example 2 to 3000 nm (3 μm).

[0160] According to another embodiment, the gas barrier coated paper substrate has on its upper surface a vapor deposition coating of a gas barrier material selected from metals, metal oxides, inorganic oxides, and amorphous diamond-like carbon coatings. More specifically, the vapor deposition coating may be selected from the group consisting of aluminum vapor deposition coatings and aluminum oxide (AlOx). Preferably, the vapor deposition coating is aluminum.

[0161] In a further embodiment, the gas barrier coated paper substrate further comprises a first continuous coating of a gas barrier material on its upper surface formed by coating a dispersion or solution of the aqueous gas barrier composition and subsequent drying, and a vapor deposition coating of a gas barrier material selected from metals, metal oxides, inorganic oxides, and amorphous diamond-like carbon applied to the first coating. The coated paper substrate thus provided with the gas barrier material coating is then further coated by vapor deposition to a thickness of 2 to 200 nm, for example, 2 to 150 nm, for example, 2 to 100 nm, for example, 5 to 80 nm, for example, 5 to 50 nm, for example, 2 to 45 nm.

[0162] There may further be provided a coated paper substrate, wherein the back side of the paper substrate is also coated with at least one coating of at least one gas barrier material as defined in any of the above embodiments.

[0163] The vapor-deposited barrier coating that is ultimately coated on top of the paper substrate is applied by physical vapor deposition (PVD) or chemical vapor deposition (CVD), such as plasma-enhanced chemical vapor deposition (PECVD).

[0164] 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-deposited coating, the barrier coating may be less flexible, more susceptible to cracking when applied to flexible substrates, and more expensive.

[0165] Other examples of vapor-deposited coatings include aluminum oxide (AlOx, Al2O3) and silicon oxide (SiOx) coatings. Generally, PVD coatings of such oxides may not be well suited for incorporation into packaging materials by lamination, but metallized layers produced by PVD are well suited for flexible packaging laminates.

[0166] Typically, vapor deposited aluminum layers have a thin surface portion that consists essentially of aluminum oxide due to the nature of the metal coating process used.

[0167] In one embodiment, such an aluminum vapor-deposited layer is applied to an optical density (OD) of 1.8 to 3.5, preferably 1.9 to 2.5. If the optical density is lower than 1.8, the barrier properties of the metal vapor-deposited film may be too low. On the other hand, if the metal thickness is too thick, the metal vapor-deposited layer becomes brittle, and the heat load during long-term deposition of the substrate film increases, resulting in low heat resistance during the metal vapor deposition process. This may adversely affect the quality and adhesion of the coating. In one embodiment, with regard to the flexibility and coating operation efficiency of the applied metal vapor-deposited coating, the metal vapor-deposited coating is applied to a thickness of 10 to 200 nm, e.g., 10 to 150 nm, e.g., 10 to 100 nm, e.g., 10 to 95 nm, e.g., 10 to 80 nm, e.g., 10 to 50 nm, which corresponds to less than 1 to 3% of the aluminum metal material present in aluminum foil of conventional packaging thicknesses, such as 6 to 9 μm.

[0168] Other coatings may be applied by plasma-enhanced chemical vapor deposition (PECVD), which involves depositing vapors of compounds onto a substrate in a more or less oxidizing environment. For example, silicon oxide coatings (SiOx) may also be applied by PECVD processes, and can achieve very good barrier properties under certain coating conditions and gas recipes.

[0169] DLC defines a type of amorphous carbon material (diamond-like carbon) that exhibits some of the typical properties of diamond. Preferably, hydrocarbon gases such as acetylene or methane are used as the process gas for the plasma to produce the amorphous hydrogenated carbon barrier layer coating, i.e., DLC, applied by the PECVD vacuum process. DLC coatings by PECVD under vacuum provide good adhesion to adjacent polymer layers and adhesive layers in laminate packaging materials. In particular, polyolefins, especially polyethylene and polyethylene-based copolymers, provide good adhesion to adjacent polymer layers.

[0170] The total applied thickness of the continuously coated gas barrier coating may be up to 5 μm, such as 4 μm, for example 3.5 μm.

[0171] A laminate packaging material of the third aspect, for example for packaging oxygen-sensitive products such as liquid, semi-liquid and viscous foods or water, e.g., oxygen-sensitive foods, comprises a paper substrate as defined in any one of the embodiments of the first use aspect or a barrier-coated paper substrate according to any one of the embodiments of the second aspect, and further comprises a bulk layer of paper, paperboard or other cellulosic material, a first outermost layer of liquid-tight material and a second innermost layer of liquid-tight material, which second innermost layer may further be a liquid-tight, heat-sealable material.

[0172] Thus, the laminate packaging material further comprises a bulk layer of paper, paperboard or other cellulosic material, with a paper substrate or gas barrier coated paper substrate laminated between the bulk layer and the second innermost layer facing the interior of the container formed from the laminate packaging material.

[0173] When a substrate is coated with a vapor deposition coating, the coated paper substrate typically also has additional water vapor barrier properties, eliminating the need for additional layers of gas or water vapor barrier material in the overall laminate structure.

[0174] When the upper surface of a paper substrate has a first coating of a gas barrier material formed by applying and then drying a dispersion or solution of an aqueous gas barrier composition such as PVOH, and further has a vapor-deposited coating of a gas barrier material selected from metals, metal oxides, inorganic oxides, and amorphous diamond-like carbon, applying a vapor-deposited coating of a gas barrier material selected from metals, metal oxides, inorganic oxides, and amorphous diamond-like carbon, such as an aluminum vapor-deposited coating, on top of the first coating, results in a very good material that can be used as the sole oxygen barrier material in laminate packaging materials instead of conventional aluminum foils with a thickness of more than 5 μm, e.g., 6 μm. The vapor-deposited coating or metal vapor-deposited coating thus applied may, of course, be further coated with another wet-applied coating or a vapor-deposited coating of the same or different chemistry to further improve the barrier properties, but this is not required and may further increase costs.

[0175] In a further embodiment, the paper substrate, or coated paper substrate, comprises a binder selected from the group consisting of acrylic polymers and copolymers, starch, starch derivatives, cellulose derivatives, polymers and copolymers of vinyl acetate, copolymers of vinyl alcohol, and copolymers of styrene-acrylic latex or styrene-butadiene latex, at a concentration of 0.5 to 5 g / m 2 The intermediate binder composition can be laminated to the bulk layer by coating with an intermediate binder composition containing a small amount of the intermediate binder composition. Such a small amount of the intermediate binder composition can only be applied by aqueous dispersion or solution coating of the polymer binder, and cannot be applied by extrusion coating or extrusion lamination of a polymer melt. In such wet lamination, since the surfaces of the layers to be bonded are both made of cellulose, the aqueous medium is absorbed into each cellulose layer, forming a thin, dry adhesive layer at the interface between the two layers.

[0176] To improve the mechanical robustness of laminate packaging materials, prefabricated polymer films may be laminated between the paper or coated paper substrate and the innermost second liquid-tight material layer. Prefabricated films have different mechanical properties than simply extrusion-coated or extrusion-laminated layers of the same or corresponding polymers due to the higher orientation of the polymers that make up the film. Therefore, incorporating such films into the structure can make the laminated material stronger overall and more resistant to any downstream toughening processing. Prefabricated films are preferably not used in materials because they increase costs both in terms of material procurement and lamination. Prefabricated films can have different mechanical properties, ranging from the tough, biaxially oriented films obtained by simple extrusion-cast film to films produced by film-blowing, which have inherent polymer orientation or subsequent additional orientation. However, it is preferable to use polymer materials that are simply extrusion-coated or extrusion-laminated.

[0177] The second, innermost layer of liquid-tight, heat-sealable material can be a polyolefin, preferably a blend of low-density polyethylene (LDPE) and metallocene-catalyzed linear low-density polyethylene (m-LLDPE). This type of polymer offers the best balance of liquid-tightness and heat-sealability and is the type of polymer most commonly used for innermost layers today to maximize package integrity in heat-sealed packaging containers. Careful selection of the composition of this layer allows for the amount of polymer in this layer to be optimized to be as low as possible while still producing a durable, reliable package filled with product.

[0178] In one embodiment, the second, innermost, liquid-tight, heat-sealable material layer may be or may comprise a pre-fabricated 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.

[0179] In certain embodiments, the laminate packaging material may have a prefabricated polymeric film substrate laminated to the inside of a paper substrate or coated paper substrate, i.e., on the side of the paper substrate opposite the side laminated to the bulk layer, the prefabricated polymeric film substrate having a vapor-deposited coating of a gas barrier material selected from metals, metal oxides, inorganic oxides, and amorphous diamond-like carbon coatings.

[0180] According to different specific embodiments, the laminate packaging material may have a pre-fabricated polymer film substrate laminated to the inner side of a paper substrate or a coated paper substrate, i.e., the side of the paper substrate opposite to the side laminated to the bulk layer, and the pre-fabricated polymer film is filled with an inorganic layered compound to impart gas and vapor barrier properties to the polymer film.

[0181] According to yet another specific embodiment, the laminate packaging material may have a pre-fabricated polymer film substrate laminated to the inside of a paper substrate or a coated paper substrate, i.e., on the side of the paper substrate opposite to the side to be laminated with the bulk layer. The pre-fabricated polymer film is coated with a gas barrier material obtained by dispersing or solving the gas barrier material composition to a dry coating thickness of 100 to 4000 nm (0.1 to 4 μm), for example, 300 to 3500 nm (0.3 to 3.5 μm), for example, 300 to 2500 nm (0.3 to 2.5 μm), and then dried.

[0182] An objective of any one of the aforementioned specific embodiments is to add complementary properties to laminate packaging materials when a paper substrate itself is used as the gas barrier material in the laminate structure, when a coated paper substrate is used, when an applied coating only provides partial gas barrier properties, or when the coating only has a moisture-sensitive gas barrier material. By laminating the coated paper substrate to a polymer film that also adds moisture-resistant oxygen barrier properties, or at least water vapor barrier properties, the at least two different gas barrier materials can interact to provide enhanced overall barrier properties to the entire laminate structure. The necessary adhesive layer between the paper substrate and the additional barrier film ensures these enhanced barrier properties, and adjacent adhesive layers can promote them to a synergistic level by acting as additional "gas and vapor migration stoppers" in the laminate structure.

[0183] The film may comprise a heat-sealable layer, may be completely heat-sealable, or may form or be part of the innermost heat-sealable layer.

[0184] The outermost and innermost liquid-tight and laminate layers within a laminate structure typically do not provide a high barrier to migrating gas molecules or small molecules. Their purpose is to directly prevent water and other liquids from penetrating the cellulosic bulk material or other paper layers. Liquid barrier layers also prevent water vapor from migrating enough to wet the cellulose, but they cannot maintain the moisture content of the laminate structure at zero or the low moisture content of "dry" paper (approximately 7-8% at ambient temperature, i.e., 23°C and 50% relative humidity). The moisture content of laminate carton materials for liquid-filled packaging containers is typically quite high, and migration through the material will occur unless an additional moisture vapor barrier is included, such as aluminum foil, a metallized layer, other vapor-deposited coatings, an inorganic material layer, or another polymeric material layer.

[0185] In any of the above-listed embodiments including a prefabricated film, the prefabricated polymer film may comprise a polymer selected from any one of polypropylene, polyethylene, blends thereof, and copolymers of ethylene and propylene, and optionally an additional comonomer. According to further embodiments, the prefabricated polymer film may comprise a polymer selected from high density polyethylene or linear low density polyethylene.

[0186] As described in any one of the above alternatives, there may be an additional extrusion coated layer or multi-layer portion of an innermost heat-sealable, liquid-tight polymer inside the pre-fabricated film. Such heat-sealable thermoplastic polymer may also, or alternatively, form part of the pre-fabricated film.

[0187] The paper or paperboard bulk layer used in the present invention typically has a thickness of about 100 μm to about 600 μm and a weight of about 100 to 500 g / m 2 , preferably about 200 to 300 g / m 2 The bulk layer of the laminated packaging material of the present invention may be a conventional paper or paperboard substrate having a surface weight of 1000 psi or less and of suitable packaging quality. The bulk layer of the conventional paper or paperboard has a MD breaking strain of less than 3% and is therefore not stretchable. The purpose of the bulk layer in the laminated packaging material of the present invention is to provide dimensional stability, stiffness, and rigidity to the packaging container, for example, for use under wet and humid conditions and / or for storage of liquids and wet (heavy) foods. On the other hand, a thin, stretchable paper substrate has a machine direction breaking strain of more than 3% and provides a suitable carrier layer for thin, delicate gas barrier coatings to enhance the gas barrier properties of such packaging containers.

[0188] For low-cost, long-term packaging of liquid foods in a sterile manner, thinner packaging laminates with thinner paper core layers can be used. Packages made from such packaging laminates resemble pillow-shaped flexible pouches rather than collapsible ones. Paper suitable for such pouch packaging is typically about 50 to about 140 g / m2 , preferably about 70 to about 120 g / m 2 , more preferably about 70 to about 110 g / m 2 has a surface weight of

[0189] The paper substrate may be bonded to the bulk layer by an intermediate adhesive or thermoplastic polymer bonding layer, thus bonding the uncoated surface of the barrier-coated paper to the bulk layer. According to one embodiment, the bonding layer is a polyolefin layer, for example, a layer of a polyethylene-based polyolefin copolymer or blend, particularly a layer containing a majority of ethylene monomer units. The bonding layer may be bonded to the barrier-coated cellulose-based substrate by melt-extrusion laminating the bonding polymer layer between a web of the bulk layer and a web of the cellulose-based substrate, and simultaneously pressing the three layers together while advancing through a laminating roller nip, thus providing a laminate structure by extrusion lamination.

[0190] In another embodiment, a barrier-coated cellulose-based substrate can be bonded to the bulk layer by wet-laminating an aqueous dispersion of an adhesive composition containing an adhesive polymer binder onto one of the web surfaces to be laminated and then pressing the two paper webs together while advancing them through a laminating roller nip, thus providing a laminate structure. The moisture in 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 process. Therefore, a forced drying step is unnecessary. The adhesive polymer binder is selected from the group consisting of acrylic polymers and copolymers, starch, cellulose and polysaccharide derivatives, and polymers and copolymers of vinyl acetate and vinyl alcohol. For the best environmental and sustainability profile, adhesive binders derived from plants or non-fossil sources are preferred.

[0191] Suitable thermoplastics for the outermost and innermost liquid-tight layers are polyolefins such as homopolymers or copolymers of polyethylene and polypropylene, preferably polyethylene, and 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. According to one embodiment, the outermost liquid-tight layer is LDPE, and the innermost heat-sealable liquid-tight layer is a blend composition of m-LLDPE and LDPE to obtain optimal lamination and heat-sealing properties.

[0192] The same thermoplastic polyolefin-based materials, particularly polyethylene, listed for the outermost and innermost layers are also suitable for adhesive layers within the laminate material, i.e., between a bulk or core layer, such as paper or paperboard, and a further barrier film or sheet. In one embodiment, the thermoplastic adhesive layer may be a simpler or more conventional polyethylene layer, such as a low-density polyethylene (LDPE) layer.

[0193] Although polyethylene-based polymers have been used and optimized for a very long time in the field of liquid carton packaging materials, thermoplastic polymer materials, such as other polyolefins, e.g., other polyethylenes or polypropylenes, or other liquid-tight materials, such as polyesters, to further impart heat-sealability and thermal processability, are considered within the scope of the present invention. Thus, any kind of bio-based such thermoplastic material is considered within the scope of the present invention, as long as a separate gas barrier property must still be provided via the materials described in connection with the use of the present invention, the stretchable paper substrate, and the barrier-coated stretchable paper substrate.

[0194] In a further embodiment, the second innermost liquid-tight heat-sealable polyolefin layer is a pre-fabricated film made of the same or similar polyolefin as described above, in order to improve the mechanical robustness of the packaging material. Due to the manufacturing process in the film blowing and film casting operations, and optionally the subsequent film orientation operation process, the polymer of such a film acquires properties different from those possible from the (co)extrusion coated polyolefin layer. Therefore, such a pre-fabricated polymer film can contribute to the mechanical robustness of the laminate packaging material, and the mechanical strength and packaging integrity of the packaging container formed and filled from the laminate packaging material.

[0195] According to a further embodiment, suitable adhesive or tie layers within the laminate material, for example between a bulk or core layer and a barrier coated paper substrate, or between an innermost liquid-tight heat-sealable layer and a paper substrate, include: The adhesive thermoplastic polymer may be, for example, a modified polyolefin based mainly on LDPE or LLDPE copolymers, or a graft copolymer having a functional group-containing monomer unit, such as a carboxyl functional group or a glycidyl functional group, such as a (meth)acrylic acid monomer or a maleic anhydride monomer (i.e., ethylene acrylic acid copolymer (EAA) or ethylene methacrylic acid copolymer (MAH)). For example, a (meth)acrylic acid monomer or a maleic anhydride (MAH) monomer (i.e., ethylene acrylic acid copolymer (EAA) or ethylene methacrylic acid copolymer (EMAA)), an ethylene-glycidyl (meth)acrylate copolymer (EG(M)A), or an MAH-grafted polyethylene (MAH-g-PE). Another example of such a modified or adhesive polymer is a so-called ionomer or ionomeric polymer. Preferably, the modified polyolefin is an ethylene acrylic acid copolymer (EAA) or ethylene methacrylic acid copolymer (EMAA).

[0196] The laminate packaging material produced as described above provides good adhesion between adjacent layers within the laminate structure, and good quality of each and every barrier coating and barrier pre-coating, thereby providing good integrity when converted into a filled packaging container. In particular, for packaging liquids and moist foods, it is important that the interlayer adhesion within the laminate packaging material is maintained even under moist packaging conditions, as is the oxygen gas barrier property.

[0197] According to further embodiments, a packaging container formed from the laminated packaging material can be partially sealed, filled with a liquid or semi-liquid food product, and then sealed by sealing the packaging material to itself, optionally in combination with a plastic opening or top of the package.

[0198] In conclusion, the use of a paper substrate further coated with a barrier layer or laminated to a further barrier material layer in the laminate packaging material defined by this invention results in a robust and reliable package for packaging shelf-stable liquid foods, with the improved properties provided by the paper substrate itself. The laminate packaging material structure works well for formation into a foldable package, both due to the improved interaction and adhesion between the paper substrate and the gas barrier material coating, and the improved contribution to gas barrier properties by the paper substrate itself, such as when the paper substrate is a stretchable paper substrate.

[0199] ( Examples and Description of the Preferred Embodiments Preferred embodiments of the present invention will now be described with reference to the drawings. [Brief explanation of the drawings]

[0200] [Figure 1a] 1 is a cross-sectional view showing a schematic representation of an embodiment of a stretchable paper substrate for use according to the present invention; FIG. [Figure 1b] 1 is a cross-sectional view showing a schematic representation of an embodiment of a stretchable paper substrate for use according to the present invention; FIG. [Figure 1c] 1 shows SEM images of the surface and cross section of a paper substrate of the present invention. [Figure 1d] 1 is a SEM image of the surface and cross section of a paper substrate of the present invention. [Figure 1e] 1 is a SEM image of the surface and cross section of a paper substrate of the present invention. [Figure 2a] 1 is a cross-sectional view schematically illustrating an alternative embodiment of the stretchable paper substrate of the present invention. [Figure 2b] 1 is a cross-sectional view schematically illustrating an alternative embodiment of the stretchable paper substrate of the present invention. [Figure 3a] 1 is a schematic cross-sectional view of a gas barrier coated paper substrate of the present invention. [Figure 3b] 1 is a schematic cross-sectional view of a gas barrier coated paper substrate of the present invention. [Figure 3c] 1 is a schematic cross-sectional view of a gas barrier coated paper substrate of the present invention. [Figure 4a] 1a-1b and 2a-2b show laminated packaging materials of the present invention comprising the barrier-coated paper substrate embodiments of FIGS. 1a-1b and 2a-2b. [Figure 4b] 1a-1b and 2a-2b show laminated packaging materials of the present invention comprising the barrier-coated paper substrate embodiments of FIGS. 1a-1b and 2a-2b. [Figure 5] FIG. 3c shows a further embodiment of a laminate packaging material of the present invention comprising a barrier-coated paper substrate according to FIG. 3c or FIG. 1a or FIG. 1b. [Figure 6a] FIG. 1 is a schematic diagram showing a method for dispersion coating a gas barrier coating composition onto a cellulose-based substrate. [Figure 6b] FIG. 1 is a schematic diagram illustrating a method for melt (co)extrusion coating a layer of a thermoplastic, heat-sealable, liquid-tight polymer onto a web substrate to form the innermost and outermost layers of the packaging laminate of the present invention. [Figure 7a] FIG. 1 is a perspective view of a plant for physical vapor deposition (PVD) coating of a web substrate using solid metal evaporation flakes. [Figure 7b] FIG. 1 is a perspective view of a plant for plasma-enhanced chemical vapor deposition (PECVD) coating of paper substrates or films by magnetron plasma; [Figure 8a] 1 is a diagram showing a typical example of a packaging container manufactured from the laminate packaging material of the present invention. [Figure 8b] 1 is a diagram showing a typical example of a packaging container manufactured from the laminate packaging material of the present invention. [Figure 8c] 1 is a diagram showing a typical example of a packaging container manufactured from the laminate packaging material of the present invention. [Figure 8d] 1 is a diagram showing a typical example of a packaging container manufactured from the laminate packaging material of the present invention. [Figure 9] Figure 1 shows how packaging containers are manufactured from packaging laminate in a continuous roll-fed, form-fill-seal process. DETAILED DESCRIPTION OF THE INVENTION

[0201] Example Example 1 of the invention

[0202] Inventive Example 1A :Paper substrate manufacturing Two pulps were provided: i) ECF bleached kraft pulp from softwood (pine and spruce mix), and ii) ECF bleached kraft pulp from hardwood (e.g., birch).

[0203] Softwood pulp was refined in a high-consistency (HC) refiner at a specific energy of 200 kWh / ton (net energy input per ton of dry fiber). The HC-refined pulp was then mixed in a mixing chest with broken pulp, a blend of bleached softwood and hardwood pulps (the majority of the broken pulp was obtained from the same paper mill). The broken pulp content of this softwood-based blend was 10%. This softwood-based blend was then refined in a low-consistency (LC) refiner at a specific energy of 80–85 kWh / ton. The LC refinery resulted in a Schopper-Riegler (°SR) of ~26°SR according to ISO 5267-1:1999.

[0204] Hardwood pulp was mixed separately with the same type of broken wood and refined at a low consistency with a specific energy of 90 kWh / ton. Broken wood accounted for 20% of the hardwood-based blend. The LC refined hardwood-based blend achieved a Schopper-Riegler (°SR) value of ~44°SR.

[0205] Papermaking chemicals were added to each of the two fiber streams (4 kg / tonne cationic starch, 0.2 kg / tonne silica, 1.5 kg / tonne rosin size, and 2.2 kg / tonne alum). The softwood-based mix was pumped to the bottom ply headbox of a two-ply Fourdrinier machine, and the hardwood-based mix was pumped to the top ply headbox of the same Fourdrinier machine. The dry mass flow rates through each headbox were similar, with the bottom ply (33 g / m²) being the largest. 2 ) and top layer (30g / m 2 ) and the total weight before coating is 63g / m 2 The vertical slice lip was 33 mm at the bottom ply headbox and 18.5 mm at the top ply headbox, indicating relatively low headbox consistencies (approximately 0.14% at the bottom ply and 0.25% at the top ply). The wire speed was 608 m / min. On a paper machine specifically designed for this product, wire speeds can be significantly higher.

[0206] The two layers formed in the Fourdrinier press were coupled at a dryness of ~10% and then further dewatered to a dryness of ~20% using a vacuum foil box before being wet-pressed in a press section with two single-felt press nips: the first press had a felt on the top side and the second press had a felt on the bottom side.

[0207] After the wet press, the web was dried in a pre-drying section to a dryness of ~65% and then entered the stretching unit. The stretching unit, a double-roll compactor type commonly referred to as an "Expanda," was operated at an inlet web speed of ~638 m / min and an outlet web speed of ~581 m / min. As a result, the paper web was compressed in the machine direction (the paper web "shortened" by approximately 9%), increasing the breaking strain value ("extensibility") of the final paper. The drive group after the stretching unit was operated at a slightly increased speed, resulting in a decrease in the MD breaking strain value. Immediately after the stretching unit, the paper web was dried in a post-drying section with conventional steam-heated cylinders to form a paper substrate with a moisture content of ~6%.

[0208] Inventive Example 1B: Impregnation The paper substrate of Inventive Example 1A was off-line impregnated from both sides with an aqueous polyvinyl alcohol (PVOH) composition in a conventional film press. The type of PVOH was Poval 10 / 98 (Kuraray), and its concentration in the composition was 10%. The composition also contained glyoxal (Cartabond TSI) in an amount of 6% by weight based on the amount of PVOH. The glyoxal acted as a crosslinking agent. The viscosity of the composition was 74 mPa·s (measured at 60°C). The applied amount of PVOH was 1 g / m² on the top surface. 2 , 2g / m on the back / bottom 2 The reason for using more PVOH on the back / bottom surface was that the pulp used to form the bottom layer had a lower SR value (hence the back / bottom surface was less dense than the top surface). The PVOH-impregnated paper substrate was dried with hot air to a moisture content of approximately 8%. The properties of the dried PVOH-impregnated paper substrate are shown below (Table 1).

[0209] Inventive Example 1C :Super calendar processing The saturated paper substrate of Inventive Example 1B was rewetted to 15%. The rewetted paper was fed into a pilot offline multi-nip calender (12 nips), also known as a supercalender. Supercalendering was performed using a thermo roll surface temperature of 140°C, achieved by an external induction heater, to obtain a stretchy, high-density paper. The line load at each nip was 360 kN / m (simulating 400 kN / m in actual production), and the speed was 360 m / min (simulating 400 m / min in actual production). The total supercalendering nip impulse was approximately 720 kPa·s [# nip × line load / web speed]. Heat from the thermo roll dried the stretchy, high-density paper. The moisture content at rewind was 5.5%. The properties of the stretchy, high-density paper are shown below (Table 1).

[0210] Comparative Example 1 This comparative example is not published prior art and forms part of a co-pending patent application.

[0211] Comparative Example 1A: Preparation of paper substrate (two-ply paper) Two pulps were provided: i) ECF bleached kraft pulp from softwood (pine and spruce mix), and ii) ECF bleached kraft pulp from hardwood (e.g. birch).

[0212] Softwood pulp was refined using a high consistency (HC) refiner with a specific energy of 225 kWh / ton (net energy input per ton of dry fiber). The HC refined pulp was then mixed in a mixing chest with broken pulp, which contained a blend of bleached softwood and hardwood pulps (the majority of the broken pulp was obtained from the same paper mill). The broken pulp content of this softwood-based mixture was 30%. This softwood-based mixture was then subjected to low consistency (LC) refining with a specific energy of 75 kWh / ton. The LC refinement resulted in a Schopper-Riegler (°SR) of ~30°SR according to ISO 5267-1:1999.

[0213] Hardwood pulp was mixed separately with the same type of broken wood and refined at a low concentration with a specific energy of 85 kWh / ton. The proportion of broken wood in the hardwood-based blend was 20%. The LC refined hardwood-based blend achieved a Schopper-Riegler (°SR) value of ~38°SR.

[0214] Papermaking chemicals were added to each of the two fiber streams (4 kg / tonne cationic starch, 0.2 kg / tonne silica, and 0.4 kg / tonne AKD). The softwood-based mixture was pumped into the bottom ply headbox of a two ply fourdrinier machine, and the hardwood-based mixture was pumped into the top ply headbox of the same fourdrinier machine. The dry mass flow rate through each headbox was the same, with a total weight of 60 g / m before coating. 2 (i.e., 30 g / m per layer) 2 ). The vertical slice lip was 34 mm at the bottom ply headbox and 16 mm at the top ply headbox, indicating relatively low headbox consistencies (approximately 0.12% at the bottom ply and 0.25% at the top ply). The wire speed was 600 m / min. On a paper machine specifically designed for this product, wire speeds can be significantly higher.

[0215] The two layers formed in the Fourdrinier press were coupled at ~10% dryness, further dewatered using a vacuum foil box to ~20% dryness, and then wet-pressed in a press section with two single-felt press nips: the first press had the felt on the top side, and the second press had the felt on the bottom side.

[0216] After wet pressing, the web was dried in a conventional multi-cylinder dryer to form a paper substrate with a moisture content of ~5%. Prior to winding, the paper substrate was calendered in a soft nip with a line load of 20 kN / m.

[0217] Comparative Example 1B: Impregnation A 1A paper substrate was impregnated offline on both sides with an aqueous polyvinyl alcohol (PVOH) composition in a conventional film press. The type of PVOH was Kuraray Poval 10 / 98, and its concentration in the composition was 10% (in another test, the concentration was instead 8%, which also gave good results). The composition also contained glyoxal (Cartabond TSI) in an amount of 6 wt% relative to the amount of PVOH. The glyoxal acted as a crosslinker. The viscosity of the composition was 74 mPa·s (measured at 60°C). The PVOH coating amount was 1 g / m² on the top surface. 2 , backside / bottom side is 2g / m 2 The reason for using more PVOH on the back / bottom surface was that the pulp used to form the bottom layer had a lower SR value (hence the back / bottom surface was less dense than the top surface). The PVOH-impregnated paper substrate was dried with hot air to a moisture content of 8%.

[0218] Comparative Example 1C: Supercalendered The 1B saturated paper was rewetted to 15%. The rewetted paper was fed into an offline multi-nip calender (12 nips) called a supercalender. Supercalendering was performed using a thermo roll surface temperature of 140°C, achieved by an external induction heater, to obtain high-density paper. The line load at each nip was 405 kN / m (simulating 450 kN / m in full-scale production). The total impulse through the supercalendering nip was ~800 kPa·s [# nip × line load / web speed]. Heat from the thermo roll dried the high-density paper. The moisture content at rewind was 8%. The properties of the resulting high-density paper are shown below (Table 1).

[0219] Comparative Example 2: Paper base material (single layer paper) This comparative example is not published prior art and forms part of a co-pending patent application.

[0220] Although the purpose was different, a single-ply paper having similar properties to the papers of Example 1 and Comparative Example 2 was produced using a similar manufacturing method. This single-ply paper was produced from a blend of kraft softwood pulp and kraft hardwood pulp with a small amount of CTMP pulp in a mixing ratio of 45:45:10. This single-ply paper was impregnated with polyvinyl alcohol from the top surface, and then subjected to a pressure of approximately 1050 kg / m. 3 and a density of 45g / m 2 The surface roughness of the upper surface was about 25 ml / min Bendtsen.

[0221] Comparative Example 3: Paper base material (single layer paper) A single-ply paper having the same composition as the paper base material of Comparative Example 2 was prepared. This single-ply paper was impregnated with polyvinyl alcohol from the upper surface, and had a strength of about 1100 kg / m 3 Calendered to a density of 57 g / m 2 The surface smoothness was less than 15 ml / min Bendtsen.

[0222] Test 1: Resulting properties of paper substrate The properties of the paper substrates used in Inventive Example 1 and Comparative Examples 1 to 3 are shown in Table 1 below. Table 1 also includes the paper physical properties of a commercially available greaseproof paper manufactured by Nordic Paper that was tested for the same purpose in prior art liquid carton packaging. Nordic Paper's Super Perga WS paper in Comparative Example 4 was used as a gas barrier paper substrate in International Application Publication WO2017 / 089508.

[0223] Regarding (Table 1): Basis weight is measured according to ISO 536:2019 and is expressed in g / m 2 Thickness was measured according to ISO 534:2011. Density was measured according to ISO 534:2011 and is expressed in kg / m 3Roughness refers to Bendtsen roughness and is measured in accordance with ISO 8791-2:2013 and is expressed in ml / min. Breaking strain was measured in the machine direction (MD) and / or cross direction (CD) according to ISO 1924-3:2005. Tensile strength index was measured in MD and CD according to ISO 1924-3:2005 and is expressed in Nm / g. Canadian Standard Freeness (CSF) is a measure of fiber drainability and is measured in ml according to ISO 5267-2:2001 using a Valmet HD400 pulper after repulping according to Valmet's repulping method, which is described in more detail below. °SR was measured according to ISO 5267-1:1999 after repulping according to ISO 5263-1:2004. Recyclability was measured according to PTS method PTS-RH 021 / 97. The recyclable fibres remaining after sieving the residue were reported. The oxygen transmission rate (OTR) was measured at 20 g / m² on the top surface of the paper. 2 After laminating with LDPE, measured according to ASTM F1927-14, units are cm 3 / m 2 / 24 hours, 0.2 atmospheres (21%) oxygen.

[0224] [Table 1]

[0225] § According to supplier datasheet # 1.5g / m per side 2 was tested on high density paper impregnated with PVOH * Basis weight: 32 g / m 2 instead of 38g / m 2 was ** Basis weight: 32 g / m 2 instead of 45g / m 2 was

[0226] Valmet's repulping process was carried out as follows: The paper was repulped using a Valmet HD400 pulper. Agitation was provided by an impeller with three radially serrated blades measuring 30 x 40 mm, rotating at a speed of 3000 rpm. The paper was cut into 90 x 90 mm pieces. 0.5 kg of air-dried paper pieces were mixed with 10 liters of water to a 5% consistency and repulped at 57°C for 2.5 minutes. Five liters of water were then added to a 3.3% consistency, and the repulping continued for a further 17.5 minutes at 57°C. The total repulping time was therefore 20 minutes.

[0227] Measurement of Canadian Standard Freeness of Pulp: Pulp obtained from the Valmet repulping process described above was diluted to ~0.3% and tested for Canadian Standard Freeness according to ISO 5267-2:2001.

[0228] As can be seen from Table 1, the paper substrate used in Example 1 of the present invention has very similar properties to the papers of Comparative Examples 1 to 3, except that the breaking strain in the MD direction is higher because the paper is compressed in the elongation unit during papermaking.

[0229] Test 2: Laminated material and packaging container

[0230] The paper substrates of Comparative Examples 1 and 2 were dispersed coated two more times with intermediate and subsequent drying operations to obtain a 3 g / m2 dispersion on the paper substrate. 2 A continuous, uninterrupted PVOH coating of 1000 ppm was applied. The PVOH coated paper substrate was further metallized to an optical density of about 2.

[0231] The paper substrate thus gas barrier coated was then coated with LDPE 20g / m 2was further coated on the metal vapor deposition coating, and the OTR was measured in the same manner as in Table 1. The OTR values ​​of the coated papers of Comparative Examples 1 and 2 measured under conditions of 23°C and 80% relative humidity (RH) were not significantly higher than the OTR values ​​measured under conditions of 23°C and 50% RH (for the barrier-coated substrate of Comparative Example 1, the OTR under both the 23 / 50 and 23 / 80 conditions was approximately 0.34 cm 3 / m 2 For Comparative Example 2, the OTR under the two conditions was 0.25 and 0.27 cm, respectively. 3 / m 2 / 24 hours, the pressure was 0.2 atmospheres, i.e., there was only a very small change within the margin of error).

[0232] The paper substrate used in Inventive Example 1 was also dispersion coated twice with intermediate and subsequent drying operations to provide a 3 g / m2 dispersion on the paper substrate. 2 The PVOH-coated paper substrate was further metallized to an optical density of about 2.2 and coated at 20 g / m² as above. 2 Again, there was no significant increase in OTR measured at 23°C and 80% RH compared to 23°C and 50% RH (OTR increased from 0.31 to 0.34 cm). 3 / m 2 / 24 hours, there was only a slight increase at 0.2 atmospheres (21%) oxygen).

[0233] It was thus concluded that the paper barrier material according to the invention has a low MD strain to failure and is less sensitive to high humidity conditions than similar, more recently developed, conventional, i.e. non-'elastic', paper barrier materials.

[0234] Next, laminated packaging materials comprising barrier-coated paper substrates according to Comparative Example 1 and Comparative Example 2 and Inventive Example 1 were produced according to the layer configurations.

[0235] / LDPE12g / m 2 / Paperboard 80mN / LDPE 15 or 20g / m 2 / Paper base + PVOH + Metal vapor deposition / Adhesive EAA copolymer 6g / m 2 +19 or 29 g / m 2 Blend of LDPE+mLLDPE /

[0236] 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 offers the flexibility to quickly change between different package formats. The packages were in the Tetra Brik® format with a capacity of 200 ml.

[0237] During the test, no major issues were identified with the package's integrity (the tightness of the packaging against the surrounding environment) or seal performance, and it was deemed a success.

[0238] The oxygen transmission rate of flat packaging materials was measured using a coulometric detector according to ASTM standard F1927-14. Moisture levels were 50% or 80% relative humidity. Units are cm 3 / m 2 For a 24-hour period, the oxygen pressure can be selected to be 0.2 atmospheres or 1 atmosphere. To make the OTR values ​​measured at 1 atmosphere and 0.2 atmospheres comparable, the former values ​​can be multiplied by 0.2.

[0239] The oxygen transmission rate of packaging materials (filled, empty, dry) was measured at 0.2 atmospheres (ambient air contains 21% oxygen) according to ASTM standard F1307-14. The unit is cm 3 / Package / 24 hours.

[0240] The package is mounted in a special holder, the inside of which is purged with nitrogen, and the outside of which is exposed to the environment surrounding the device. As oxygen permeates through the package 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.

[0241] To prepare Comparative Examples 4-1 and 4-2 (prior art and reference examples of laminate packaging materials), Nordic Paper's 32 g / m 2 Greaseproof paper Super Perga® WS (38 g / m 2 Super Perga® WS from (Table 3) was used in Comparative Example 6).

[0242] The properties of the laminate packaging material are shown below (Table 2).

[0243] [Table 2]

[0244] * / LDPE12g / m 2 / Paperboard 260mN / LDPE 20g / m 2 / Paper base + PVOH + Metal deposition / LDPE 20g / m 2 / LDPE+mLLDPE20g / m 2 / LDPE20g / m 2 / ** / LDPE12g / m 2 / Paperboard 80mN / LDPE 20g / m 2 / Paper base + PVOH + Metal deposition / LDPE 40g / m 2 / *** / LDPE12g / m 2 / Paperboard 80mN / LDPE 20g / m 2 / Paper base + PVOH + Metal vapor deposition / Adhesive EAA copolymer 6g / m 2 +29g / m 2 Blend LDPE+mLLDPE / **** / LDPE 12g / m2 / Paperboard 80mN / LDPE 15g / m2 / Paper base + PVOH + Metal vapor deposition / Adhesive EAA copolymer 6g / m2 + 19g / m2 Blended LDPE + mLLDPE /

[0245] The difference between the comparative example and the example of the present invention is the amount of thermoplastic polyethylene-based polymer in the layer facing the inside of the package, i.e., 40 g / m 2 or 35 g / m 2 and 25 g / m 2 However, polyethylene has a lower oxygen barrier property relative to impregnated and / or coated paper substrates, so this has no practical effect on the comparison of oxygen transmission rates through flat, unfolded materials. Typical oxygen transmission rates for 40 μm thick LDPE are 600-900 cm³ at 23°C. 3 / m 2 / 24 hours / 0.2 atmospheres. Furthermore, a thicker polyethylene layer would be expected to be beneficial in reducing OTR, but these results show no such effect. This positive effect comes from the gas barrier coated paper material, in this case the barrier coated paper substrate.

[0246] As shown in Table 2, the paper substrate of the present invention (Invention Example 1) not only provides the laminate material with the lowest measured OTR after forming the package, but also the laminate material with the lowest loss factor, indicating further improvement in robustness during formation of the package. If the flat material has a low OTR value, it will be of less value in oxygen-sensitive packaging if the OTR value increases after being folded and formed into a filled three-dimensional package.

[0247] Test 3: Recyclability

[0248] [Table 3]

[0249] # / LDPE 12g / m2 / Paperboard 80mN / LDPE 20g / m2 / Aluminum foil 6.3μm / Adhesive EAA copolymer 6g / m2 + 19g / m2 Blend LDPE + mLLDPE / ## / LDPE 12g / m2 / Paperboard 80mN / LDPE 20g / m2 / Paper base + PVOH + Metal vapor deposition / Adhesive EAA copolymer 6g / m2 + 19g / m2 Blend LDPE + mLLDPE / LDPE + mLLDPE /

[0250] Coarse waste, i.e., the non-fibrous recyclable portion of the laminate material (polymer, aluminum foil, and some of the non-peelable fibers), was measured after repulping in a Valmet pulper. Repulping was performed in the same manner as for the determination of CSF values ​​from the repulping of only paper substrates (Table 1) above, except that the laminate packaging material to be repulped and analyzed was first cut into pieces 30 x 90 mm in size. Coarse waste was sieved through a 10 mm diameter perforated plate, dried to 0% moisture content, and calculated as the weight percent of the dry (0% moisture content) material introduced into the pulper.

[0251] Coarse waste, determined by a contractor contracted to a global industrial supplier of textile processing and recycling equipment, was produced in a similar manner, except that 20 g of laminate material was mixed with 2 liters of water and allowed to disintegrate for 18 minutes to a consistency of approximately 1% instead of 3.3%. The water temperature for this repulping test was also kept at 57°C.

[0252] From the above, it has been confirmed that the previously explored paper substrates for oxygen barrier coatings in the prior art can produce relatively high oxygen barrier levels in laminated packaging materials and packages filled and sealed therefrom, but do not lead to a reduction in the amount of waste material in existing recycling processes, such as the recycling of used beverage cartons. Although aluminum foil as a raw material may be avoided, the amount of material (coarse waste) discarded or incinerated from the recycling of materials will be similarly high, as seen in Comparative Examples 6 and 5, as tested by the recycling company mentioned above.

[0253] Although a comparative evaluation of prior art paper-based barrier laminates using the Valmet pulper and the repulping method described above has not been performed, the results of Comparative Example 6 and Comparative Example 5 suggest that the Valmet process would also generate a high percentage of coarse waste, similar to the reference aluminum foil material tested. On the other hand, the laminate materials of Comparative Example 1 and Comparative Example 3 exhibit significantly lower waste rates, e.g., less than 20 wt% coarse waste. As shown in Table 3, the laminate material containing the paper substrate of Comparative Example 1 appears to require a slightly longer repulping time compared to the laminate material of Comparative Example 3, but in any case, it decomposes similarly and produces a similarly low percentage of coarse waste after a longer repulping time, such as 50 minutes in this case. The laminate material tested for repulping in Comparative Example 3 contains a paper substrate with a similar composition to that of Comparative Example 2 but with a higher basis weight. The laminate packaging material of Comparative Example 2 is expected to generate a similarly low amount of coarse waste.

[0254] Also, as shown in Table 2, the laminate material comprising the barrier-coated high-density stretchable paper substrate of Example 1 of the present invention is expected to have repulpability at least equivalent to that of Comparative Example 1 of Table 3, i.e., the high-density paper substrate of Example 1 of the present invention has significantly improved recycling and repulpability properties compared to the prior art reference materials (Comparative Examples 5 and 6 (and Comparative Examples 4-1 and 4-2)) because they have very similar fiber content, composition and construction, and the structure of the laminate material is the same.

[0255] conclusion Pre-filled 200 ml packages made from standard laminates of coated paper of Comparative Examples 1 and 2 in our concurrently pending, not yet published patent applications, exhibited a drop of approximately 0.03 cm at 23°C and 50% RH. 3The OTR test showed a generally very low oxygen transmission rate of 0.03 / m² / day / 0.2 atmospheres. Furthermore, this value did not deteriorate significantly in an environment of 23°C and 80% RH. The OTR test was conducted 2-3 weeks after the manufacture of the filled and sealed packages. The oxygen transmission rate of the 200ml package was 0.03, which is approximately 2-3 times longer shelf life for oxygen-sensitive products than the oxygen transmission rate of Comparative Example 4-2 (i.e., the prior art document) of approximately 0.075.

[0256] The oxygen transmission rate in 200 ml packages made from the laminate material according to Inventive Example 1 is further improved to be less than 0.02, providing a shelf life that is more than four times better than that obtained from Comparative Example 4-2 (i.e., the prior art). The OTR (measured on the flat laminate material) of the laminate materials of Comparative Examples 1 and 2 and Inventive Example 1 is at least as good as similar paper-based barrier laminates of the prior art.

[0257] But most importantly, the recently developed materials of the present invention do not suffer the same degree of loss of oxygen barrier properties as the laminate material is converted into a filled, formed, and heat-sealed package. However, this effect is not attributable to the higher amount of PVOH coated. While the difference in PVOH coating weight may improve the oxygen barrier properties of the flat laminate (unfolded) material, it cannot explain the improvement in oxygen barrier properties in the filled and sealed package beyond a minor level.

[0258] In general, package integrity is demonstrated to be good with the paper-based barriers of Comparative Examples 1 and 2 and Inventive Example 1. Furthermore, the paper substrate basis weight is between 30 and 65 g / m 2 , for example 35 to 60 g / m 2 , for example, 35 to 55 g / m 2 , for example 35 to 50 g / m 2It has been found that a lower fiber content improves package integrity. Therefore, the thickness of the paper substrate should preferably be 30-60 μm, e.g., 30-55 μm, e.g., 30-50 μm, e.g., 30-45 μm. A thicker coated, non-stretchable paper substrate requires more polymer in the thermoplastic heat-sealable layer to create a tight, durable seal when the laminate material is transformed into a filled, sealed, cubic-shaped package. A thinner paper substrate can reduce the proportion of thermoplastic polymer needed in the overall packaging laminate. This is crucial because packaging materials will need to be compatible with future recycling streams with very high fiber content, allowing materials to be recycled and reused rather than becoming waste.

[0259] Stretchable paper substrates also exhibit this effect, and it is expected that even better results will be obtained by using thinner, stretchable paper substrates, such that the content of thermoplastic heat-sealable polymer in the laminate packaging material can be further reduced.

[0260] Furthermore, the impregnated high-density paper substrates of Comparative Examples 1 and 2 provided laminated materials with improved recycling and repulping properties compared to both aluminum foil-based and non-aluminum foil gas barrier-based laminated packaging materials. The recycling and repulping properties of high-density stretchable papers such as those in Inventive Example 1 are expected to be similarly good because the paper itself has a very similar composition and cellulose content. Making the paper substrate more extensible, i.e., stretchable, i.e., with a high breaking strain in the machine direction (MD), for example, using an Expander extension unit, is not expected to change the repulping properties. This improvement also fully supports the development of more sustainable packaging materials. This improvement also enables a higher fiber-based content in laminated packaging materials for packaging highly oxygen-sensitive products, such as fruit juices and fruit- and vegetable-based foods containing natural vitamin C.

[0261] With reference to the accompanying drawings: FIG. 1a shows a cross-sectional view of one embodiment of a paper substrate 10a of the present invention. The paper substrate 10a is made from moderately refined kraft cellulose fibers to obtain good recycling properties of the paper. To obtain good recycling properties of the paper, moderately refined polyvinyl alcohol fibers are used. Furthermore, the paper has a machine direction stretch of at least 3%. This is impregnated with polyvinyl alcohol having a high degree of hydrolysis in a film press operation during the papermaking process (11a). The dry weight of the PVOH impregnated from the top surface is about 1 to 1.5 g / m. 2 The paper substrate is impregnated from both the top and back sides, with a total of about 2-4 g / m 2 The PVOH and / or starch may be impregnated on the upper surface, for example, a combination of PVOH from the top surface and starch from the back surface.

[0262] FIG. 1b shows in cross-section an embodiment of a high density stretchable paper substrate 10b of the present invention obtained by supercalendering the impregnated paper substrate 10a of FIG. 1a at high pressure and temperature to obtain a thinner and denser stretchable paper substrate.

[0263] FIG. 1c shows an SEM image of a surface portion of a preferred paper substrate of the present invention, which has been formed, wet-pressed, dried, compressed, further dried, impregnated with PVOH, and supercalendered, and then processed to a density of about 3 g / m. 2 It also has a continuous gas barrier coating of PVOH.

[0264] Figure 1d shows an SEM image of the surface of a paper substrate that was impregnated with PVOH and supercalendered, but not coated with a gas barrier coating. As shown in Figure 1d, the impregnated PVOH does not form a film or continuous coating on the surface. The impregnated PVOH has penetrated the fiber web. The impregnated paper substrate used in Comparative Example 1 also exhibited a similar surface, and no PVOH film or continuous coating was observed on the surface of the paper.

[0265] Figure 1e is an SEM image of a cross section 10e of the non-stretchable high-density paper substrate used in Comparative Example 1. The dark gray areas 15 are PVOH, and the light gray areas 16 are fibers. Unfilled pores 17 are also present. As a result, the high-density comparative paper is not saturated with PVOH. However, Figure 1e shows the presence of PVOH within the fiber web, and the surface image of the paper reveals that the majority of the PVOH is present within the bulk fiber of the paper. Only a small amount of PVOH is present on the surface of the paper. Considering Figures 1c and 1d above, this is likely to be the case for a similar, but compressed, stretchable paper made from similar cellulose fibers in a similar manner. As shown above, the gas barrier properties of the folded and molded packaging container are further improved by the gas barrier-coated compressed paper of the present invention, which is otherwise manufactured in a very similar manner, compared to Comparative Example 1.

[0266] Figure 2a shows in cross section an embodiment of a stretchable paper substrate 20a similar to that shown in Figure 1a. The same compressed paper web produced for Figures 1a and 1b is dewatered, wet pressed, and dried to form the stretchable paper substrate without further polymer impregnation in a size press process.

[0267] FIG. 2b shows in cross section an embodiment of a high density stretch paper substrate 20b obtained by further supercalendering the stretch paper substrate 20a of FIG. 2a at high pressure and temperature to obtain a thinner, higher density stretch paper substrate.

[0268] Figure 3a shows in cross section an embodiment of a gas barrier coated stretchable paper substrate 30a of the present invention. Stretchable paper substrates 31a; 31b (layer thickness ratios in Figures 1-5 do not reflect actual thicknesses or relative thickness ratios) taken from Figure 1a, or preferably from Figure 1b, are coated with a water gas barrier composition comprising PVOH in two coating steps with intermediate and subsequent drying steps, to a total dry weight of 1.5 g / m. 2 twice that, or 3 g / m 2A layer 33a of the above is applied.

[0269] Thus, the PVOH-coated stretchable paper substrate 30a (i.e., including 31a and 33a) further has a vapor-deposited coating of aluminum vapor deposition 34a on the PVOH coating 33a. This barrier coating configuration in combination with the stretchable paper substrate provides a gas barrier laminate portion, allowing non-foil laminate packaging materials (i.e., laminate packaging materials that do not contain conventional micrometer-thick (5-10 μm) aluminum foil or other metal foils) to provide high and durable gas barrier properties in folded, filled, and heat-sealed packaging containers made from such non-foil packaging materials.

[0270] Figure 3b shows a further embodiment of a gas-barrier-coated stretchable paper substrate 30b of the present invention, in which the stretchable paper substrate 20a or 20b from Figure 2a or 2b may be used. Instead of having a polymer impregnated into the fibrous interior of the paper substrate, the paper substrate is pre-coated with a base coating 32b containing a polymer composition that imparts greater smoothness and / or surface quality to the multilayer paper substrate barrier structure. A gas-barrier coating 33b of PVOH followed by a metal vapor deposition coating 34b are applied over the base coating 32b in the same manner and in the same amounts as in Figure 3a. The base coating forms a "bridge" to the stretchable paper substrate. Improved properties are obtained similar to those of the impregnated gas-barrier-coated paper substrate 30a.

[0271] Figure 3c shows a further embodiment of a gas-barrier-coated stretchable paper substrate 30c of the present invention, corresponding to the PVOH-coated paper substrate of Figures 3a or 3b, prior to final vapor deposition coating with a metallized vapor-deposited coating (base or pre-coating 32c is optional). This is another variation of a paper-based gas barrier material that may be combined and laminated with additional complementary barrier materials in a laminate packaging material, such as a polymer film with a vapor-deposited barrier coating thereon. Such a laminate packaging material also provides better and more durable non-foil gas barrier properties in folded, filled, and heat-sealed packaging containers, thanks to the high machine-direction stretchability of the paper substrate 31c.

[0272] In FIG. 4a, a laminate packaging material 40a 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 41 of paperboard having a basis weight of 1000g, and an outer liquid-tight, heat-sealable layer 42 of polyolefin applied to the outside of the bulk layer 41, which layer faces the outside of the packaging container produced from the packaging laminate. This layer 42 is transparent to allow a printed decorative pattern 47 applied to the bulk layer of paper or paperboard to be visible on the outside, thereby informing consumers of the package contents, package brand, and other information targeted at consumers in retail establishments and food stores. The polyolefin of the outer layer 42 is conventional low-density polyethylene (LDPE) of heat-sealable quality, but can also include more similar polymers, including LLDPE. The coating weight is approximately 12 g / m. 2The innermost liquid-tight heat-sealable layer 43 is positioned opposite the bulk layer 41, and this layer faces the inside of the packaging container made from the packaging laminate. The innermost heat-sealable layer 43, which will form a strong lateral heat seal of the liquid packaging container made from the laminate packaging material, comprises one or more combinations of polyethylenes selected from the group consisting of LDPE, linear low-density polyethylene (LLDPE), and LLDPE made by polymerizing ethylene monomers and C4-C8, more preferably C6-C8, α-olefin alkylene monomers in the presence of a metallocene catalyst, so-called metallocene-LLDPE (m-LLDPE). This has a density of about 19 g / m 2 is applied in an amount of

[0273] The bulk layer 41 is laminated to the uncoated side, i.e., 45a, of the barrier-coated paper substrate 30a from Figure 3a, by an intermediate bonding layer 46 of low-density polyethylene (LDPE). The intermediate bonding layer 46 is formed by melt extruding a thin polymer molten curtain between the two paper webs, so that the bulk layer and the barrier-coated paper substrate are laminated together when all three layers pass through a cooled press roller nip. The thickness of the intermediate bonding layer 46 is 12-22 μm, e.g., 12-18 μm.

[0274] The innermost heat sealable layer 43 may consist of one layer, or alternatively may consist of two or more partial layers of the same or different types of LDPE or LLDPE or blends thereof, and is well adhered to the metallized barrier coated surface 34a of the barrier coated paper substrate 45a, i.e., 30a, by an intermediate coextruded tie or adhesive polymer layer 48, for example, of ethylene acrylic acid copolymer (EAA), thereby achieving a coating density of 5-7 g / m 2 The innermost layer 43 is bonded to the barrier coated paper substrate 30a by applying the tie layer 48 and the innermost layer 43 together in a single melt co-extrusion coating process.

[0275] Alternatively, the bulk layer 41 may be laminated to the barrier-coated paper substrate depicted in Figure 3a by wet lamination using an intermediate tie layer 46b, e.g., a thin layer of adhesive polymer, obtained by applying an aqueous dispersion of PVOH, starch, or polyvinyl acetate adhesive to one of the surfaces to be bonded together and then pressing them together in a roller nip. Thanks to the relatively thick absorbent bulk layer of cellulosic structure, this lamination process may be carried out in an efficient low- or ambient-temperature lamination process at industrial speeds, without the energy-consuming drying operations normally required to promote water evaporation. The dry coating weight of the intermediate tie layer 46b may be several g / m². 2 Approximately, for example, 2 to 6 g / m 2 No drying or evaporation is required.

[0276] Therefore, the amount of thermoplastic polymer in this laminate layer can be significantly reduced compared to conventional polyethylene 46 melt extruded laminate adhesive layers.

[0277] In Figure 4b, in an alternative embodiment, instead of the gas barrier coated paper substrate 30a, the gas barrier coated paper substrate 30b shown in Figure 3b is laminated to the same laminate structure as in Figure 4a as gas barrier coated structure 45b.

[0278] FIG. 5 shows a further embodiment of a laminate packaging material 50 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 and a liquid-tight, heat-sealable outer layer 52 of polyolefin applied to the outside of the bulk layer 51, this layer facing the outside of a package made from the packaging laminate. The polyolefin of the outer layer 52 is a conventional low-density polyethylene (LDPE) of heat-sealable quality, having a basis weight of 12 g / m 2 Although the coating is applied in an amount of 1000 ppm, it may contain additional similar polymers, including LLDPE.

[0279] The innermost liquid-tight heat-sealable layer 53 is positioned opposite the bulk layer 51 and faces the inside of a packaging container made from the packaging laminate, i.e., layer 53 is in direct contact with the packaged product. This innermost heat-sealable layer 53, which will form a strong heat seal in a liquid packaging container made from the laminate packaging material, comprises one or more combinations of polyethylenes selected from the group consisting of LDPE, linear low-density polyethylene (LLDPE), and LLDPE made by polymerizing ethylene monomers and C4-C8, more preferably C6-C8, α-olefin alkylene monomers in the presence of a metallocene catalyst, so-called metallocene LLDPE (m-LLDPE).

[0280] The barrier-coated paper substrate 30c of Figure 3c is further laminated by melt extrusion lamination of a polymeric film substrate 54a, which is a film of biaxially oriented polypropylene (BOPP), to a complementary barrier film 54 comprising a metallized polymeric film substrate 54a coated with an aluminum-vaporized barrier coating 54b, with an intermediate tie layer 59 of low-density polyethylene (LDPE). With such a laminate material, moisture-sensitive gas barrier coatings, such as PVOH coatings, can be protected by the additional metallized coating of the metallized polymeric film located on the inner side of the laminate material, i.e., the side closest to the liquid or wet food content.

[0281] The bulk layer 51 is laminated to the uncoated, unlaminated side of the barrier-coated paper substrate 30c of Figure 3c by wet lamination with an intermediate adhesive layer 56 of a thin layer of adhesive polymer obtained by applying an aqueous dispersion of PVOH or polyvinyl acetate adhesive to one of the surfaces to be bonded together and then pressing them together with a roller nip. This lamination step is carried out at a density of a few g / m², as depicted in Figure 4b. 2 It may be performed with efficient cold lamination or ambient lamination using only a moderate intermediate adhesive layer 56, eliminating the need for drying and evaporation.

[0282] Therefore, this laminate packaging material also allows for a reduction in the amount of thermoplastic polymer in the laminate layer compared to a conventional polyethylene melt-extruded laminate adhesive layer as described in FIG. 4a.

[0283] An innermost layer 53 is applied onto the barrier coated film 54, optionally with an adjacent adhesive polymer layer 58, in a coextrusion coating operation.

[0284] According to a further embodiment not shown, the uncoated paper substrate 10a or 10b of Figure 1a or 1b, or the paper substrate 20a or 20b of Figure 2a or 2b, may be laminated to the same laminate structure described above as the barrier structure 45, instead of the gas barrier coated paper substrate 30c.

[0285] The increased machine direction breaking strain of the paper substrate provides flexibility to the laminate packaging material, supporting and cushioning the various gas barrier coatings and layers within the laminate material as it is folded and formed into a cubic packaging container for liquid carton packaging.

[0286] FIG. 6a shows an aqueous dispersion coating process 60a, which may be used to apply a gas barrier coating 12 from a water gas barrier composition onto a substrate or to apply an aqueous adhesive composition for wet laminating two webs, at least one of which has a fibrous cellulosic surface. A paper substrate web 61a (e.g., paper substrates 11a and 11b in FIG. 1 or paper substrates 21a and 21b in FIG. 2) is fed to a dispersion coating station 62a, where an aqueous dispersion composition is applied to the upper surface of the substrate by a roller. The aqueous composition has a moisture content of 80-99% by weight, and much of the water present on the wet-coated substrate is dried by heat to evaporate off and form a continuous coating with homogeneous and uniform quality in terms of barrier and surface properties, i.e., uniformity and wetting. Drying is performed by a hot air dryer 63a, which also evaporates off moisture from the surface of the paper substrate. The temperature of the substrate is maintained constant at 60-80°C as it passes through the dryer. Alternatively, drying may be partially assisted by radiant heat from infrared IR lamps in combination with hot air convection drying.

[0287] The resulting barrier coated paper substrate web 64a is cooled and wound onto a reel for intermediate storage, after which the paper substrate 64a is further vapor coated with a barrier vapor coating.

[0288] FIG. 6b shows the process (60b) of the final lamination step in the manufacture of laminated packaging materials such as 40a, 40b or 50 in FIGS. 4 and 5, respectively, after the bulk layer 41, 51 has first been laminated to the barrier-coated paper substrate from FIG. 3.

[0289] Bulk layer paperboard may be laminated to a barrier coated paper substrate by wet cold dispersion adhesive lamination or melt extrusion lamination.

[0290] The resulting paper prelaminate web 61b is transported from an intermediate storage reel or directly from a lamination station for laminating the paper prelaminate. The non-laminated, i.e., printed, side of the bulk layer 41; 51 is bonded in a cooled roller nip 63 to a molten polymer curtain 62 of LDPE, which forms the outermost layer 42; 52 of the laminate material. The LDPE is then extruded through an extruder feedblock and die 62b. The paper prelaminate web, with the outermost layer 62; 42; 52 coated on the printed side, i.e., the outside, then passes through a second extruder feedblock and die 64b and lamination nip 65, where a molten polymer curtain 64 is bonded to and coated on the other side of the prelaminate, i.e., the barrier-coated side of the paper substrate. In this way, the innermost heat-sealable layer 64;43;53 is coextrusion coated onto the inside of the paper pre-laminate web, ultimately forming a laminated packaging material 66, which is wound onto a storage reel (not shown).

[0291] These two co-extrusion steps in laminating roller nips 63 and 65 may alternatively be performed as two successive steps in reverse order.

[0292] According to another embodiment, one or both of the outermost layers may 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 a barrier-coated paper substrate, and then the two pre-laminated paper webs may be bonded together as described above.

[0293] FIG. 7a is a perspective view of an example of a plant 70 for physical vapor deposition (PVD) of, for example, aluminum metal vapor coatings onto a web substrate of the present invention. A coated or uncoated paper substrate 71 is subjected on its precoated side to continuous vapor deposition of evaporated aluminum 72 to form a vapor-deposited layer of aluminum, or alternatively, to a mixture of oxygen and aluminum vapor to form a vapor-deposited coating of aluminum oxide. The coating is provided to a thickness of 5-200 nm, e.g., 5-100 nm, e.g., 10-50 nm, to form a barrier-coated paper substrate 73 of the present invention. The aluminum vapor is formed by ion bombardment of a solid aluminum piece evaporation source 72. In the case of aluminum oxide coatings, some oxygen gas may also be injected into the plasma chamber through an inlet port.

[0294] Figure 7b shows a perspective view of an example of a plant 70b for plasma-enhanced chemical vapor deposition (PECVD) coating, such as hydrogenated amorphous diamond-like carbon coatings, on a web substrate of the present invention. A web substrate 74a is subjected on one surface to continuous PECVD of plasma in a plasma reaction zone 75 formed in the space between a magnetron electrode 76 and a cooled web transport drum 77, which also functions as an electrode. The film is advanced through the plasma reaction zone along the periphery of the drum by the rotating drum. The plasma for vapor deposition coating of the amorphous DLC coating layer may be generated by injecting a gas precursor composition, including, 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 primary PECVD method, such as silicon oxide coatings (SiOx) starting from organosilicon compound precursor gases. The PECVD plasma chamber is maintained under vacuum by continuously evacuating the chamber through outlet ports 78a and 78b.

[0295] FIG. 8a shows an embodiment of a packaging container 50a made from a packaging laminate according to the present invention. This packaging container is particularly suitable for beverages, sauces, soups, and the like. Typically, such a packaging container has a volume of approximately 100 to 1000 ml. It can be any shape, but is preferably brick-shaped, with longitudinal seals 81a and lateral seals 82a, and optionally an opening device 83. In another embodiment, not shown, the packaging container can be wedge-shaped. To achieve this "wedge" shape, only the bottom of the package is folded, with the bottom lateral heat seal hidden beneath triangular corner flaps that are folded and sealed to the bottom of the package. The top lateral seal remains unfolded. In this way, the partially folded packaging container is easy to handle and dimensionally stable enough to be placed on a grocery store shelf or flat surface.

[0296] Figure 8b shows an alternative packaging container 80b made from an alternative packaging laminate according to the present invention. This alternative packaging laminate is thinner by having a thinner paper bulk layer and therefore does not have sufficient dimensional stability to form a parallelepiped or wedge-shaped package, and no folds are formed after transverse seal 82b. The package remains a pillow-like bag-like container and is distributed and sold in this form.

[0297] 8c shows a gable-top package 50c that is folded and formed from a pre-cut sheet or blank of a laminated packaging material including 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.

[0298] 8d shows a bottle-shaped package 50d that combines a sleeve 54 formed from a pre-cut blank of the laminate packaging material of the present invention with a top 55 formed from injection-molded plastic in combination with an opening device such as a screw cork. This type of package is sold, for example, under the trade names Tetra Top® and Tetra Evero®. These specialized packages are formed by attaching a molded top 55 with an opening device in a closed state to a tubular sleeve 54 of laminate packaging material, sterilizing the resulting bottle-top capsule, filling it with a food product, and finally folding and sealing the bottom of the package.

[0299] Figure 9 illustrates the principle described in the introduction to this application. A web of packaging material is formed into a tube 91 by overlapping longitudinal edges 92a, 92b of the web and heat-sealing them together, thereby forming an overlap joint 93. The tube is continuously filled (94) with the liquid food product to be filled and divided into individual filled packages by repeating double transverse seals 95 of the tube at predetermined intervals below the level of the filled contents in the tube. Packages 96 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 pre-defined crease lines in the material.

[0300] 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 claims.

Claims

1. 1. Use of a paper substrate (10a; 10b; 20a; 20b) for gas barrier material in a laminate packaging material for packaging liquid, semi-liquid or viscous food or oxygen-sensitive food such as water, comprising: The paper substrate has a basis weight of 30 to 100 g / m2 measured according to ISO 536:2012. ２ and having a machine direction strain at break of greater than 3% as measured in accordance with ISO 1924-3:2005 and a Bendtsen surface roughness of at least one surface of less than 150 ml / min as measured in accordance with ISO 8791-2:2013. Use of a paper substrate (10a; 10b; 20a; 20b).

2. the paper substrate has a machine direction strain at break measured according to ISO 1924-3:2005 in the range of 3.5% to 9.0%, for example 4.0% to 8.0%; 2. The use according to claim 1.

3. the paper substrate has a cross-direction strain at break of greater than 5.0% measured according to ISO 1924-3:2005; 3. Use according to claim 1 or 2.

4. The paper substrate has a density of 90 g / m2 measured according to ISO 536:2012 ２ For example, 80 g / m ２ Below, for example, 70 g / m ２ Below, for example, 66 g / m ２ Below, for example, 60 g / m ２ For example, 55 g / m ２ Below, for example, 50 g / m ２ having a basis weight of: Use according to any one of claims 1 to 3.

5. The bendzen surface roughness of at least one side is 100 ml / min or less, for example, 70 ml / min or less; Use according to any one of claims 1 to 4.

6. the paper substrate is impregnated with a polymer selected from the group consisting of polyvinyl alcohol, PVOH, ethylene vinyl alcohol, EVOH, starch, starch derivatives, carboxymethyl cellulose, CMC, or other cellulose ethers; Use according to any one of claims 1 to 5.

7. the paper substrate having a base coating comprising a polymer applied to an upper surface of the paper substrate; Use according to any one of claims 1 to 6.

8. The paper substrate has a strength of at least 800 kg / m as measured according to ISO 534:2011 ３ , e.g. at least 900 kg / m ３ , e.g. at least 1000 kg / m ３ having a density of Use according to any one of claims 1 to 7.

9. The paper base material is calendered, such as by supercalendering. Use according to any one of claims 1 to 8.

10. the cellulose fibers comprising at least 90% of the dry weight of the paper; Use according to any one of claims 1 to 9.

11. The paper substrate is kraft paper. Use according to any one of claims 1 to 10.

12. 1. A gas barrier coated paper substrate (30a; 30b; 30c) for use as a gas barrier material in a laminated packaging material for oxygen sensitive foods, such as liquid, semi-liquid or viscous foods or water, comprising:

12. A gas barrier coated paper substrate according to the use of any one of claims 1 to 11, wherein said paper substrate has at least one gas barrier coating (33a, 34a; 33b, 34b; 33c) of at least one gas barrier material to a total coating thickness of 2 to 5000 nm, for example 2 to 4000 nm.

13. said at least one gas barrier coating (33a; 33b; 33c) being formed by coating and subsequent drying of a dispersion or solution of an aqueous composition of said at least one gas barrier material; The gas barrier coated paper substrate according to claim 12.

14. the at least one gas barrier material comprises a polymer selected from the group consisting of polyvinyl alcohol, PVOH, 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; The gas barrier coated paper substrate of claim 12 or 13.

15. the paper substrate having a vapor-deposited coating (34a; 34b) of a gas barrier material selected from metals, metal oxides, inorganic oxides, and amorphous diamond-like carbon coatings; The gas barrier coated paper substrate according to any one of claims 12 to 14.

16. The paper substrate has a first gas barrier coating (33a; 33b) formed by coating a dispersion or solution of an aqueous composition of the gas barrier material and then drying it, and further has a vapor-deposited coating (34a; 34b) of a gas barrier material selected from metals, metal oxides, inorganic oxides, and amorphous diamond-like carbon applied on the first gas barrier coating. The gas barrier coated paper substrate according to any one of claims 12 to 15.

17. A laminate packaging material (40a; 40b; 50) for packaging oxygen-sensitive foods, such as liquid, semi-liquid or viscous foods or water, comprising the use of the paper substrate (10a; 10b; 20a; 20b) according to any one of claims 1 to 11 or the gas barrier coated paper substrate (30a; 30b; 30c) according to any one of claims 12 to 16, The laminate packaging material has a first outermost layer (42; 52) of a liquid-tight material, a second innermost layer (43; 53) of a liquid-tight material, and a bulk layer (41; 51) of paper or paperboard or other cellulosic material, and the paper substrate (10a; 10b; 20a; 20b) or the gas barrier coated paper substrate (30a; 30b; 30c) is laminated between the bulk layer and the second innermost layer. Laminated packaging materials.

18. The paper substrate, or the gas barrier coated paper substrate, is coated with an aqueous inter-adjacent adhesive composition (46b; 56) at a rate of 5 to 10 g / m, comprising a water-dispersible binder selected from the group consisting of acrylic polymers and copolymers, starch, starch derivatives, cellulose derivatives, polymers and copolymers of vinyl acetate, copolymers of vinyl alcohol, and copolymers of styrene-acrylic latex or styrene-butadiene latex. ２ , for example, 1 to 5 g / m ２ laminated to the bulk layer by coating and drying; 18. The laminate packaging material of claim 17.

19. A pre-fabricated polymer film is laminated on the inside of the paper substrate or the gas barrier coated paper substrate to improve the robustness of the mechanical properties of the laminate packaging material.

19. The laminate packaging material according to claim 17 or 18.

20. a pre-manufactured polymer film (54, 54a) laminated to the inside of the paper substrate (10a; 10b; 20a; 20b) or the gas barrier coated paper substrate (30c), i.e., on the side of the paper substrate opposite to the side laminated to the bulk layer; The pre-fabricated polymer film (54, 54a) has a vapor-deposited coating (54b) of a gas barrier material selected from metals, metal oxides, inorganic oxides, and amorphous diamond-like carbon coatings. A laminate packaging material (50) according to any one of claims 17 to 19.

21. A packaging container (50a; 50b; 50c; 50d) for packaging oxygen-sensitive foods such as liquid, semi-liquid or viscous foods or water, comprising a laminate packaging material (40a; 40b; 50) according to any one of claims 17 to 20.

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