Use of paper substrate, barrier-coated paper substrate, laminated packaging material comprising such substrate, and packaging container

Abstract

The present invention relates to the use of a paper substrate (10a, 10b) made of cellulosic fibres as a gas barrier material in a laminated packaging material (40a) for packaging oxygen-sensitive products, and also to such a coated paper substrate (30a) for improving gas barrier properties. The invention also relates to a laminated packaging material (40a) comprising a paper substrate or a barrier-coated paper substrate and a packaging container comprising the laminated packaging material for packaging oxygen-sensitive products, such as food products.

Description

Technical Field

[0001] The present invention relates to the use of a paper substrate made of cellulose fibers as a gas barrier material in a laminated packaging material for packaging oxygen-sensitive products, such as oxygen-sensitive foods and liquid, semi-liquid or viscous foods or water, and further coating such a high-density paper substrate to improve the gas barrier properties when subjected to mechanical stress. The present invention also relates to a laminated packaging material comprising a coated or uncoated paper substrate, and a packaging container for packaging oxygen-sensitive products comprising the laminated packaging material. Background of the Invention

[0002] Single-use carbon-type packaging containers for liquid foods are usually made of paperboard or carton-based packaging laminates. One such common packaging container is sold under the trademark Tetra Aseptic packaging containers are marketed and are mainly used for aseptic packaging of liquid foods (e.g. milk, juice, etc.) for long-term storage at room temperature. The packaging material in such known packaging containers is usually a laminate material, which includes a main layer or core layer of paper, paperboard or other cellulose-based material, and a liquid-tight outer layer of thermoplastic. In order to make the packaging container airtight, in particular oxygen-tight, for example for the purpose of aseptic packaging and milk or juice packaging, the laminate material in these packaging containers usually includes at least one additional layer, most commonly aluminum foil.

[0003] On the inside of the laminate, i.e. the side intended to face the filled food content of the container produced from the laminate, there is an innermost layer applied to the aluminum foil, which innermost layer may consist of one or several partial layers comprising a heat-sealable thermoplastic polymer, such as an adhesive polymer and / or a polyolefin. Likewise on the outside of the bulk layer, there is an outermost heat-sealable polymer layer.

[0004] The packaging containers are usually produced by means of modern high-speed packaging machines of the type which form, fill and seal packages from a web or preformed blank of packaging material. Thus, the packaging container can be produced by reforming a web of laminated packaging material into a tube, by welding together the inner and outermost heat-sealable thermoplastic polymer layers, so that the two longitudinal edges of the web are joined to each other in a lap joint. The tube is filled with the intended liquid food product and subsequently divided into individual packages by repeatedly sealing the tube transversely at a predetermined distance from each other below the level of the contents in the tube. The packages are separated from the tube by cuts along the transverse seals and by forming folds along prepared crease lines in the packaging material to form the desired geometric configuration, usually a parallelepiped.

[0005] The main advantage of this continuous tube form, fill and seal packaging process concept is that the web can be sterilized continuously before tube forming, thus providing the possibility of an aseptic packaging process, i.e., one in which both the liquid contents to be filled as well as the packaging material itself are bacteria-reduced and the filled packaging containers are produced under clean conditions, so that the filled packages can be stored for long periods of time even at ambient temperature without the risk of microbial growth in the filled product. As mentioned above, Tetra Another important advantage of the type packaging method is the possibility of continuous high-speed packaging, which has a considerable impact on cost efficiency.

[0006] Packaging containers for sensitive liquid foods, such as milk or juice, can also be produced from sheet blanks or preformed blanks of the laminated packaging material of the present invention. The packaging is produced from a tubular blank of a folded flat packaging laminate, which is first constructed into an open tubular container capsule, one open end of which is closed by folding and heat sealing of an integral end plate. The thus closed container capsule is filled with the food in question, such as juice, which flows out through its open end and is then closed by further folding and heat sealing of the corresponding integral end plate. An example of a packaging container produced from sheet and tubular blanks is the traditional so-called gable top package. There are also packages of this type with a molded top and / or a screw cap made of plastic.

[0007] The aluminum foil layer in the packaging laminate provides gas barrier properties that are substantially superior to most other gas barrier materials. With current performance levels on the market, traditional aluminum foil packaging laminates for aseptic packaging of liquid foods remain the most cost-effective and low carbon emission packaging material. However, efforts are underway to replace aluminum foil with non-foil barrier materials to further reduce the carbon footprint.

[0008] Any other material competing with foil-based materials must be cost-effective in terms of raw materials, have comparable food preservation properties, a reduced carbon footprint, and have relatively low complexity in converting the material into a finished packaging laminate.

[0009] In the efforts to develop non-aluminum foil materials for liquid food carton packaging, it is also generally encouraged to develop prefabricated films or sheets with high and multiple barrier functions, which can replace aluminum foil barrier materials in traditional laminated packaging materials, or combine several separate barrier layers in laminated materials and adapt them to traditional lamination and manufacturing processes.

[0010] A preferred type of such an alternative, more environmentally sustainable barrier material is a barrier coated paper substrate made by aqueous dispersion coating or vapor deposition coating onto a thin paper carrier substrate. There are various aqueous dispersion coating processes and vapor deposition coating processes and material formulations for such coatings, and there is a need for a cost effective "non-foil" type (i.e. non-aluminum foil) barrier material with improved performance properties in packaging laminates for liquid food packaging, with respect to barrier properties, particularly to gases (e.g. oxygen).

[0011] An earlier patent publication WO 2011 / 003565 A1 discloses a non-aluminium foil packaging material comprising a dispersion coated and subsequently metallized paper or cellulose based substrate for the purpose of induction heat sealing.

[0012] Earlier patent publication WO2017 / 089508A1 discloses how to obtain improved barrier properties from metallized paper in similar packaging laminates in a similar manner (but by selecting a paper substrate that provides the best performance). This metallized paper substrate not only provides improved barrier properties, but also shows better stability of the metallized layer for induction heat sealing purposes.

[0013] However, there is still a need to further improve the oxygen barrier properties of prior art gas barrier coated paper substrates, particularly in the field of liquid and wet food packaging. There is also an increasing need to improve the performance of materials for gas barrier coated paper substrates and laminated packaging materials comprising them in terms of recyclability and environmental sustainability. Summary of the invention

[0014] It is therefore an object to utilize an improved paper substrate which contributes to good gas barrier properties of a laminated packaging material comprising the paper substrate and not an aluminum foil ("non-foil"), the purpose of which is to package oxygen-sensitive products.

[0015] It is also a general object to provide improved barrier coated paper substrates that provide or contribute to good gas barrier properties as well as improved recyclability and environmental sustainability of such non-foil laminated packaging materials.

[0016] Another object is to provide a foil-free laminated packaging material for oxygen sensitive products such as liquid, semi-liquid or viscous foods including water, which contains no aluminum foil but provides product barrier properties and gas barrier properties in a package made therefrom.

[0017] A specific object is to provide a cost-effective, non-foil, paper or paperboard based laminated packaging material relative to aluminium foil barrier materials, having good gas and water vapour barrier properties, as well as good recyclability and environmental sustainability, for the manufacture of packaging for long-term aseptic storage of liquid foods.

[0018] Another object of the present invention is to provide a cost effective, non-foil, paper or paperboard based, mechanically strong and heat sealable packaging laminate having good gas and water vapor barrier properties and good interlayer adhesion for use in manufacturing aseptic packaging containers for long term storage of liquid foods under ambient conditions and maintaining nutritional quality.

[0019] According to the present invention, as defined in the appended claims, these objects can be achieved by using an improved paper substrate, by such a paper substrate coated with a barrier, by a laminated packaging material comprising the improved paper substrate or the barrier coated paper substrate, and by a packaging container made from the laminated packaging material. SUMMARY OF THE INVENTION

[0020] According to a first aspect of the present invention, there is provided a use of a paper substrate made of cellulose fibers as a gas barrier material in a laminated packaging material, the laminated packaging material being used for packaging oxygen-sensitive products, such as for packaging oxygen-sensitive foods, such as for packaging liquid, semi-liquid or viscous foods or water, wherein the grammage of the paper substrate is measured according to ISO536:2012 and is 30 to 100 g / m 2 , the strain at break in the machine direction is higher than 3% measured according to ISO 1924-3:2005, and the Bendtsen surface roughness on at least one side is lower than 150 ml / min measured according to ISO 8791-2:2013.

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

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

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

[0024] The increased stretchability (i.e. strain at break) in the MD appears to add significant flexibility to the gas barrier coated paper structure having such a paper substrate. The present invention demonstrates that a gas barrier coated paper substrate having a strain at break of more than 3% when laminated into a paperboard based packaging material significantly improves the final oxygen barrier properties of a formed packaging container formed from the laminate.

[0025] The paper substrate can be composed of at least 90% cellulose fibers per dry weight of the paper. The paper substrate can be made from chemical pulp, such as Kraft fibers.

[0026] The paper substrate can have a basis weight of less than 90 g / m² according to ISO 536:2012 measurement 2 , for example, less than 80 g / m² 2 , for example, less than 70 g / m² 2 , for example, less than 66 g / m² 2 , for example, less than 60 g / m² 2 , for example, less than 55 g / m² 2 , for example, less than 50 g / m² 2 . It has been found that by using a thinner paper substrate to carry the barrier coating, there are general advantages for the integrity and robustness of the filled and sealed liquid carton packaging. Thinner paper seems to reduce the strain and mechanical stress acting on the gas barrier coating when folding and forming the packaging, thus also improving the final gas barrier properties of the filled and ready packaging container.

[0027] In another embodiment, the Bentzen surface roughness on at least one side is less than 100 ml / min, for example, less than 70 ml / min, for example, less than 50 ml / min. 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 in order to be as flexible as possible when formed and folded into a packaging container. Thicker coatings may be more susceptible to folding strain, and their application is also more difficult and costly. Since vapor deposition coatings and liquid dispersion coatings for gas barriers are preferably thin, they also need to have a uniform and reliable quality so that they can provide gas barrier performance at each point of the gas barrier material coating in the laminated packaging material that constitutes the final packaging container.

[0028] The paper substrate can be impregnated with a polymer at least from its top side, and the polymer is 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 side of the paper substrate is the side with the smoothest surface and / or the side to be further coated with a gas barrier coating. Since the paper substrate is impregnated with a polymer having high environmental sustainability characteristics, the paper will be under pressure, and its internal network of porous fibers will be filled with the polymer substance, so that its internal volume and surface can be more closed. The fiber structure within the paper can be pressed together and locked in a dense state by the dried and cured polymer and obtain a smooth surface.

[0029] In one embodiment, the paper substrate may have a high density, for example at least 800 kg / m 3 , for example at least 900 kg / m 3 , for example at least 1000 kg / m 3 high density.

[0030] The paper substrate may be calendered, such as super calendered. The purpose of the calendering operation is to further provide the paper substrate with a lower surface roughness and a higher density, such as at least 800 kg / m 3 , for example at least 900 kg / m 3 , for example at least 1000 kg / m 3 The paper substrate preferably has a density higher than 900 kg / m 3 Density, for example, higher than 1000 kg / m 3 , to provide a substrate and carrier that is as stable and thin as possible, which is used to further apply a gas barrier coating to withstand the various challenges encountered in the field of liquid carton packaging. These challenges include, but are not limited to, packaging of oxygen-sensitive heavy flowable products, strain on various materials during conversion and manufacturing into multi-layer laminated packaging materials, filling and forming and sealing operations in packaging machines, and handling and distribution of filled and sealed packaging containers in various climates and conditions. This high-density paper substrate provides a stable and durable support for the gas barrier coating applied in this liquid packaging laminate with a thickness of only a few microns or even nanometers (e.g., less than half a micron).

[0031] The paper substrate may also (or as an alternative to impregnation) have a base coating comprising a polymer applied to the top side of the paper substrate, i.e., beneath 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 as in the impregnation process, to further modify the surface of the paper substrate.

[0032] In another embodiment, the base coating composition may comprise a polymer binder having a Tg of -3°C or less, such as -10°C or less, such as -15°C or less, such as -20°C or less. The polymer binder may be an acrylic or methacrylic homopolymer or copolymer. Other suitable polymer binders in the coating composition for the coating in stretchable paper and paperboard applications may be polyurethane-based binders, vinyl acetate-based binders, and polyester resins having 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 and / or to give any further coating or layer applied on the base coating surface a better quality by forming a bridge for better bonding with the paper substrate having an increased breaking strain in the machine direction (e.g., more than 3%).

[0035] The basecoat may be applied by a suitable aqueous dispersion application method followed by drying to evaporate the water. The basecoated and dried substrate may then be calendered.

[0036] The base coating can be very thin, for example from 0.5 to 3 g / m 2 , for example from 0.5 to 2 g / m 2 , for example from 0.5 to 1.5 g / m 2 , for example from 0.5 to 1 g / m 2 The base coating may or may not provide some further oxygen barrier properties inherent to the material used. For example, a thin base coating of starch or carboxymethyl cellulose is used to provide a smooth and closed surface on a paper substrate without affecting any significant inherent gas barrier properties.

[0037] According to a second aspect of the present invention, a paper substrate coated with a gas barrier is provided, which is used as an oxygen-sensitive product (such as oxygen-sensitive food or water), for example, as a gas barrier material in a laminated packaging material for liquid, semi-liquid or viscous food 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, with a total coating thickness of 2 to 5000 nm, for example 2 to 4000 nm.

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

[0039] In one embodiment, the top surface of the paper substrate is coated to a dry coating layer having a thickness of 100 to 5000 nm (0.1 to 5 μm), e.g., 100 to 4000 nm (0.1 to 4 μm), e.g., 300 to 3500 nm (0.3 to 3.5 μm), e.g., 300 to 3000 nm (0.3 to 3 μm), wherein the gas barrier material comprises a polymer, e.g., a binder polymer or a coating polymer.

[0040] The gas barrier material may include 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 lignocellulose derivative compounds. In one embodiment, the polymer is of fully renewable (i.e., non-fossil-based) origin.

[0041] In a more specific embodiment, the gas barrier material may include a polymer selected from the group consisting of vinyl alcohol polymers and copolymers, such as a polymer selected from the group consisting of polyvinyl alcohol, PVOH and ethylene vinyl alcohol, EVOH, starch and starch derivatives, xylan, xylan derivatives, nanofiber cellulose / microfiber cellulose, NFC / MFC, nanocrystalline cellulose, NNC and a mixture of two or more thereof.

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

[0043] The oxygen barrier properties are further improved when the paper substrate is first impregnated and then further coated with a conventional coating (which may be very thin but still provide excellent gas barrier properties in this combination). The gas barrier properties of thin coatings, such as micron thickness coatings provided by dispersion or solution coating of gas barrier compositions, or nanometer thickness coatings formed, for example, by vapor deposition coating processes such as PECVD, PVD, CVD and atmospheric plasma processes, are enhanced and protected by the action of the impregnated and pore-filled paper substrate. In addition, due to the filling of voids and the smoothing effect of the polymer, a lower surface roughness of the impregnated paper substrate can be obtained, thereby greatly improving the quality of the subsequently applied gas barrier coating, thereby obtaining fewer pinholes and a more uniform thickness. Therefore, when impregnated and / or base coated and then coated with a gas barrier material coating, the use of stretchable paper substrates in laminated packaging materials and packaging for oxygen barrier purposes provides further and 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 (e.g. oxygen-sensitive foods for food, such as liquid, semi-liquid or viscous foods or water), comprising the paper substrate of the first use aspect, or comprising the further gas barrier-coated paper substrate of the second aspect. The laminated packaging material further comprises a main body layer of paper or paperboard or other cellulose-based 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 laminated packaging material may therefore also include a main body layer of paper or paperboard or other cellulose-based material, a first outermost liquid-tight material layer, a second innermost liquid-tight material layer, and a paper substrate or a gas barrier-coated paper substrate disposed inside the main body layer of paper or paperboard, between the main body layer and the second innermost layer. The second innermost liquid material layer may also 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 (e.g., liquid, semi-liquid or viscous foods or water), which comprises the laminated packaging material of the third aspect, and is intended to be used for packaging oxygen-sensitive foods. Specifically, 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 made of the laminated packaging material of the present invention, and according to another embodiment, it is made entirely of the laminated packaging material.

[0047] The use of paper substrates as described above, and providing such paper substrates with a further gas barrier coating, enables a significant improvement in the gas barrier properties in laminated packaging materials and packaging containers made therefrom, and may also impart improved repulpability and recycling properties, i.e. increased environmental sustainability.

[0048] Generally speaking, the use of paper substrates in such laminates and packaging provides a greater proportion of fiber content that is both renewable, ie, non-fossil-derived, and can be recovered for recycling to convert old materials into creating new materials.

[0049] Additionally, in such materials and packaging, paper substrates used to carry thin gas barrier material coatings of three or four microns or less can also provide improved robustness of laminated pre-cut apertures, i.e., apertures pre-cut in the bulk layer but subsequently laminated together with all other layers of the laminate including the paper substrate. Detailed Description

[0050] The term "long-term storage" in connection with the present invention means that the packaging container should be able to maintain the quality of the packaged food, i.e. nutritional value, hygienic safety and taste, under certain conditions, for at least 1 or 2 months, such as at least 3 months, preferably longer, such as 6 months, for example 12 months, or longer under ambient conditions.

[0051] The term "package integrity" generally refers to package sealing, i.e. the resistance of the packaging container to leakage or breakage. The term covers the resistance of the package to the intrusion of microorganisms (such as bacteria, dirt and other materials) that may spoil the filled food and shorten the expected shelf life of the package.

[0052] One major contribution to the integrity of a package of a laminated packaging material is provided by good internal adhesion between adjacent layers of the laminate. Another contribution comes from the material's resistance to defects, such as pinholes etc. within each material layer itself, and yet another contribution comes from the strength of the sealing seam by which the materials are sealed together when forming the packaging container. With respect to the laminated packaging material itself, the integrity properties focus mainly on the adhesion of the individual laminate layers to their adjacent layers and the ability to withstand thermal and mechanical loads (e.g. during folding and sealing) without rupture, as well as on the quality of the individual material layers. With respect to the sealing of the package, the integrity focuses mainly on the quality of the sealing seam, which is ensured by a well-functioning and robust sealing operation in the filling machine, which in turn is ensured by properly adjusted heat sealing properties of the laminated packaging material.

[0053] The term "liquid or semi-liquid food" generally refers to a food with a flowing content, which optionally may contain food pieces. Dairy products and milk, soy, rice, grain and seed beverages, fruit juices, nectars, non-carbonated beverages, water, flavored water, energy drinks, sports drinks, coffee or tea beverages, coconut water, wine, soups, jalapenos, tomatoes, sauces (e.g., such as pasta sauce), beans and olive oil are some non-limiting examples of contemplated foods.

[0054] Examples of other oxygen-sensitive foods that can be packaged and protected with the laminated packaging material of the present disclosure are, for example, dry and / or fatty foods. Examples of fatty foods include cheese, butter, and spreads. Such packaging can be a flow-wrap package or a form, fill, seal (FFS) package, such as in a bag. It can also be packaged in a jar, a tray, a covered spread container, a foldable tube, a clamshell package, a sleeve, an envelope, or a wrapping paper. In these applications, the packaging material is typically subjected to folding or similar types of stress (e.g., wrinkling, stretching), which makes the packaging material based on the paper substrate of the present disclosure particularly suitable.

[0055] The term "sterility" in relation to packaging materials and packaging containers refers to conditions under which microorganisms are eliminated, inactivated or killed. Examples of microorganisms are bacteria and spores. When a product is aseptically packaged in a packaging container, an aseptic process is usually used. In order to maintain continuous sterility during the shelf life of the package, the integrity properties of the package are of course very important. For the long shelf life of filled foods, it may also be important that the package has barrier properties to gases and vapors, such as oxygen, so that its original taste and nutritional value, such as its vitamin C content, remain intact.

[0056] The term "body layer" generally refers to the thickest layer or the layer containing the most material in a multilayer 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, such as thick paper, paperboard or carton. It may also mean a layer that provides a greater thickness distance in a sandwich structure, which further interacts with a stabilizing face layer having a higher Young's modulus on each side of the body layer to achieve sufficient such mechanical properties, such as bending stiffness, to achieve structural stability of the formed packaging container.

[0057] Thickness measurements were performed by transmission electron microscopy using a Titan 80-300, FEI Instruments. Samples were prepared by ultrathin sectioning on a Leica EMUC6 microtome.

[0058] OTR was measured using a coulometric sensor based Oxtran 2 / 21 (Mocon) device according to ASTM F1927-14 and ASTM F1307-14. See further description of the OTR test method associated with the Examples.

[0059] Thus, there is provided a use of a paper substrate as a gas barrier material in a laminated packaging material for packaging oxygen sensitive foods, such as liquid, semi-liquid or viscous foods or water, wherein the paper substrate has a relative humidity of 30 to 100 g / m 2 measured according to ISO 536:2012. 2 The invention discloses a paper substrate having a basis weight of 1000 g / cm2, a strain at break of 3% or more and 9% in the machine direction measured according to ISO 1924-3:2005, and a Bendtsen surface roughness of 5 to 150 ml / min or less on at least one side measured according to ISO 8791-2:2013. Such a paper substrate having at least one gas barrier coating is also provided.

[0060] Improving the stretchability of paper during papermaking, i.e. improving the strain-at-break properties, can be achieved by refining at high concentrations (e.g. 20-40%, e.g. 25-38%). During this process, the fibers are deformed and the resulting kinks (i.e. more curled fibers) promote the stretchability of the resulting paper.

[0061] Another method is to allow the paper web to dry with little or no restriction on shrinkage during the drying process. This means that the fiber network is created from fibers that are unstretched and in a more relaxed state. When the dried paper is subjected to a tensile force, the fiber network can deform to a certain extent until the fibers reach their breaking point, i.e. their breaking strain point. Sack paper can be produced by this method.

[0062] A third method of increasing the stretchability of paper is to compress the wet paper web in the longitudinal direction of the fibers (i.e., the machine direction of the paper web). This type of compression results in built-in stretch in the machine direction. Paper web machine direction compression can be performed with a Clupak unit (which includes a nip with a rubber blanket) or an Expanda unit (which includes a nip with a steel roll and a rubber roll that rotate at a speed lower than the speed of the paper web). All of the above methods of increasing the stretchability of paper have the advantage that no additional chemicals or stretch-promoting materials need to be added during the papermaking process.

[0063] In the context of the present invention, a twin roll compactor of the type commonly referred to as an Expanda unit is used to increase the stretchability of the paper substrate. Other methods may also be used as a single method or a combination of method steps, depending on the desired level of stretchability and other paper properties.

[0064] The paper web may be dried in drying zones upstream and downstream of the stretchable unit.The moisture content of the web in the stretchable unit may be in the range of 25%-50%, such as 30%-40%, such as 30%-38%.

[0065] In order to provide a paper substrate capable of forming a good oxygen barrier, the number and size of pores can be significantly reduced. By extensive refining of the pulp, the degree of fiber bonding will increase, thereby reducing the porosity. The greaseproof paper produced by such extensive refining has a sufficiently low porosity to provide a grease barrier. Therefore, in the prior art, greaseproof paper is regarded as a potential substrate or carrier for additional gas barrier coatings. However, the resulting pulp has a high dewatering resistance and requires a long time for pulp dewatering, and its manufacturing process is costly and is undesirable during repulping and recycling. In addition, the gas barrier contribution characteristics also need to be further improved. This is also the case for parchment paper, which obtains gelatinized fibers through a sulfuric acid bath during its manufacturing process, which makes the fibers difficult to dewater and repulp, and the parchment obtains an undesirable brittleness.

[0066] A different method of filling the voids in the fiber cellulose material is to use microfibrillar cellulose (MFC) as the main component of the cellulose material in the sheet or film, which also provides some oxygen barrier properties. However, the dewatering resistance of this type of material is also very high, which may cause similar problems in manufacturing and recycling processes. Therefore, for the purpose of the present invention, it is not desirable to use a paper substrate containing a large amount of MFC or other types of nanocellulose in the pulp used in papermaking. In addition, MFC is not suitable as the impregnation composition of the paper being formed and dried, because it forms a gel in an aqueous composition, rather than a solution or a low-viscosity dispersion.

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

[0068] The cellulose fibers of the paper substrate may exhibit a Canadian Standard Freeness CSF value measured according to ISO 5267-2:2001 of above 200 ml, such as 200 ml to 500 ml, such as 200 ml to 450 ml, such as 200 ml to 350 ml, after repulping in a Valmet pulper of type HD400 according to the Valmet repulping method. The Valmet repulping method comprises repulping 0.5 kg of air-dried paper, cut into pieces of 90 x 90 mm (0.09 x 0.09 m), with 15 liters of water at 57 degrees Celsius for 20 minutes in a Valmet pulper at a rotation speed of 3000 rpm. The CSF values ​​of the paper substrates studied here differ significantly from the CSF values ​​of the best known papers in the prior art, which contain a higher content of refined fibers to provide a denser, i.e. less porous, fiber structure in the paper.

[0069] Expressed differently, as a drainage value, the paper substrate, after repulping according to the standard method of ISO 5263-1:2004, may provide a Schhopper-Riegler (°SR) value measured according to ISO 5267-1:1999 of 30 to 50, such as 33 to 50, such as 35 to 45. The SR values ​​of the investigated papers are significantly lower than the SR values ​​of paper substrates used in the prior art.

[0070] Both CSF and SR values ​​measure the dewatering properties of fibers in a cellulosic fiber pulp and indicate how easy or difficult it is to repulp and recover fibers from a paper substrate and, thereby, from a laminated packaging material that includes a paper substrate.

[0071] Following the same reasoning, after repulping according to ISO 5263-1:2004, an extensible paper substrate formed from cellulose fibers may provide an average fines content of less than 40%, such as less than 35%, such as less than 32%, measured with L&W Fibretester+ (ABB, Lorentzen & Wettre, Sweden) according to ISO 16065-2:2014, wherein fines are defined as fiber particles shorter than 0.2 mm. For example, the fines content of oil-proof paper after repulping is usually higher, such as above 40%, such as at least above 35%, because the manufacturing process of such paper uses pulp with a high refined fiber content. A typical lower limit for the average fines content is 15% or 20%.

[0072] The paper substrate used in the present invention may be formed from cellulose fibers comprising at least 50% by dry weight of chemical pulp, such as kraft pulp, i.e. kraft pulp or sulfite pulp, such as at least 75% by dry weight of chemical pulp, such as at least 85% by dry weight of chemical pulp, such as at least 90% by dry weight of chemical pulp, such as at least 95% by dry weight of chemical pulp. Sulfate or sulfite pulp is used to obtain a sufficiently strong paper for downstream processes such as coating (which can be performed at high speeds) and also for conversion and formation of final packaging.

[0073] Sulfate / Kraft pulp may be preferred because it is widely produced in large quantities. However, sulfite pulp may also be useful because it is generally easier to refine than sulfate pulp. A higher degree of fiber swelling can be obtained with sulfite pulp, which is a disadvantage from a drying point of view (higher energy requirements during drying), but an advantage from a density point of view (swelling improves the compliance of the fibers, resulting in a denser paper sheet). Kraft pulp is beneficial for improved repulping in recycling and general dewatering of the fibers. Sulfite fibers generally have a higher proportion of refined fibers, which may have a slightly opposite effect, depending on the amount and degree of refining. According to one embodiment of the present invention, kraft pulp may therefore be preferred.

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

[0075] The benefit of including hardwood pulp is that it collapses relatively easily during refining, while it still allows efficient dewatering in the wire section of the paper machine. The benefit of including softwood pulp is improved runnability of the paper machine and beneficial strength / toughness properties of the resulting paper. The latter property can be improved by high consistency (HC) refining of softwood pulp. HC refining can also increase strain at break values. HC refining refers to refining at a consistency of 20% to 40%, preferably 25% to 38%.

[0076] Such pulp compositions may be advantageous for recycling repulping and general dewatering performance in the papermaking process and for high quality recycled fiber. When the proportion of softwood pulp is relatively high, e.g. at least 60%, e.g. at least 70%, it is advantageous if in the manufacture of paper the Schopper-Riegler (SR) value of the pulp used, measured according to ISO 5267-1:1999, is 25 to 35. Such SR values ​​may promote a sufficiently high density of the paper substrate without causing problems in dewatering and / or recovery, and may be obtained by adjusting the degree of low consistency (LC) refining.

[0077] If the SR value is above 35, it is difficult to dewater the diluted pulp at a sufficient rate in the forming section. If the SR value is below 25, the properties of the final product are generally poor. If the concentration of the diluted pulp is above 0.9%, there is a risk that the paper is too porous and the paper surface is too rough for producing the paper substrate used in the present invention.

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

[0079] The pulp may be diluted to a consistency of 0.1% to 0.5%, such as 0.1% to 0.4%, to reduce fiber flocculation, which reduces the porosity of the ultimately formed paper.

[0080] Preferably, the softwood fibers used for the paper substrate have been subjected to high consistency (HC) refining so that the fibers acquire some inherent stretchability in the paper substrate.

[0081] When softwood pulp is used, it may therefore be subjected to high consistency (HC) refining, i.e. refining at a consistency of 20% to 40%, e.g. 25% to 38%, i.e. the weight concentration of dry fibers in the pulp. The specific energy of the HC refining step may be at least 100 kWh / tonne, e.g. at least 150 kWh / tonne, e.g. 150 to 300 kWh / tonne. The units "tonne" refer to tons of dry fibers.

[0082] The pulp can be bleached, thereby reducing the concentration of elements or compounds that could cause staining and / or odor in the final packaging.

[0083] Thus, paper can be formed by providing a pulp comprising at least 50% by dry weight of chemical pulp (e.g. kraft pulp or sulfite pulp) having a Schopper-Riegler of 25 to 50, such as 25 to 45, such as 25 to 35, diluting the pulp to a low consistency of 0.1 to 0.9%, and 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. The pulp may contain less than 10%, such as less than 5%, pigments or inorganic fillers by dry weight, such as less than 3%, such as less than 1%, such as almost no pigments or inorganic fillers by dry weight, further improving repulpability and dewatering properties. Silica or bentonite used as retention aids, typically in an amount of less than 1 kg per ton of dry pulp, are not considered as inorganic fillers. Thus, according to ISO 2144:2015, the ash content of the pulp is preferably less than 5%, such as less than 3%, such as less than 1%.

[0084] After wet pressing, the web may be dried to about 65% fiber weight percent before entering an extensible unit for compaction in the machine direction.

[0085] According to a specific embodiment, a paper substrate having a top layer and a bottom layer (i.e., a two-layer construction) can be used. With such a paper substrate, its properties can be better tailored to its needs. In such a structure, the properties of the top layer can be tailored to receive another barrier layer, while the properties of the bottom layer can be tailored for strength / toughness. Hardwood pulp can provide an improved surface or for another barrier layer. Softwood pulp can improve the runnability of a paper machine and provide beneficial strength / toughness properties in the resulting paper product.

[0086] For example, the top layer may be formed of at least 50% by dry weight hardwood pulp, such as at least 65% by dry weight hardwood pulp, such as at least 75% by dry weight hardwood pulp to make the top side surface of the paper that can be impregnated and calendered more dense and smooth.

[0087] On the other hand, the bottom layer may be formed from at least 50% by dry weight of softwood pulp, such as at least 65% by dry weight of softwood pulp, such as at least 75% by dry weight of softwood pulp. This may allow for easier dewatering and repulping, or may simply make the paper cheaper to manufacture. If such a back side surface also needs to be impregnated, a larger amount of impregnating composition or impregnating polymer may be required.

[0088] The two-layer paper may include method steps wherein a first wire is used to form a first web which becomes a top layer, and a second wire is used to form a second web which becomes a second layer, and wherein the first web and the second web are stacked together.

[0089] The first web may be formed from a first furnish comprising at least 50% by dry weight hardwood pulp, such as at least 65% by dry weight hardwood pulp, such as at least 75% by dry weight hardwood pulp. The first furnish may have a headbox consistency of 0.12%-0.60%, such as 0.18%-0.35%.

[0090] The Schopper-Riegler (°SR) value of the first furnish in the headbox measured according to ISO 5267-1: 1999 may be 33-45, for example 40-50. Such SR values ​​may promote sufficiently high density without causing dewatering and / or recirculation problems and may be obtained by adjusting the degree of low consistency (LC) refining.

[0091] The second web may be formed from a second furnish comprising at least 50% by dry weight softwood pulp, such as at least 65% by dry weight softwood pulp, such as at least 75% by dry weight softwood pulp. The softwood pulp has preferably been refined at high consistency (HC) (suitable ratios can be discussed above). The headbox consistency of the second furnish may be from 0.06% to 0.40%, such as from 0.10% to 0.25%.

[0092] In one embodiment, the headbox consistency of the second furnish is lower than the headbox consistency of the first furnish.

[0093] The Schopper-Riegler (°SR) value of the second furnish in the headbox measured according to ISO 5267-1: 1999 may be 25 to 35. Such SR values ​​may promote sufficiently high density without causing dewatering and / or recirculation problems and may be obtained by adjusting the degree of low consistency (LC) refining.

[0094] Preferably, the furnish comprises less than 2 wt% inorganic filler, such as less than 1 dry weight% inorganic filler, such as being substantially free of inorganic filler.

[0095] In the manufacture of two-ply papers, an additional intermediate coating or addition of starch or PVOH may optionally be applied before the top and bottom layers are pressed together.

[0096] The density of the paper substrate may preferably be 1050 to 1500 kg / m 3 , for example 1100 to 1400 kg / m 3 , for example 1100 to 1300 kg / m 3 .

[0097] The impregnation composition comprising a polymer in aqueous solution can help lock the fiber network in a locked position upon subsequent calendering and drying.By using such a paper substrate, densification of the paper provides direct and indirect gas barrier properties and can contribute to the successful results of the present invention.

[0098] The tensile strength index of the paper substrate may be at least 90 Nm / g, such as at least 100 Nm / g, such as 90-150 Nm / g in MD, and at least 40 Nm / g, such as at least 50 Nm / g, such as 55-90 Nm / g, such as 60-90 Nm / g in CD. The tensile strength index is measured according to ISO 1924-3:2005.

[0099] A higher tensile strength index can indicate that the paper substrate can be used to withstand web handling forces during coating and laminating operations.

[0100] Preferably, beneficial barrier and recycling properties are obtained without sacrificing strength, such as tensile strength and tear strength.

[0101] After the stretchable unit and compaction operation, the paper web can be dried in a drying section to form a paper substrate having a moisture content of 4% to 7% for subsequent impregnation with an aqueous composition comprising a water-soluble or water-dispersible polymer in a size press or film press operation, etc. The reduction in moisture content before impregnation allows the pores of the web to be filled.

[0102] The impregnation step may include adding an aqueous composition comprising an impregnating polymer to at least the top side of the paper substrate, or to each side of the paper substrate. The top side of the paper substrate is the side to be further coated with the gas barrier coating and is typically the smoothest surface of the paper substrate.

[0103] The viscosity of the aqueous composition measured at 60°C may be 55-90 mPa*s. This relatively low viscosity facilitates the penetration of the polymer into the fiber web. The concentration of the impregnating polymer in the aqueous composition is preferably 7.0%-13.0% (w / v), such as 8.0%-12.0% (w / v). The 60°C viscosity measurement is preferably carried out using a Brookfield rotational viscometer equipped with a No. 3 spindle at 100 rpm.

[0104] To promote further densification, the impregnated paper may then be moistened to a moisture content of 10-30%, such as 11-20%, and then calendered in a calendering unit comprising at least two heated nips. The calendering operation may preferably be carried out in at least one supercalender having 8 to 20 calendering rolls, such as 9 to 19 rolls, such as 11 to 17 rolls, and some moisture, such as a moisture content of 11 to 20%, may be applied to the paper web again before the calendering operation. The total nip pulse of the supercalendering step may be at least 600 kPa*s. The surface temperature of the heated calendering rolls may be 120-160°C.

[0105] The moisture content of the paper web facilitates the calendering operation, providing increased density, reduced porosity and improved surface properties in the final paper.

[0106] During calendering, the paper is dried. Overdrying can be achieved by additional drying immediately after calendering, i.e. before winding. An air dryer can be used for this additional drying. With this arrangement, moisture contents below 4% can be achieved, which can be advantageous for subsequently performed coating operations, such as vapor deposition coating operations.

[0107] In one embodiment, therefore, a suitable paper substrate for use in the present invention can be further obtained by impregnating the formed paper with an aqueous impregnation composition comprising a water-soluble or water-dispersible polymer in a concentration of 5 to 20 weight percent (e.g. 5 to 15 weight percent, e.g. 7 to 13 weight percent, e.g. 8 to 12 weight percent), by a size press or film press operation, etc., and subsequently calendering and drying the thus impregnated paper to a resulting density of more than 800 kg / m 3 , for example, higher than 900kg / m 3 , for example, higher than 1000kg / m 3 Such high density can preferably be obtained by super calendering. In one embodiment, the density is at least 1050 kg / m 3 , for example at least 1070kg / m 3 The upper limit of density is usually 1400kg / m 3 , for example 1300kg / m 3 .

[0108] By impregnating the paper with an aqueous impregnating composition comprising one or more of the polymers listed above, the internal porous network of cellulose fibers below the surface of the paper is filled and surrounded by the polymer, so that when the paper is calendered, the polymer will hold the fiber body of the paper closer together, with fewer voids between them and in a locked position (by virtue of the polymer being slightly more elastic in its nature than the cellulose fibers), thereby avoiding open channels between the fibers to pass through the material when the material is mechanically abused (e.g. folded or twisted). Firstly, this has a direct effect on gas or oxygen molecules trying to diffuse through the porous material, by the pore filling effect of the polymer, which should have a good affinity for cellulose, and by the polymer tying the fibers together in a locked position. There may also be an indirect effect on improving the gas barrier properties of the paper substrate, because the pore filling polymer flattens the irregularities of the fiber surface of the paper, so that the surface is prepared to prepare a non-porous and unique interface for further aqueous dispersion barrier coating or polymer extrusion coating. This eliminates any trapped air at the interface, which otherwise may cause coating defects or compromise the air tightness of the laminate.

[0109] In one embodiment, suitable impregnation compositions may comprise a major portion (i.e., an amount of at least 50% by weight) of an impregnation polymer selected from PVOH, EVOH starch, and starch derivatives, because these materials are relatively easy to handle and prepare low viscosity solutions suitable for impregnation, and they are also relatively cost-effective. Impregnation compositions that primarily comprise (i.e., at least 50% by weight) an impregnation polymer selected from PVOH and EVOH are preferred, because they generally provide better oxygen barrier properties among such polymers.

[0110] The degree of hydrolysis of PVOH can be 96%-100%, such as 97%-100%, such as 97%-99%. PVOH with a high degree of hydrolysis is less sensitive to water and is preferred in both production and use. The weight average molecular weight (Mw) of PVOH is preferably less than 100,000 g / mol, such as 10,000-90,000 g / mol, such as 30,000-80,000 g / mol. This relatively low Mw is preferred in the impregnation process because it has a relatively low viscosity at a relatively high concentration. Low Mw PVOH is more likely to penetrate into the fiber web or paper substrate rather than staying on the surface of the paper.

[0111] The viscosity of the PVOH is preferably below 20 mPa*s, such as 5-16 mPa*s, such as 6-13 mPa*s, when measured according to DIN 53015.

[0112] The degree of polymerization (DP) of PVOH is preferably below 3000, for example 1000-2000. DP can be determined from the viscosity average degree of polymerization derived from the viscosity in water. In this case, the viscosity is measured in a 4% aqueous solution at 20°C and determined by a Brookfield synchronous motor rotation type viscometer.

[0113] An example of a suitable PVOH is Poval 10 / 98 from Kuraray, 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 Poval 6 / 98 from Kuraray, which has a viscosity of 6 mPa*s and a degree of hydrolysis of 98%.

[0114] In some applications, 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 EVOH low viscosity formulation is AQ-4104.

[0115] The impregnation composition may comprise a large amount of nanocrystalline cellulose, "NCC" (or "CNC"), or a blend of NCC with starch or PVOH, and adjusted to a viscosity suitable for impregnation. Since NCC is a cellulose and can also provide good oxygen barrier properties, it constitutes an attractive future barrier material in packaging, although it may currently be a less cost-effective alternative for bulk use.

[0116] Nanocrystalline cellulose, NCC, is a form of nanocellulose, but is different from "microfibrillar cellulose", "MFC" (CMF) or "nanofibrillar cellulose", NFC (CNF). Although the term "MFC" may often be incorrectly used for all types of fibrillated cellulose, a more scientific view is that "MFC" should refer to nanoscale cellulose fibrils or fibril aggregates with at least one dimension less than 100nm.

[0117] Thus, the MFC may contain longer particles, so called "fibrils", having a width of 10-100 nm and a length of at least 1 μm, such as up to 10 μm, such as longer than 10 μm.

[0118] MFC and NFC both have an aspect ratio of 50 or more, while NCC may be defined as having an aspect ratio below 50, for example according to the draft TAPPI specification WI3021.

[0119] The term "NCC" is used for shorter particles and "rod-like" particles having a width of 3-50 nm and a length of 100 to 1000 nm, such as 100 to 900 nm, such as 100 to 500 nm, such as 100 to 200 nm. For the purpose of impregnation and filling the pores in the forming paper, the preferred size of the NCC may be 100 to 500 nm in length, such as 100 to 200 nm and have a small width of 3 to 50 nm, which means that most of the NCC particles in the composition should have this size.

[0120] The amount of impregnated polymer may be 0.5 to 4 g / m 2 , for example 1 to 3 g / m 2 Although the top side may need to be impregnated with at least 1.5 or 2 g / m 2 The impregnation composition may comprise essentially only water and the impregnation polymer.

[0121] Depending on the choice of the back cellulose fiber type, the back side may also be impregnated. The polymer may be completely impregnated through the cellulose interstices throughout the thickness of the paper, or only partially impregnated into the center / middle of the paper thickness. For optimal gas barrier contribution of the paper substrate, it is believed that as much impregnation of the polymer as possible is desired. However, in order to make the paper usable in a recycling process after use, the amount of impregnated polymer may need to be balanced with the repulping properties of the paper. It may also be preferred to impregnate both sides of the paper to avoid curling of the dried paper substrate causing problems in subsequent coating and lamination operations.

[0122] Thus, "impregnation" means that the impregnation composition and the impregnation polymer have penetrated the fiber web to a large extent, i.e., have penetrated the cellulose fibers of the paper substrate to a large extent. However, this does not necessarily mean that the fiber web has been completely saturated with the polymer in the thickness direction. Thus, the paper substrate may include unfilled pores, especially in the middle. Thus, it is possible to use a cellulose fiber web containing 0.3 to 4.0 g / m 2 , for example 0.5 to 3.0 g / m 2 The paper substrate and the fiber web are impregnated with the impregnating composition of the impregnating polymer in an amount of the impregnating polymer.

[0123] To facilitate application and impregnation of the polymer, it is water-soluble or water-dispersible.

[0124] The extent and depth of the impregnated polymer through the thickness of the paper substrate can be studied by taking sectioned samples of the paper and studying them in a SEM microscope. Sectioning can be done using, for example, a cryo-tome.

[0125] The type of polymer used in the impregnation composition can be determined by FTIR spectroscopy or a combination of FTIR and other spectroscopy methods.

[0126] According to one embodiment, a paper substrate is used, according to one embodiment, a paper substrate is used, which is impregnated and then calendered to a roughness of the top surface measured according to SS-ISO8791-2:2013 of less than 100 ml / min Bendtsen, such as less than 80 ml / min Bendtsen, such as 7 to 80 ml / min Bendtsen, such as 7 to 50 ml / min Bendtsen, such as 7 to 30 ml / min Bendtsen, such as 7 to 25 ml / min Bendtsen, such as 7 to 20 ml / min Bendtsen. A typical lower limit may be 5 or 7 ml / min Bendtsen.

[0127] A different measure of surface roughness is the Parker Printed Surface (PPS) roughness, which should exhibit values ​​in the range of 1.0 to 2.0 μm, for example 1.2 to 1.8 μm, such as measured according to SS-ISO 8791-4:2013.

[0128] Furthermore, the Gurley value of the paper substrate according to ISO 5636-5:2013 may be higher than 220 seconds. This means that the surface of the high-density paper substrate is closed, ie it does not trap any air or oxygen between the fibers on the surface.

[0129] The lower surface roughness provides a perfect interface for the subsequently applied adjacent layers and coatings, while reducing the number of defects in the coating, such as pinholes and inhomogeneities. As a result, the coating or the additional layer can be produced with higher quality, or with lower thickness, or both. For the same coating thickness of the gas barrier coating, better oxygen barrier properties are thus obtained in the coating itself.

[0130] The impregnation step is preferably carried out by a size press or a film press. A film press is the most preferred equipment. If the film press is of the double-sided type, the back side of the paper web can also be impregnated to further reduce the porosity of the paper substrate finally provided, and / or for curl control. The film press can be an OptiSizer Film (Valmet) or a SpeedSizer (Voith). After film pressing, the web is dried to a moisture content of 12%-25%, preferably about 15%. The drying is preferably carried out by non-contact drying, preferably using hot air, until the primer does not adhere to the hot metal surface, and then by steam-heated drum drying. Since the impregnation composition is impregnated only from one side of the paper, the paper may curl. Therefore, impregnation from both sides of the paper can better provide a flat and balanced paper substrate.

[0131] Thus, the paper substrate may also be impregnated at the opposite backside surface of the paper with an impregnation composition comprising an impregnation polymer selected from the same group as for the topside surface of the paper. The paper may be impregnated from the backside and subsequently calendered to a roughness of the backside surface measured according to SS-ISO 8791-2:2013 of less than 200 ml / min Bendtsen, for example less than 150 ml / min Bendtsen.

[0132] Therefore, the amount of impregnated polymer at the top side of the paper substrate may be 0.3 to 4 g / m 2 , for example 0.3 to 3 g / m 2 , for example 0.3 to 2 g / m 2 , for example 0.5 to 3 g / m 2 , for example 0.5 to 2 g / m 2 .

[0133] 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 crosslinking agent, such as glyoxal, in a weight ratio of 100:3 to 100:12, such as 100:3 to 100:9. Preferably, the impregnation composition is an aqueous solution of a polymer having a low molecular weight and thus a low viscosity. An example of a suitable formulation for PVOH is a low viscosity grade of Kuraray An example of a low viscosity EVOH formulation is Kuraray's AQ-4104. The degree of hydrolysis of PVOH should be as high as possible, for example 98% or 99%, and low molecular weight PVOH may also be preferred for the best possible impregnation effect. In another embodiment, the impregnating polymer may be an aqueous solution of starch or starch derivatives, carboxymethyl cellulose, etc. Anionic starch solutions are suitable due to their good affinity for cellulose.

[0134] In one embodiment, the impregnating polymer for the back surface of the paper may also be selected from aqueous solutions of polyvinyl alcohol, PVOH and ethylene vinyl alcohol, EVOH, optionally further comprising a crosslinking agent, such as glyoxal, for example, the weight ratio of PVOH to glyoxal is 100:3 to 100:12, such as 100:3 to 100:9.

[0135] In another embodiment, the impregnated polymer for the back side surface of the paper can be changed to an aqueous solution of starch or starch derivatives, carboxymethyl cellulose, etc. This is beneficial for the back side surface of the paper substrate not to stick to the top side surface when it is wound on a reel for transportation and storage. In addition, it can also prevent the paper roll from curling during the production process.

[0136] In addition to the impregnating polymer, the impregnating composition may also contain a small amount of a mineral selected from clay (e.g. bentonite, kaolin or barite) and talc, CaCO 3 Inorganic particles from the group consisting of silica particles. For better impregnation performance, the particle size should be as small as possible, but still support filling the gaps between the cellulose fibers together with the impregnating binder polymer of the impregnating composition.

[0137] The impregnation composition may penetrate a substantial portion of the thickness of the paper substrate web. Impregnation may be performed from the top and back sides of the paper, partially or completely into the center of the paper.

[0138] In one embodiment, the grammage of the impregnated paper substrate may be 30 to 90 g / m 2 , for example 30 to 80 g / m 2 , for example 30 to 70 g / m 2 , for example 30 to 66 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 2 .

[0139] The thickness of the impregnated paper substrate may be 30 to 95 μm, such as 30 to 85 μm, such as 30 to 75 μm, such as 30 to 70 μm, such as 35 to 65 μm, such as 35 to 60 μm, such as 35 to 55 μm.

[0140] It has been found that for certain applications, such as for liquid-tight packaging of wet or liquid or viscous products, it may be advantageous to use a paper substrate that is as thin as possible, since less polymer may be required in the adjacent liquid-tight or heat-sealable layer. Such thermoplastic layers are typically laminated to the paper substrate by melt extrusion, such as a polyolefin layer or other thermoplastic layer.

[0141] The paper substrate may also be coated with a preliminary base coating on its top side surface, or as an alternative to impregnation. Thus, the paper substrate may be provided with a thin continuous layer and a surface base coating comprising a polymer applied to the top side of the paper substrate and underneath the subsequently applied gas barrier coating. The base coating composition may comprise one or more of the same polymers 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. the same polymers as used for impregnation, to further improve the surface of the paper substrate.

[0142] Since the wet base coating composition is only primed on one side of the paper, the paper may curl. Priming on both sides of the paper may better provide a flat, balanced paper substrate.

[0143] Thus, the paper substrate may also be coated on the opposite backside surface of the paper with a base coating composition comprising a polymer selected from the same group as used for the base coating on the topside surface of the paper.

[0144] Thus, there is provided a use of a paper substrate as a gas barrier material in a laminated packaging material for packaging oxygen-sensitive foods, such as liquid, semi-liquid or viscous foods or water, wherein the grammage of the paper substrate is 30 to 100 g / m 2 measured according to ISO 536:2012. 2, a strain at break in the machine direction measured according to ISO 1924-3:2005 of higher than 3%, and a Bendtsen surface roughness of at least one side measured according to ISO 8791-2:2013 of lower than 150 ml / min, wherein the paper substrate is impregnated or base-coated with a polymer, for example selected from the group consisting of polyvinyl alcohol, PVOH, ethylene vinyl alcohol, EVOH, starch, starch derivatives, carboxymethyl cellulose, CMC or other cellulose ethers.

[0145] The dry weight of the impregnated or substrate coated polymer may be from 0.5 to 4 g / m 2 , for example 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 .

[0146] In another embodiment, the base coating composition may include a polymer binder having a Tg of -3°C or less, such as -10°C or less, such as -15°C or less, such as -20°C or less. The polymer binder may be an acrylic or methacrylic homopolymer or copolymer. Other suitable polymer binders in the coating composition for coatings in stretchable paper and paperboard applications may be polyurethane-based binders, vinyl acetate-based binders, and polyester resins having a Tg < -3°C.

[0147] 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.

[0148] The purpose of the base coating is to provide a smoother surface to the paper substrate by forming a bridge for better bonding with the paper substrate having an increased breaking strain in the machine direction and / or to give any further coatings or layers applied to the base coated surface a better quality.

[0149] Application of the base coating may be carried out by a suitable aqueous dispersion application method followed by drying to evaporate the water. The base coated and dried substrate may then be calendered.

[0150] There is a clear difference between impregnation and coating of similar polymer compositions. Impregnation is primarily intended to place the polymer composition inside the paper, i.e., below the surface, and is achieved by applying a wet polymer composition and subsequently or simultaneously applying pressure to the wet-applied surface. Coating operations using the same or similar polymer compositions are carried out by wet application and direct drying at a high moving speed of the paper substrate web to prevent the liquid of the wet-applied polymer composition from being absorbed rather than evaporated. The goal is to provide a completely covered coating that extends over the entire surface of the substrate and is continuous and substantially uninterrupted. Even if not completely perfect, this base coating provides a good base or foundation for the formation of a subsequently applied thin but continuous, more perfect and uninterrupted gas barrier coating. It has been seen that impregnation and base coating can impart improved substrate properties to paper substrates in different ways, yet result in similar improved results for the subsequently applied gas barrier coating. A continuous and uninterrupted gas barrier coating is very important for the final gas barrier properties of the coating in the laminate. Even though it may be very thin, it can provide the necessary and lasting gas barrier properties required if it is free of defects such as pinholes and cracks. For paper substrates that are only impregnated, more gas barrier coating may have to be applied to obtain a good gas barrier effect, while base-coated paper substrates can subsequently have a thinner gas barrier coating applied. On the other hand, the base coating may have to be of slightly different quality, for example, including some inorganic particles or having a higher viscosity during the wet application operation.

[0151] A gas barrier coated paper substrate for a gas barrier material in a laminated packaging material for oxygen sensitive products can be provided by using any of the above embodiments of the paper substrate of the first aspect of the invention, wherein its top side surface has 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 scrap or waste when used laminated packaging materials comprising such coatings are recycled in existing cellulose fiber recycling streams, and they do not consume too much material relative to the benefits they provide.

[0152] At least one gas barrier coating can be formed by applying and then drying a dispersion or solution of an aqueous composition of at least one gas barrier material. The gas barrier coating forms a continuous and uninterrupted layer of gas barrier material on the surface of the paper substrate. This is achieved by impregnating or priming the paper substrate with an impregnation or base coating polymer material composition. The impregnated or primed paper substrate has a smoother and / or more closed surface, so that the subsequently applied gas barrier coating can be applied at a very low thickness, but still has a high-quality coating to obtain a uniform surface and thickness, as well as uniformity throughout its thickness and lateral extension of the continuous coating.

[0153] According to one embodiment, the top side surface of the paper substrate may be coated to a dry coating thickness of 100 to 5000 nm (0.1 to 5 μm), such as 100 to 4000 nm (using gas, such as from 0.1 to 4 μm), such as from 300 to 3500 nm (from 0.3 to 3.5 μm), such as from 300 to 2500 nm (from 0.3 to 2.5 μm), with a barrier material comprising a polymer.

[0154] The gas barrier material may comprise a polymer selected from the group consisting of vinyl alcohol polymers or copolymers, such as polyvinyl alcohol, PVOH, or ethylene vinyl alcohol, EVOH, and polysaccharides or polysaccharide derivatives. Suitable polysaccharides or polysaccharide derivatives may be selected from the group consisting of starch, starch derivatives, chitosan, chitosan derivatives, cellulose, cellulose derivatives, and lignocellulose derivative compounds. In one embodiment, the polymer is of renewable (i.e., non-fossil-based) origin.

[0155] In a more specific embodiment, the gas barrier material may include a polymer selected from the group consisting of vinyl alcohol polymers and copolymers, such as a polymer selected from the group consisting of polyvinyl alcohol, PVOH, ethylene vinyl alcohol, EVOH, starch and starch derivatives, xylan, xylan derivatives, nanofiber cellulose / microfiber cellulose, NFC / MFC, nanocrystalline cellulose, NNC and a mixture of two or more thereof.

[0156] 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 with only very low coating amounts (i.e. very thin coatings, e.g. less than 1 g / m 2 or less than 1.5 μm) to provide oxygen barrier properties with the aim of providing a gas barrier material that can be recycled in a cellulose fiber recycling stream without leaving behind undesirable amounts of waste material, so-called "scrap".

[0157] Such thin coatings are obtained by coating with a dispersion or solution of the gas barrier material contained in the aqueous gas barrier composition and subsequent drying, and cannot be applied at such thin coating thicknesses by any alternative method (e.g. extrusion coating). Polymers and substances can be applied as solutions or dispersions in organic solvents other than water, but such methods are generally not relevant to providing future environmentally sustainable packaging materials.

[0158] In a preferred embodiment, 0.5 to 3.5 g / m 2 , for example 1 to 3 g / m 2 A PVOH coating is applied to the top surface of the paper substrate.

[0159] Furthermore, when the gas barrier material coating is formed by coating and then drying a dispersion or solution of a gas barrier composition, it may also contain a layered compound such as nano-sized layered clay, talc or CaCO 3 .

[0160] Thus, a gas barrier coated paper substrate for use in a laminated packaging material for packaging oxygen sensitive foods, such as liquid, semi-liquid or viscous foods or water, can be provided, wherein the grammage of the paper substrate is from 30 to 100 g / m 2 as measured according to ISO 536:2012. 2 , a strain at break in the machine direction higher than 3% measured according to ISO 1924-3:2005 and a Bendtsen surface roughness of less than 150 ml / min on at least one side measured according to ISO8791-2:2013, wherein in a first step the paper substrate is impregnated or base-coated 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.

[0161] Preferably, the impregnating or substrate coating polymer is selected from starch, starch derivatives, carboxymethyl cellulose, CMC or other cellulose ethers and is present in an amount of 0.5 to 4 g / m 2 , for example 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 The gas barrier coating may then be applied on top of the impregnated or substrate-coated top side of the paper as a continuous, uninterrupted coating with a total thickness of 2 to 4000 nm (4 μm), such as 2 to 3000 nm (3 μm).

[0162] According to another embodiment, the gas barrier coated 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 on its top surface. More specifically, the vapor deposited coating can be selected from aluminum metallization coatings and aluminum oxide AlO x Preferably, it is an aluminum metallization coating.

[0163] In another embodiment, the gas barrier coated paper substrate has on its top side surface: a first continuous gas barrier material coating formed by coating a dispersion or solution of an aqueous gas barrier composition and subsequent drying, and a further vapor deposited gas barrier material coating applied on the first coating, the gas barrier material being formed of a gas barrier material selected from metals, metal oxides, inorganic oxides and amorphous diamond-like carbon. Thus, the coated paper substrate with the applied gas barrier material coating is subsequently further coated by a vapor deposition coating having a thickness of 2 to 200 nm, such as 2 to 150 nm, such as 2 to 100 nm, such as 5 to 80 nm, such as 5 to 50 nm, such as 2 to 45 nm.

[0164] It is also possible to provide a coated paper substrate, wherein the back side of the paper substrate is also coated with at least one coating of a gas barrier material as defined in any of the above embodiments.

[0165] The vapor deposited barrier coating that is ultimately coated onto the top side surface of the paper substrate is applied by physical vapor deposition (PVD) or chemical vapor deposition (CVD), such as by plasma enhanced chemical vapor deposition (PECVD).

[0166] Generally speaking, below 5 nm, the barrier properties may be too low to be useful, and above 200 nm, such as above 100 nm, such as above 50 nm, depending on the type of vapor deposited coating, the barrier coating may be less flexible and therefore more susceptible to cracking when applied to a flexible substrate, and also more costly.

[0167] Other examples of vapor deposited coatings are aluminum oxide (AlO x 、Al 2 O 3 ) and silicon oxide (SiO x Generally speaking, PVD coatings of such oxides would be less suitable for incorporation into packaging materials by lamination, whereas metallization layers made by PVD are well suited for flexible packaging laminates.

[0168] Typically, due to the nature of the metallization coating process used, aluminum metallization layers inherently have a thin surface portion composed of aluminum oxide.

[0169] In one embodiment, such an aluminum metallization layer has been applied to an optical density (OD) of 1.8 to 3.5, preferably 1.9 to 2.5. When the optical density is lower than 1.8, the barrier properties of the metallized film may be too low. On the other hand, at too high a metal thickness, the metallization layer may become brittle, and the thermal stability during the metallization process may be lower due to the higher heat load when the substrate film is metallized for a longer time. The coating quality and adhesion may be negatively affected. In one embodiment, taking into account the flexibility of the applied metallization coating and the efficiency of the coating operation, the thickness of the applied metal deposition coating is 10 to 200 nm, such as 10 to 150 nm, such as 10 to 100 nm, such as 10 to 95 nm, such as 10 to 80 nm, such as 10 to 50 nm, which is equivalent to less than 1-3% of the aluminum metal material present in conventional thickness aluminum foil (e.g., 6-9 μm) for packaging.

[0170] Other coatings can be applied by plasma enhanced chemical vapor deposition methods (PECVD), in which the vapor of a compound is deposited onto the substrate in a more or less oxidizing environment. Silicon oxide coatings (SiOx) can also be applied, for example, by a PECVD process, and very good barrier properties can then be obtained under certain coating conditions and gas recipes.

[0171] DLC defines a class of amorphous carbon materials (diamond-like carbon) that exhibit some typical properties of diamond. Preferably, hydrocarbon gases, such as acetylene or methane, are used as process gases in the plasma for producing amorphous hydrogenated carbon barrier coatings, i.e. DLC, applied by PECVD vacuum processes. DLC coatings applied by PECVD under vacuum can provide good adhesion to adjacent polymer or adhesive layers in laminated packaging materials. Particularly good adhesion to adjacent polymer layers is obtained using polyolefins and in particular polyethylene and polyethylene-based copolymers.

[0172] The total applied thickness of the continuous covering gas barrier coating may be up to 5 μm, such as 4 μm, such as 3.5 μm.

[0173] Therefore, the laminated packaging material for packaging oxygen-sensitive products (e.g., oxygen-sensitive foods, such as liquid, semi-liquid and viscous foods or water) of the third aspect comprises a paper substrate as defined in any one of the embodiments of the first aspect, or a barrier-coated paper substrate according to any one of the embodiments of the second aspect, and further comprises a main body layer of paper, paperboard or other cellulose-based material, a first outermost liquid-tight material layer and a second innermost liquid-tight material layer. The second innermost layer may also be a liquid-tight, heat-sealable material.

[0174] Therefore, the laminated packaging material also includes a main layer of paper or paperboard or other cellulose-based material, and has a paper substrate or a gas barrier-coated paper substrate or a coated high-density paper substrate laminated between the main layer and a second innermost layer, which second innermost layer will be directed to the interior of the container formed by the laminated packaging material.

[0175] When the paper substrate is also coated with a vapor deposited coating (which typically also adds some further water vapor barrier properties to the coated paper substrate), there is no need to add additional layers of gas or water vapor barrier material to the overall laminate structure.

[0176] When the top side surface of a paper substrate has a first coating of a gas barrier material formed by coating and subsequently drying a dispersion or solution of an aqueous gas barrier composition (e.g. PVOH), and also has a vapor deposited coating of a gas barrier material selected from metals, metal oxides, inorganic oxides and amorphous diamond-like carbon (e.g. an aluminum metallization coating) applied to the first coating, a very good material is obtained which can be used to replace conventional aluminum foil of micron thickness (greater than 5 μm, e.g. 6 μm) as the sole oxygen barrier material in a laminated packaging material. The vapor deposited coating or metallization thus applied can of course be further coated with another wet applied coating or vapor deposited coating of the same or different chemistry to further improve the barrier properties, although this is not necessary and may further increase costs.

[0177] In another embodiment, the paper substrate or coated paper substrate can be passed through 0.5 to 5 g / m 2 The intermediate adhesive composition is laminated to the main body layer, and the intermediate adhesive composition includes an adhesive 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. Such a low amount of intermediate adhesive composition can only be applied by aqueous dispersion or solution coating of polymer adhesive, and cannot be applied by extrusion coating or extrusion lamination of polymer melt. Since the surfaces of the layers to be bonded are all made of cellulose, wet lamination is carried out by absorbing an aqueous medium into each cellulose layer, thereby forming a thin and dry adhesive layer at the interface between the two layers.

[0178] The laminated packaging material may have a preformed polymer film laminated between the paper substrate or coated paper substrate and the second innermost liquid-tight material layer to improve the robustness of the mechanical properties of the laminated packaging material. The preformed film has a higher degree of orientation of the polymer from which it is made and therefore has different mechanical properties from layers of the same or corresponding polymer that are only extrusion coated or extrusion laminated. Therefore, by incorporating such a film into the structure, the laminated material can become stronger and better resist any downstream tough treatment of the material. It is best to avoid using such preformed films in the material because they will increase costs from both the perspective of material procurement and the perspective of the lamination operation. Preformed films can have different mechanical properties and can range from biaxially oriented tough films obtained only by extrusion cast film to films made by film blowing and the inherent polymer orientation that occurs in the process or with additional subsequent orientation. However, it is preferred to use polymer materials that are only extrusion coated or extrusion laminated.

[0179] 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 is currently the type of polymer most commonly used for the innermost layer to achieve the best balance of liquid-tightness and heat-sealability and produce the best package integrity for heat-sealed packaging containers. By carefully selecting the ingredients of this layer, the amount of polymer in this layer can be optimized to be as low as possible while still producing a strong and reliable package filled with product.

[0180] In one embodiment, the second innermost liquid-tight, heat-sealable material layer may be or comprise a preformed polymer film comprising a heat-sealable thermoplastic polymer material and optionally another layer of material for providing improved robustness of the mechanical properties of the laminated packaging material.

[0181] In a specific embodiment, the laminated packaging material may have a preformed polymer film substrate laminated on the inner side of a paper substrate or a coated paper substrate, i.e., on the side of the paper substrate opposite to the side laminated to the bulk layer, wherein the preformed polymer film substrate has a vapor deposited coating of a gas barrier material selected from metals, metal oxides, inorganic oxides and amorphous diamond-like carbon coatings.

[0182] According to different specific embodiments, the laminated packaging material can have a preformed polymer film substrate laminated on the inner side of a paper substrate or the inner side of a coated paper substrate, i.e., on the side of the paper substrate opposite to the side laminated to the main layer, wherein the preformed polymer film is filled with an inorganic layered compound to provide gas and vapor barrier properties to the polymer film.

[0183] According to another specific embodiment, the laminated packaging material may have a prefabricated polymer film substrate laminated on the inner side of a paper substrate or a coated paper substrate, i.e. on one side of the paper substrate which is opposite to the side laminated to the main layer, wherein the prefabricated polymer film has been coated with a gas barrier material obtained by dispersing or dissolving a gas barrier material composition and subsequently dried to form a dry coating having a 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).

[0184] The purpose of any of the previously listed specific embodiments is to add complementary properties to the laminated packaging material when using only the paper substrate itself as a gas barrier material in a laminated structure, or when using such a coated paper substrate, or wherein the applied coating only provides some gas barrier properties, or when the coating only has a moisture-sensitive gas barrier material. By laminating the coated paper substrate to an additional polymer film, which adds some further moisture oxygen barrier properties, or at least water vapor barrier properties, at least two different gas barrier materials can interact to provide the overall laminated structure with further enhanced overall barrier properties. The necessary adhesive layer between the paper substrate and the additional barrier film ensures such enhanced barrier properties and can bring them to a synergistic level, because the intermediate adhesive layer acts as an additional "gas and vapor migration inhibitor" in the laminated structure.

[0185] The film may include a heat sealable layer, or may be fully heat sealable such that it forms or becomes part of an innermost heat sealable layer.

[0186] The outer and innermost liquid-tight layers, as well as the laminate layers within the laminate structure, do not generally add high barrier properties to migrating gas molecules or small molecules. Their purpose is to provide an immediate barrier to prevent water or other liquids from penetrating the cellulose-based bulk material and other paper layers. Liquid barrier layers can also prevent water vapor from migrating to the cellulose and making it wet, but they cannot maintain the moisture content of the laminate structure to zero or to the low levels of "dry" paper (about 7-8% at ambient temperature (i.e., 23 degrees Celsius and 50% relative humidity (RH)). The moisture content in the laminated carton material of liquid-filled packaging containers is generally quite high, and migration through the material will occur unless further water vapor barriers are included, such as aluminum foil, vapor deposited metallization layers, other vapor deposited coatings, layers of inorganic materials, or other polymeric materials.

[0187] In any of the previously listed embodiments involving preformed films, the preformed polymer film may comprise a polymer selected from any of polypropylene, polyethylene, blends thereof, and copolymers of ethylene and propylene and optionally additional comonomers. According to another embodiment, the preformed polymer film may comprise a polymer selected from high density polyethylene or linear low density polyethylene.

[0188] On the inside of the preformed film, there may be an additional extrusion coated layer or multilayer portion of an innermost heat sealable and liquid tight polymer as described in any of the above alternatives.Such a heat sealable thermoplastic polymer may also or alternatively form part of the preformed film.

[0189] The paper or paperboard main body layer used in the present invention generally has a thickness of about 100 μm to about 600 μm and a weight of about 100-500 g / m 2 , preferably about 200-300g / m 2 of surface weight and can be a conventional paper or paperboard with suitable packaging quality. The breaking strain of a conventional paper or paperboard body layer in MD is lower than 3% and is therefore not stretchable. The purpose of the body layer in the laminated packaging material of the present invention is to provide dimensional stability, rigidity and hardness to the packaging container, for example for use under humid conditions and / or for storing liquids and wet (heavy) foods. On the other hand, a thin and stretchable paper substrate with a breaking strain in the machine direction higher than 3% provides a good carrier layer for a thin and delicate gas barrier coating, thereby being able to improve the gas barrier properties of such packaging containers.

[0190] For low-cost aseptic, long-term packaging of liquid foods, thinner packaging laminates with thinner paper core layers can be used. Packaging containers made from such packaging laminates are not folded into shape, but more like pillow-shaped flexible bags. Suitable paper for such bag packaging typically has a g / m 2 , preferably about 70 to about 120 g / m 2 , more preferably 70 to about 110 g / m 2 surface weight.

[0191] The paper substrate may be bonded to the bulk layer via an intermediate adhesive or thermoplastic polymer bonding layer, thereby bonding the uncoated surface of the barrier coated paper to the bulk layer. According to one embodiment, the bonding layer is a polyolefin layer, such as, in particular, a polyethylene-based polyolefin copolymer or blend layer, which comprises mainly ethylene monomer units. The bonding layer may bond the bulk layer 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 being conveyed through the lamination roll nip, thereby providing a laminated structure by extrusion lamination.

[0192] In another embodiment, the barrier-coated cellulose-based substrate can be bonded to the main layer by wet-applying an aqueous dispersion of an adhesive composition comprising a viscous polymer adhesive to one of the coils to be laminated, and pressing them together as the two paper coils advance through the laminating roller gap, thereby providing a laminated structure by wet lamination. In the subsequent lamination process, the moisture of the aqueous adhesive composition is absorbed into the fibrous cellulose network of the two paper layers and partially evaporates over time. Therefore, a forced drying step is not required. The viscous polymer adhesive is selected from the group of polymers and copolymers comprising acrylic polymers and copolymers, starch, cellulose and polysaccharide derivatives, vinyl acetate and vinyl alcohol. In order to obtain optimal environmental and sustainability characteristics, adhesives from plants or non-fossil sources are preferred.

[0193] Suitable thermoplastics for the outermost and innermost liquid-tight layers are polyolefins, such as polyethylene and polypropylene homopolymers or copolymers, preferably polyethylene, more preferably selected from the group comprising low density polyethylene (LDPE), polyethylene of linear LDPE (LLDPE), single site catalyst metallocene polyethylene (m-LLDPE) and blends or copolymers thereof. According to one embodiment, the outermost liquid-tight layer is LDPE, while the innermost heat-sealable liquid-tight layer is a blended composition of m-LLDPE and LDPE to obtain optimal lamination and heat sealing properties.

[0194] The same thermoplastic polyolefin-based materials, particularly polyethylene, as listed for the outermost and innermost layers are also suitable for adhesive layers within the laminate, i.e. between bulk or core layers, such as paper or paperboard, and additional barrier films or sheets. In one embodiment, the thermoplastic adhesive layer can be a simpler or conventional polyethylene layer, such as a low density polyethylene (LDPE) layer.

[0195] Polyethylene-based polymers have been used and optimized in the field of liquid carton packaging materials for a long time, but other liquid-tight materials, such as thermoplastic polymer materials, for further providing heat sealability and heat processability, such as other polyolefins, such as other polyethylenes or polypropylenes, or such as polyesters, are also conceivable within the subject matter of the present invention. Therefore, within the subject matter of the present invention, all types of bio-based such thermoplastic materials are conceivable, as long as the separate gas barrier properties must still be provided by the described materials (stretchable paper substrate) in connection with the use of the present invention, as well as the stretchable paper substrate with a barrier coating.

[0196] In a further embodiment, the second innermost liquid-tight heat-sealable polyolefin layer is a prefabricated film comprising a polyolefin identical or similar to that described above, to improve the robustness of the mechanical properties of the packaging material. Due to the manufacturing process in blown film and film casting operations and optional subsequent film orientation operating steps, the polymer of this type of film has obtained the different performances that may be obtained with the polyolefin layer of (total) extrusion coating. Therefore, this prefabricated polymer film contributes to the mechanical robustness of laminated packaging materials and the mechanical strength and the packaging integrity of the packaging container formed and filled by the laminated packaging materials.

[0197] According to another embodiment, suitable adhesive or tie layers within the laminate, for example between the bulk or core layer and the barrier coated paper substrate, or between the innermost liquid-tight layer, the heat sealable layer and the paper substrate, may be so-called adhesive thermoplastic polymers, such as modified polyolefins based on LDPE or LLDPE copolymers or graft copolymers with monomer units containing functional groups, for example as carboxyl or glycidyl functional groups, such as (meth)acrylic acid monomers or maleic anhydride (MAH) monomers, (i.e. ethylene acrylic acid copolymers (EAA) or ethylene methacrylic acid copolymers (EMAA)), ethylene-glycidyl (meth)acrylate copolymers (EG(M)A) or MAH-grafted polyethylene (MAH-g-PE). Another example of such modified polymers or adhesive polymers are so-called ionomers or ionomeric polymers. Preferably, the modified polyolefin is an ethylene acrylic acid copolymer (EAA) or an ethylene methacrylic acid copolymer (EMAA).

[0198] The laminated packaging material produced according to the above method provides good integrity when converted into a filled packaging container, either by good adhesion between adjacent layers within the laminate structure and by providing a good quality barrier coating and barrier pre-coating, either by one or a combination of the above. In particular, for the packaging of liquids and wet foods, it is important to maintain interlayer adhesion within the laminated packaging material as well as oxygen barrier properties also under wet packaging conditions.

[0199] According to a further embodiment, a packaging container formed from a laminated packaging material may be partially sealed, filled with a liquid or semi-liquid food product, and subsequently sealed by sealing the packaging material to itself, optionally in combination with a plastic opening or top of the package.

[0200] In summary, a robust and reliable package for liquid food packaging, for long shelf life and storage, as defined in the present invention, can be obtained by using a paper substrate further coated with a barrier layer or laminated to an additional barrier material layer in a laminated package, due to the improved properties provided by the paper substrate itself. The laminated packaging material structure is more suitable for forming a folding and forming package, both because of the improved interaction and adhesion between the paper substrate and the gas barrier material coating, and because of the contribution of the paper substrate itself to any improvement in gas barrier properties, such as when the paper substrate is a stretchable paper substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0201] Preferred embodiments of the present invention will be described below with reference to the accompanying drawings, in which:

[0202] Figure 1a-1b schematically shows a cross section of an embodiment of a stretchable paper substrate for use according to the present invention,

[0203] Figure 1c-1e SEM images of the surface and cross section of the paper substrate of the present invention are shown,

[0204] Figure 2a-2b Schematically shows an alternative embodiment of a cross section of a stretchable paper substrate for use according to the invention,

[0205] Figure 3a-3c shows a schematic cross-sectional view of a gas barrier coated paper substrate according to the present invention,

[0206] Figure 4a-4b A laminated packaging material according to the present invention is shown, which comprises Figure 1a-1b and the barrier-coated paper substrate embodiments of 2a-2b,

[0207] Figure 5 Another embodiment of the laminated packaging material according to the present invention is shown, which comprises Figure 3c or the barrier-coated paper substrate of 1a or 1b,

[0208] Figure 6a A method for dispensing a base layer or barrier pre-coat composition onto a paper-based substrate is schematically shown.

[0209] Figure 6b Schematically showing a method for melt (co)extrusion coating of a thermoplastic heat-sealable and liquid-tight polymer onto a web substrate to form the innermost and outermost layers of the packaging laminate of the present invention,

[0210] Figure 7a A schematic diagram of an apparatus for physical vapor deposition (PVD) coating onto a paper substrate or film using a solid metal evaporator is shown,

[0211] Figure 7b A schematic diagram of an apparatus for plasma enhanced chemical vapor deposition (PECVD) coating on a paper substrate or film by magnetron plasma is shown,

[0212] Figure 8a , 8b 8c and 8d show typical examples of packaging containers produced from the laminated packaging material according to the present invention, and

[0213] Fig. 9 The principles of how such packaging containers can be manufactured from packaging laminate in a continuous, roll-fed, form, fill and seal process are shown. DETAILED DESCRIPTION Example Invention Example 1 Inventive Example 1A: Paper substrate production

[0214] Two types of pulp were provided: i) ECF bleached kraft pulp from softwood, namely a mixture of pine and spruce; ii) ECF bleached kraft pulp from hardwood, namely birch.

[0215] The softwood pulp is refined using a high-consistency (HC) refiner with a specific energy of 200 kWh / ton (net energy input per ton of dry fiber). The HC refined pulp is then mixed with waste paper pulp comprising a mixture of bleached softwood and hardwood pulp in a mixing chest (the majority of the waste paper comes from the same paper production). The share of waste paper in the softwood-based mixture is 10%. The softwood-based mixture is then refined by low-consistency (LC) refining with a specific energy of 80-85 kWh / ton. This LC refining results in a Schopper-Riegler (°SR) of about 26°SR according to ISO 5267-1:1999.

[0216] Hardwood pulp was mixed separately with waste paper of the same type and then refined by low consistency refining using a specific energy of 90 kWh / ton. The share of waste paper in the hardwood based mixture was 20%. The Schopper-Riegler (°SR) value obtained for the LC refined hardwood based mixture was about 44°SR.

[0217] Papermaking chemicals (4 kg / ton of cationic starch, 0.2 kg / ton of silica, 1.5 kg / ton of rosin size and 2.2 kg / ton of alum) were added to both fiber streams. The softwood-based mixture was pumped into a bottom ply head box of a double-layer Fourdrinier paper machine, while the hardwood-based mixture was pumped into the top head box of the same Fourdrinier paper machine. The dry mass flow through each head box was similar and adjusted to achieve a total grammage of 63 g / m before coating. 2 , divided into bottom layer (33g / m 2 ) and top layer (30g / m 2 ). The vertical slicing lip of the bottom headbox is 33 mm and that of the top headbox is 18.5 mm, which reflects the relatively low headbox consistency (about 0.14% for the bottom and 0.25% for the top). The wire speed is 608 m / min. In paper machines specially adapted for this product, the wire speed can be much higher.

[0218] The two layers of paper formed on the Fourdrinier paper machine were pressed together at about 10% dryness and further dewatered to about 20% dryness using vacuum foil boxes and then wet pressed in a press section with two single felt press nips, with the top side of the first press being felt and the bottom side of the second press being felt.

[0219] After wet pressing, the web is dried to about 65% dryness in the pre-drying section and then enters the stretchable unit. The stretchable unit (which is a double roller compactor type, commonly called an "Expanda") is operated with an entry web speed of about 638 m / min and an exit web speed of about 581 m / min. As a result, the paper web is compacted in the machine direction (the paper web becomes "shorter" by about 9%), thereby increasing the breaking strain value ("stretchability") of the final paper. The drive group after the stretchable unit runs at a slightly increased speed, resulting in a lower MD strain value at break. After the stretchable unit, the paper web is directly dried with conventional steam heated cylinders in the post-drying section to form a paper substrate with a moisture content of about 6%. Inventive Example 1B: Impregnation

[0220] The paper substrate in Inventive Example 1A was impregnated offline 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 included glyoxal (Cartabond TSI) in an amount of 6% by weight based on the content of PVOH. Glyoxal was used as a crosslinking agent. The viscosity of the composition was 74 mPa*s (measured at 60°C). The amount of PVOH applied was 1 g / m on the top side. 2 , 2g / m on the reverse / bottom side2 The reason for using a higher amount of PVOH on the reverse / bottom side is that the pulp used to form the bottom layer has a lower SR value (hence the reverse / bottom side has a lower surface density compared to the top side). The PVOH impregnated paper substrate was dried using hot air to a moisture content of about 8%. The properties of the dried PVOH impregnated paper substrate are listed in Table 1 below. Embodiment 1C of the present invention :Super calendering

[0221] The impregnated paper substrate in Inventive Example 1B was re-moistened to 15%. The re-moistened paper was fed into a pilot off-line multi-nip calender, also known as a super calender (number of nip zones was 12). Super calendering was performed on hot rolls using a surface temperature of 140°C, which can be obtained by an external induction heater to obtain a stretchable high density paper. The line load of each nip was 360 kN / m (simulating 400 kN / m in full-scale production) and the speed was 360 m / min (simulating 400 m / min in full-scale production). The total super calendering nip pulse was about 720 kPa·s [number of nip zones x line load / web speed]. The heating of the hot rolls dried the stretchable high density paper. The moisture content at the time of winding was about 5.5%. The properties of the stretchable high density paper are listed in Table 1 below. Comparative Example 1

[0222] This comparative example is not disclosed prior art, but is part of a co-pending patent application. Comparative Example 1A: Paper Substrate Production (2-ply Paper)

[0223] Two pulps were provided: i) ECF bleached kraft pulp from softwood, namely a mixture of pine and spruce; and ii) ECF bleached kraft pulp from hardwood, namely birch.

[0224] The softwood pulp was refined using a high consistency (HC) refiner at 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 waste paper pulp, which consisted of a mixture of bleached softwood pulp and hardwood pulp (most of the waste paper came from the same paper production). The breakage ratio in this softwood mixture was 30%. The softwood-based mixture was then refined by low consistency (LC) refining at a specific energy of 75 kWh / ton. This LC refining resulted in a Schopper-Riegler (°SR) of about 30°SR according to ISO 5267-1:1999.

[0225] Hardwood pulp was mixed with the same type of broke separately and then refined by low consistency refining using a specific energy of 85 kWh / ton. The breakage ratio in the hardwood mix was 20%. The Schhopper-Riegler (°SR) value of the LC refined hardwood based mix was about 38°SR.

[0226] Papermaking chemicals (4 kg / ton cationic starch, 0.2 kg / ton silica and 0.4 kg / ton AKD) were added to each of the two fiber streams. The softwood-based mixture was pumped to the bottom headbox of a two-layer Fourdrinier machine, while the hardwood-based mixture was pumped to the top headbox of the same Fourdrinier machine. The dry mass flow through each headbox was the same and was adjusted to achieve 60 g / m before coating. 2 Total weight (i.e. 30g / m 2 ). The vertical slice lip of the bottom headbox is 34 mm and that of the top headbox is 16 mm, which reflects the relatively low headbox consistency (about 0.12% for the bottom and 0.25% for the top). The line speed is 600 m / min. In paper machines specifically adapted for this product, the line speed can be quite high.

[0227] The two layers formed on the Fourdrinier wire machine were laid together at about 10% dryness and further dewatered to about 20% dryness using a vacuum foil box and then wet pressed in a press section with two single-felt press nips, with the felt of the first press on the top side and the felt of the second press on the bottom side.

[0228] After wet pressing, the paper web was dried in a conventional multi-drum dryer to form a paper substrate with a moisture content of about 5%. Prior to winding, the paper substrate was calendered in a soft nip at a line load of 20 kN / m. Comparative Example 1B: Impregnation

[0229] The paper substrate from 1A was impregnated offline from both sides with an aqueous polyvinyl alcohol (PVOH) composition in a conventional film press. The type of PVOH was Poval 10 / 98 from Kuraray, which was present in the composition at a concentration of 10% (in another test, at a concentration of 8%, which also provided good results). The composition further comprised glyoxal (Cartabond TSI) in an amount of 6 weight percent compared to the amount of PVOH. Glyoxal served as a crosslinking agent. The viscosity of the composition was 74 mPa*s (measured at 60°C). The coating amount of PVOH was 1 g / m on the top side. 2 , 2g / m on the reverse / bottom side 2The reason for using a higher amount of PVOH on the reverse side / bottom side is that the pulp used to form the bottom side has a lower SR value (therefore, the surface density of the reverse side / bottom side is lower compared to the top side). The PVOH-impregnated paper substrate is dried with hot air to a moisture content of 8%. Comparative Example 1C: Supercalendering

[0230] The impregnated paper substrate from 1B is rewetted to 15%. The rewetted paper is fed into an off-line multi-nip calender, also known as a supercalender (the number of nips is 12). Supercalendering is carried out at a surface temperature of 140 °C on the hot rolls, which can be obtained by an external induction heater, to obtain a high-density paper. The line load in each nip is 405 kN / m (simulating 450 kN / m in full-scale production). The total impulse of the supercalender nips is approximately 800 kPa·s [#nips × line load / coil speed]. The heating of the hot rolls dries the high-density paper. The moisture content at winding is 8%. The properties of the obtained high-density paper are listed in Table 1 below. Comparative Example 2: Paper substrate (single-layer paper)

[0231] This comparative example is not prior art that has been published, but is part of a co-pending patent application.

[0232] A single-layer paper is provided, which is used for different purposes, but is manufactured by a similar process and has properties similar to the papers of Invention Example 1 and Comparative Example 2. The single-layer paper is composed of kraft softwood pulp, kraft hardwood pulp, and a small amount of CTMP pulp mixed in a mixing ratio of 45:45:10. The single-layer paper is impregnated with polyvinyl alcohol from the top side and then calendered to a density of about 1050 kg / m 3 and the resulting grammage is 45 g / m 2 . The top side surface has a surface roughness of about 25 ml / min Bendtsen. Comparative Example 3: Paper substrate (single-layer paper)

[0233] A single-layer paper with a composition similar to the paper substrate of Comparative Example 2 is provided. The single-layer paper is impregnated with polyvinyl alcohol from the top side and calendered to a density of about 1100 kg / m 3 and the final grammage is 57 g / m 2 . The smoothness of the top side surface is less than 15 ml / min Bendtsen. Test 1: Final properties of paper substrate

[0234] The properties of the paper substrates used in Inventive Example 1 and Comparative Examples 1-3 are listed in Table 1 below. Table 1 also includes the paper properties of Nordic Paper's commercial oil-proof paper, which is used for similar purposes in liquid carton packaging in the prior art. Nordic Paper Super Perga WS paper of Comparative Example 4 is used as a gas barrier paper substrate in WO2017 / 089508.

[0235] For Table 1, the following applies: Grammage is measured according to ISO 536:2019 in g / m 2 . Thickness is measured according to ISO534:2011. Density is measured according to ISO 534:2011, unit is kg / m 3 . Roughness refers to the Bendtsen roughness, measured according to ISO 8791-2:2013, in ml / min. The strain at break is measured according to ISO 1924-3:2005 in the machine direction MD and / or cross direction CD. The tensile strength index is measured according to ISO 1924-3:2005 in MD and CD, in Nm / g. The Canadian Standard Freeness "CSF", a measure of the drainage of the fiber, is measured in ml according to ISO 5267-2:2001 after repulping according to the Valmet Repulping Method using a Valmet pulper type HD400. The Valmet Repulping Method is described in more detail below. °SR is measured according to ISO 5267-1:1999 after repulping according to ISO 5263-1:2004. Recyclability is measured according to PTS method PTS-RH 021 / 97. The recyclable fibers remaining after screening out the residues are reported. Oxygen transmission rate (OTR) is measured on the top side of the paper using a 20 g / m 2 Measured after LDPE lamination, unit is cm 3 / m 2 / 24h, 0.2atm (21%) oxygen. Table 1 §According to the supplier's data sheet ¤ Each side is impregnated with 1.5g / m 2 The test was conducted on high density paper of PVOH. *Weight: 38g / m 2 Instead of 32g / m 2 **Weight: 45g / m 2 , instead of 32g / m 2

[0236] The Valmet repulping process was carried out as described below. The paper was repulped using a Valmet pulper of the HD 400 type, which was used for stock preparation, i.e. fiber decomposition. Agitation was performed using an impeller with three radial serrated blades, the blade size being 30×40 mm, rotating at a speed of 3000 rpm. The paper was cut into pieces of 90x90 mm. 0.5 kg of air-dried paper pieces were mixed with 10 liters of water, i.e. a consistency of 5%, and repulped at a temperature of 57°C within 2.5 minutes. Then 5 liters of water were added, providing a consistency of 3.3%, and repulped at a temperature of 57°C for another 17.5 minutes. The total repulping time was therefore 20 minutes.

[0237] Determination of Canadian Standard Freeness of Pulp: The pulp obtained from the above-mentioned Valmet repulping process was diluted to about 0.3% and tested for Canadian Standard Freeness according to ISO5267-2:2001.

[0238] As shown in Table 1, the paper substrate used in Inventive Example 1 had very similar properties to the papers in Comparative Examples 1-3, except for the strain at break in the MD, which was higher due to compaction of the paper in the stretchable unit during the papermaking process. Test 2: Laminated Materials and Packaging Containers

[0239] The paper substrates of Comparative Examples 1 and 2 were further dispersion coated twice with intermediate and subsequent drying operations to provide 3 g / m 2 The PVOH coated paper substrate was further metallized to an optical density of about 2.

[0240] The gas barrier coated paper substrate is further coated with 20 g / m 2 The OTR values ​​of the coated papers of Comparative Examples 1 and 2 measured at 23°C and 80% relative humidity (RH) were not significantly higher than the OTR values ​​measured at 23°C and 50% RH (for the barrier-coated substrate of Comparative Example 1, the OTR at 23 / 50 and 23 / 80 was about 0.34 cm 3 / m 2 / 24h, 0.2atm. For Comparative Example 2, the OTRs under these two conditions were 0.25 and 0.27cm, respectively. 3 / m 2 / 24h, 0.2atm, i.e. only very small changes within the error range).

[0241] The paper substrate used in Inventive Example 1 was also dispersed coated twice with intermediate and subsequent drying operations to provide 3 g / m 2Continuous, uninterrupted PVOH coating. The PVOH coated paper substrate was further metallized to an optical density of about 2.2 and further coated with 20 g / m 2 LDPE, as described above. Also in this case, there was no significant increase in the OTR measured at 23°C and 80% RH compared to 23°C and 50% RH (OTR increased only from 0.31 to 0.34 cm 3 / m 2 / 24h, 0.2atm (21%) oxygen).

[0242] It is therefore concluded that the paper barrier material according to the present invention is no more sensitive to higher humidity conditions than similar recently developed paper barriers which have a lower conventional strain to break in the MD, ie are "non-stretchable".

[0243] Laminated packaging materials comprising the barrier-coated paper substrates according to Comparative Examples 1 and 2 and Inventive Example 1 were then produced according to the layer structure / LDPE12 g / m 2 / Paperboard 80mN / LDPE 15 or 20g / m 2 / paper substrate+PVOH+met / adhesive EAA copolymer 6g / m 2 +19 or 29g / m 2 Blend LDPE+mLLDPE /

[0244] Packaged in Tetra The products are produced in an E3 / CompactFlex filler. This type of filler is capable of filling portion packs at a rate of 9,000 packs / hour and has the flexibility to allow quick changeover between different packaging formats. format, with a capacity of 200 ml.

[0245] No major issues with package integrity (i.e., how well the package seals relative to the surrounding environment) and sealing performance were found during the trial and were therefore considered successful.

[0246] Oxygen transmission rate of flat packaging materials is measured using a coulometric detector according to standard ASTM F1927-14. The humidity level is 50% or 80% relative humidity. The unit is cm 3 / m 2 / 24h, with the option of using 0.2atm or 1atm oxygen pressure. In order to be able to compare the OTR value measured at 1atm with the OTR value measured at 0.2atm, multiply the previous value by 0.2.

[0247] The oxygen transmission rate of the package (filled, empty and dry) is measured at 0.2 atm (ambient air contains 21% oxygen) according to ASTM F1307-14. The unit is cm 3 / Packaging / 24h.

[0248] The package is mounted on a dedicated stand; the inside of the package is purged with nitrogen; the outside of the package is exposed to the environment surrounding the instrument. As oxygen permeates through the package into the nitrogen carrier gas, it is transported to the coulometric sensor. The sensor reads how much oxygen has leaked into the nitrogen inside the package.

[0249] Use 32g / m from Nordic Paper 2 Greaseproof PaperSuper WS Preparation Comparative Examples 4-1 and 4-2 (existing technologies and reference examples for laminated packaging materials). (Comparative Example 6 in Table 3 used 38 g / m 2 Super WS. )

[0250] The properties of the laminated packaging material are listed in Table 2 below. Table 2 * / LDPE 12g / m 2 / Paperboard 260mN / LDPE 20g / m 2 / paper substrate+PVOH+met / LDPE 20g / m 2 / LDPE+mLLDPE 20g / m 2 / ** / LDPE 12g / m 2 / Paperboard 80mN / LDPE 20g / m 2 / Paper substrate+PVOH+met / LDPE 40g / m 2 / *** / LDPE 12g / m 2 / Paperboard 80mN / LDPE 20g / m 2 / paper substrate+PVOH+met / adhesive EAA copolymer 6g / m 2 +29g / m 2 LDPE+mLLDPE blend / **** / LDPE 12g / m 2 / Paperboard 80mN / LDPE 15g / m 2 / paper substrate+PVOH+met / adhesive EAA copolymer 6g / m 2 +19g / m2 Mixture LDPE+mLLDPE /

[0251] Although there is a difference between the comparative examples and the examples according to the invention in the amount of thermoplastic polyethylene-based polymer in the layers facing the interior of the package, namely 40 or 35 g / m 2 and 25g / m 2 , but this has no practical effect on comparing oxygen transmission rates through flat, unfolded materials, as polyethylene is a poor oxygen barrier relative to paper substrates with applied impregnations and / or coatings. Typical oxygen transmission rates for LDPE at 40 μm thickness are 600-900 cm 3 / m 2 / 24h / 0.2atm(23℃). Furthermore, if thicker polyethylene layers are considered more beneficial for reducing OTR, these results show that there seems to be no such effect. The positive effect is primarily due to the gas barrier coated paper material, in this case to the paper substrate on which the barrier coating is applied.

[0252] As shown in Table 2, the paper substrate of the present invention (Inventive Example 1) not only provided the laminate with the lowest OTR measured after forming the package, but also provided the laminate with the lowest loss factor, indicating that the stability is further improved when formed into a packaging container. The low OTR value of a flat material is of less value in oxygen-sensitive packaging if the OTR value increases too much after folding and forming a filled three-dimensional package. Test 3: Recyclability Table 3 ¤ / LDPE 12g / m 2 / Paperboard 80mN / LDPE 20g / m 2 / Aluminum foil 6.3μm / Adhesive EAA copolymer 6g / m 2 +19g / m 2 LDPE+mLLDPE blend / ¤¤ / LDPE 12g / m2 / cardboard 80mN / LDPE 20g / m 2 / paper substrate+PVOH+met / adhesive EAA copolymer 6g / m 2 +19g / m 2 LDPE+mLLDPE blend /

[0253] The coarse waste, i.e., the non-fibrous recyclable part of the laminate, is polymers, aluminum foil, and some inseparable fibers, and is determined after repulping by a Valmet pulper. Repulping is carried out in the same manner as for determining the CSF value by repulping a single paper substrate in Example 1 above, except that the laminate packaging material to be repulped and analyzed is first cut into pieces of 30×90 mm. A plate with holes of 10 mm in diameter is used to sieve out the coarse waste, and then it is dried to 0% moisture content and calculated as the weight percentage of the dry (0% moisture) material introduced into the pulper.

[0254] The coarse waste determined by a global industrial supplier of equipment for fiber processing and recycling is prepared in a similar manner, but 20 g of the laminate is mixed into 2 l of water and decomposed to a concentration of about 1%, instead of 3.3%, for 18 minutes. The water temperature in this repulping test is also maintained at 57 °C.

[0255] As confirmed above, the paper substrates of the prior art for oxygen barrier coatings explored previously can generate a relatively high oxygen barrier level in the laminate packaging material and the packages filled and sealed therewith. However, it does not result in a reduction in the amount of waste materials in the existing recycling process, such as recycling used beverage cartons. As shown by comparing Comparative Example 6 with Comparative Example 5, although the use of aluminum foil as a raw material can be avoided, according to the tests of the above recycling company, the amount of materials (coarse waste) wasted or incinerated due to the recycling of the materials will be equally high.

[0256] The prior art paper-based barrier laminates have not been comparatively determined by a Valmet pulper and the above repulping method, but based on the results of Comparative Examples 6 and 5, it is expected that the Valmet method will also produce a similarly high proportion of coarse waste as the reference aluminum foil material tested. On the other hand, the laminates according to Comparative Examples 1 and 3 show a significantly reduced waste proportion, such as less than 20 weight percent of coarse waste. Compared with the laminate according to Comparative Example 3, the laminate containing the paper substrate of Example 1 as shown in Table 3 seems to require a slightly longer repulping time for the laminate, but in any case, at a longer repulping time, such as 50 minutes in this example, it also results in a lower proportion of coarse waste. The laminate tested for repulping in Comparative Example 3 contains a paper substrate with a composition similar to one of those in Comparative Example 2 but a higher grammage. It is expected that the laminate packaging material of Example 3B of Comparative Example 2 will produce a similarly low amount of coarse waste.

[0257] It is also expected that the laminated material comprising the barrier-coated, high density, stretchable paper substrate of Inventive Example 1 (as shown in Table 2) will have at least the same repulpability as Comparative Example 1 in Table 3, i.e., significantly improved recycling and repulping performance compared to the prior art reference materials (Comparative Examples 5 and 6 (and Comparative Examples 4-1 and 4-2)) because the high density paper substrate of Inventive Example 1 has very similar fiber content, composition and construction, and because the structure of the laminated material is the same. in conclusion

[0258] A 200 ml filled package made from the standard laminate of coated paper of Comparative Examples 1 and 2 of the co-pending and unpublished patent application typically exhibits a 200 ml fill rate of about 0.03 cm at 23°C, 50% RH. 3 / m 2 / day / 0.2atm. In addition, these values ​​do not seem to deteriorate significantly under 23°C, 80%RH environment. The OTR test is conducted 2-3 weeks after the production of the filled and sealed packages. The oxygen transmission rate of 0.03 in the 200ml package provides about 2-3 times better shelf life for oxygen sensitive products than the oxygen transmission rate of about 0.075 of Comparative Example 4-2 (i.e., prior art reference).

[0259] The oxygen transmission rate of the 200 ml package made from the laminate according to inventive example 1 is further improved to below 0.02, so that its shelf life is more than four times longer than that obtained from comparative example 4-2 (i.e., the prior art reference). The OTR of the laminates of comparative examples 1 and 2 of the present invention and of inventive example 1 (measured on a flat laminate) is at least as good as that of similar paper-based barrier laminates of the prior art.

[0260] Most importantly, however, recently developed and inventive materials do not exhibit the same degree of oxygen barrier performance loss when converting laminates into packaging containers that are filled, formed and heat sealed. However, this effect cannot be attributed to the higher amount of PVOH applied. The difference in PVOH coating weight may increase the oxygen barrier performance of flat laminates (unfolded), but this cannot explain the improved oxygen barrier properties that are also obtained in filled and sealed packages beyond the slight improvement level.

[0261] Generally, it has been demonstrated that the packaging integrity is good using the paper-based barriers of Comparative Examples 1 and 2 and of Example 1 according to the invention. In addition, it can be seen that when the paper-based grammage is low, for example, between 30 and 65 g / m 2 For example, between 35 and 60 g / m 2 For example, between 35 and 55 g / m 2For example, between 35 and 50 g / m 2 When the coated, non-stretchable paper substrate is thinner, the package integrity is improved. Therefore, the thickness of the paper substrate should preferably be 30 to 60 μm, such as 30 to 55 μm, such as 30 to 50 μm, such as 30 to 45 μm. If the coated, non-stretchable paper substrate is thicker, more polymer is required in the thermoplastic heat-sealable layer in order to form a tight and durable seal when the laminate is converted into a filled and sealed cuboid package. Therefore, a thinner paper substrate can reduce the proportion of thermoplastic polymer required in the overall packaging laminate, which is very important because packaging materials will need to adapt to recycling streams with extremely high fiber content in the future so that these materials can be recycled and reused instead of becoming waste.

[0262] Stretchable paper substrates also show this effect, and it is expected that overall thinner, more stretchable paper substrates will provide even better results, allowing the thermoplastic heat-sealable polymer content in laminated packaging materials to be further reduced.

[0263] In addition, the impregnated high density paper substrates of Comparative Examples 1 and 2 provide improved recycling and repulping properties for the laminates compared to aluminum foil based packaging materials and non-aluminum foil gas barrier based laminated packaging materials. Since the construction and cellulose content of the paper itself are very similar, the recycling and repulping properties of the high density stretchable paper of Example 1 of the present invention are expected to reach similar good levels. The operation of making the paper substrate more stretchable (i.e., stretchable, i.e., having a high breaking strain in the machine direction (MD)) by, for example, an Expanda stretchable unit is not expected to change the repulping properties. This improvement further supports the overall development of more sustainable packaging materials. It also enables the preservation of higher fiber content in laminated packaging materials used for packaging products that are very sensitive to oxygen, such as juices and other fruit or vegetable foods containing natural vitamin C. BRIEF DESCRIPTION OF THE DRAWINGS

[0264] Figure 1a In FIG. 1 , an embodiment of the paper substrate 10a of the present invention is shown in cross-section. The paper substrate 10a is primarily made of kraft cellulose fibers that are moderately refined to obtain good paper recycling properties. It also has a machine direction stretchability of at least 3%. In a film pressing operation in a papermaking process, 11a is impregnated with polyvinyl alcohol having a high degree of hydrolysis. The dry weight of the PVOH impregnated from the top side is about 1-1.5 g / m 2 The paper substrate can be coated with a total of about 2-4 g / m 2 The film is impregnated with PVOH and / or starch (e.g., a combination of PVOH on the top side and starch on the back side).

[0265] Figure 1bA cross-sectional view of a high density, stretchable paper substrate 10b of the present invention is shown, which is obtained by a method in which: Figure 1a The impregnated paper substrate 10a has been supercalendered at high pressure and temperature to obtain a thinner, denser, stretchable paper substrate.

[0266] Figure 1c An SEM image of a surface portion of a preferred paper substrate of the present invention is shown, which has been formed, wet pressed, dried, compacted, further dried, impregnated with PVOH, supercalendered, and then coated with about 3 g / m 2 Continuous gas barrier coating of PVOH,

[0267] Figure 1d An SEM image of a surface portion of the same preferred, compacted, PVOH impregnated and supercalendered paper substrate but not further coated with a gas barrier is shown. Figure 1d As shown, the PVOH in the impregnation did not form a film or continuous coating on the surface portion. The impregnated PVOH had penetrated into the fiber web. The impregnated paper substrate used in Comparative Example 1 showed a similar surface, that is, it was not seen that the PVOH formed a film or continuous coating on the surface portion of the paper.

[0268] Figure 1e An SEM image of a cross section 10e of the non-stretchable high density paper substrate used in Comparative Example 1 is shown. The dark grey area 15 is PVOH and the light grey area 16 is fiber. There are also unfilled pores 17. Therefore, the high density comparative paper is not filled with PVOH. However, Figure 1e This indicates that PVOH exists in the fiber web. From the images of the paper surface taken, it can be seen that most of the PVOH exists in the fiber body of the paper. Only a small part of the PVOH exists on the surface of the paper. Figure 1c and 1d From the results of the present invention, it seems that this is also the case for similar but compressed stretchable papers made from similar cellulose fibers and similar processes. As shown above, the compressed gas barrier coated paper of the present invention produced in a very similar manner can lead to further improved gas barrier properties of folding and forming packaging containers compared to Comparative Example 1.

[0269] exist Figure 2a The cross-section of the Figure 1a An embodiment of a stretchable paper substrate 20a similar to that shown in FIG. Figure 1a and Figure 1b The same compressed paper web made in is dewatered, wet pressed and dried to form a stretchable paper substrate without further impregnation with a polymer in a size press step.

[0270] Figure 2bAn embodiment of a high density stretchable paper substrate 20b is shown in cross section and is obtained by a process in which: Figure 2a The stretchable paper substrate 20a has been further supercalendered under high pressure and temperature to obtain a thinner and denser stretchable paper substrate.

[0271] exist Figure 3a , an embodiment of a gas barrier coated stretchable paper substrate 30a of the present invention is shown in cross section. Figure 1a Or preferably taken from Figure 1b The stretchable paper substrate 31a (the layer thickness ratios in Figures 1-5 do not reflect the actual thickness and the relative thickness ratio) and 31b are first coated with an aqueous gas barrier composition comprising PVOH in two coating steps, with intermediate and subsequent drying steps, so that the total dry weight of the applied layer 33a is twice 1.5 g / m 2 , i.e. 3g / m 2 .

[0272] The PVOH coated stretchable paper substrate 30a (i.e. including 31a and 33a) thus also has an aluminum metallized vapor deposited coating 34a on top of the PVOH coating 33a. The combination of this barrier coating structure with the stretchable paper substrate provides a gas barrier laminate material portion, thereby realizing a non-foil laminated packaging material (i.e., a laminated packaging material without traditional micron-thick (5-10 μm) aluminum foil or other metal foil) and providing high and durable gas barrier properties in a folded, formed, filled and heat-sealed packaging container made of this non-foil packaging material.

[0273] Figure 3b Another embodiment of the gas barrier coated stretchable paper substrate 30b of the present invention is shown, wherein the Figure 2a Instead of having an impregnated polymer inside the fibers of the paper substrate, the paper substrate is pre-coated with a base coating 32b comprising a polymer composition to impart a higher smoothness and / or surface quality to the multi-layer paper substrate barrier structure. The gas barrier coating 33b of PVOH and the subsequent metallization coating 34b are preferably coated with a base coating 32b of PVOH to provide a higher smoothness and / or surface quality to the multi-layer paper substrate barrier structure. Figure 3a The base coating 32b is applied in the same manner and in the same amount as in the above. The base coating forms a "bridge" for the stretchable paper substrate. A similar degree of improved performance can be obtained as with the impregnated gas barrier coated paper substrate 30a.

[0274] Figure 3c Another embodiment of the gas barrier coated stretchable paper substrate 30c of the present invention is shown, which corresponds to Figure 3a or Figure 3bPVOH coated paper substrate prior to final vapor deposition metallized coating in (base or pre-coat 32c is optional). This is another variation of a paper-based gas barrier material that can be combined with and laminated to another complementary barrier material in a laminated packaging material, such as a polymer film with a vapor deposited barrier coating applied. This laminated packaging material will also provide better and more durable non-foil gas barrier performance in fold-form, fill and heat seal packaging containers due to the increased high stretchability of the paper substrate 31c in the machine direction.

[0275] exist Figure 4a , a laminated packaging material 40a for liquid carton packaging is shown, wherein the laminated material comprises a cardboard body layer 41 of cardboard having a bending force of 80 mN and a strength of about 200 g / m 2 The packaging material is a laminate of the invention and also includes a liquid-tight and heat-sealable outer layer 42 of polyolefin applied on the outer side of the main layer 41, which side will point to the outside of the packaging container produced from the packaging laminate. The layer 42 is transparent to show the printed decorative pattern 47 applied to the main layer of paper or paperboard to the outside, thereby informing the contents of the package, the packaging brand and other information for consumers in retail facilities and food stores. The polyolefin of the outer layer 42 is a conventional low-density polyethylene (LDPE) of heat-sealable quality, but may also include other similar polymers, including LLDPE. The application amount is about 12g / m 2 . The innermost liquid-tight and heat-sealable layer 43 is arranged on the opposite side of the main body layer 41, which layer will be directed toward the interior of the packaging container produced from the packaging laminate material, that is, the layer 43 will be in direct contact with the packaged product. Therefore, the innermost heat-sealing layer 43 that forms a strong transverse heat seal of the liquid packaging container made of the laminated packaging material comprises a combination of one or more polyethylenes selected from the group consisting of LDPE, linear low-density polyethylene (LLDPE), and LLDPE produced by polymerizing ethylene monomers with C4-C8, more preferably C6-C8, α-olefin alkylene monomers in the presence of a metallocene catalyst, i.e., the so-called metallocene-LLDPE (m-LLDPE). Its application amount is about 19 g / m 2 .

[0276] The main body layer 41 is laminated to the Figure 3a The uncoated side of the barrier coated paper substrate 30a, i.e. 45a, is formed by melt extruding it as a thin polymer melt curtain between two paper webs, and thus laminating the main body layer and the barrier coated paper substrate to each other when all three layers pass through the cooling press nip. The thickness of the intermediate adhesive layer 46 is 12 to 22 μm, for example 12 to 18 μm.

[0277] The innermost heat sealable layer 43 may be composed of one or optionally two or more partial layers of the same or different kinds of LDPE or LLDPE or mixtures thereof and is well adhered to the metallized barrier deposited coating surface 34a of the barrier coated paper substrate 45a, i.e. 30a, by an intermediate coextrusion bonding or adhesive polymer layer 48, e.g., ethylene acrylic acid copolymer (EAA), thereby coating the barrier coated paper substrate 45a, i.e., 30a, with 5 to 7 g / m2 of the barrier coated paper substrate 45a, i.e., 30a, in a single melt coextrusion coating step. 2 The adhesive layer 48 and the innermost layer 43 are applied together to bond the innermost heat seal layer 43 to the barrier coated paper substrate 30a.

[0278] Alternatively, the main body layer 41 may be laminated to the substrate by wet lamination with an intermediate adhesive layer 46b of an adhesive polymer thin layer. Figure 3a On the barrier coated paper substrate described in , the intermediate adhesive layer 46b is obtained by applying an aqueous dispersion of, for example, PVOH, starch or polyvinyl acetate adhesive to one of the surfaces to be bonded to each other and then pressing them together in a roller nip. Due to the relatively thick absorbent bulk layer of the cellulose structure, this lamination step can be carried out at industrial speeds in an efficient cold lamination or ambient lamination step without the need for energy-consuming drying operations that are usually required to accelerate the evaporation of water. The dry coating amount of the intermediate adhesive layer 46b is only a few g / m 2 , for example 2 to 6 g / m 2 , thus eliminating the need for drying and evaporation.

[0279] Thus, compared to conventional melt extrusion lamination adhesive layers of polyethylene 46, the amount of thermoplastic polymer in the lamination layer can be significantly reduced.

[0280] Figure 4b In an alternative embodiment, Figure 3b The gas barrier coated paper substrate 30b shown in FIG. Figure 4a The same laminate structure as the gas barrier coated structure 45b is laminated in the same manner as the gas barrier coated paper substrate 30a.

[0281] Figure 5 Another embodiment of a different laminated packaging material 50 of the present invention for liquid carton packaging is shown in FIG. 1 , wherein the laminated material comprises a paperboard core layer 51 having a bending force of 80 mN and a strength of about 200 g / m 2 The packaging laminate has a grammage of 12 g / m2 and further comprises a polyolefin outer liquid-tight and heat-sealable layer 52 applied on the outer side of the main body layer 51, which side will point to the outside of the packaging container produced from the packaging laminate. The polyolefin of the outer layer 52 is a conventional low-density polyethylene (LDPE) with heat-sealable qualities and has been coated at 12 g / m2. 2 The amount is applied, but may include further similar polymers, including LLDPE.

[0282] The innermost liquid-tight and heat-sealable layer 53 is arranged on the opposite side of the main body layer 51, which layer 53 will face the interior of the packaging container produced from the packaging laminate, that is, the layer 53 will be in direct contact with the packaged product. Therefore, the innermost heat-seal layer 53 that forms a strong heat seal of the liquid packaging container made of the laminated packaging material comprises a combination of one or more polyethylenes selected from the group comprising LDPE, linear low-density polyethylene (LLDPE) and LLDPE produced by polymerizing ethylene monomers with C4-C8, more preferably C6-C8 α-olefin alkylene monomers in the presence of a metallocene catalyst, i.e., the so-called metallocene-LLDPE (m-LLDPE).

[0283] Figure 3c The barrier coated paper substrate 30c is further laminated to a complementary barrier film 54 by melt extrusion lamination with an intermediate adhesive layer 59 of low density polyethylene (LDPE), the complementary barrier film 54 comprising a polymer film substrate 54a, which is a biaxially oriented polypropylene (BOPP) film and is coated with a vapor deposited barrier coating 54b, which is an aluminum metallized coating. With this laminate, a moisture sensitive gas barrier coating (e.g., a PVOH coating) can be protected by a further metallized coating of the metallized polymer film, which is located on the inner side of the laminate, i.e., the side close to the liquid or wet food filling.

[0284] The main body layer 51 is then laminated to the substrate by wet lamination with an intermediate adhesive layer 56 of a thin layer of adhesive polymer. Figure 3c The uncoated, unlaminated side of the barrier-coated paper substrate 30c in the embodiment of the present invention is obtained by applying an aqueous dispersion of a PVOH or polyvinyl acetate adhesive to one of the surfaces to be bonded to each other and subsequently pressing them together in a roll nip. Thus, this lamination step can also be carried out with only a few g / m 2 The intermediate adhesive layer 56 is as follows Figure 4b The efficient cold or ambient lamination steps described are performed such that drying and evaporation are not required.

[0285] Therefore, if Figure 4a As described in , in the laminated packaging material, the amount of thermoplastic polymer in the lamination layer can still be reduced compared to conventional polyethylene melt extrusion lamination adhesive layers.

[0286] The innermost layer 53 is applied to the barrier coated film 54, optionally together with an adjacent adhesive polymer layer 58, in a coextrusion coating operation.

[0287] According to a further embodiment not shown, instead of the paper substrate 30c being coated with a gas barrier, Figure 1aor 1b of an uncoated paper substrate 10a or 10b, or Figure 2a The paper substrate 20a or 20b of 20a or 20b may be laminated into the same laminate structure as described above as the barrier structure 45.

[0288] The paper substrate having increased breaking strain in the machine direction adds flexibility to the laminated packaging material, which supports and relieves the various gas barrier coatings and layers in the laminate when folded and formed into a cubic packaging container for liquid carton packaging.

[0289] exist Figure 6a In the figure, an aqueous dispersion coating process 60a is shown, which can be used to apply a gas barrier coating 12 from an aqueous gas barrier composition to a substrate, or to wet-laminate two webs together through an aqueous adhesive composition, at least one of which has a fibrous cellulose surface. A paper substrate web 61a (e.g., paper substrate 11a; 11b in Figure 1, or paper substrate 21a; 21b in Figure 2) is conveyed to a dispersion coating station 62a, where an aqueous dispersion composition is applied to the top surface of the substrate by a roller. The water content of the aqueous composition is 80-99 weight percent, and there will be a large amount of water on the wet coated substrate, which needs to be heated, dried and evaporated to form a continuous uniform coating and have uniform quality in terms of barrier properties and surface properties (i.e., uniformity and wettability). Drying is performed by a hot air dryer 63a, which also allows water to evaporate and be removed from the surface of the paper substrate. As the substrate passes through the dryer, its temperature is kept constant at a temperature of 60 to 80°C. Alternatively, drying may be partially assisted by radiant heat from infrared lamps combined with hot air convection drying.

[0290] The resulting barrier coated paper substrate web 64a is conveyed to be cooled and wound onto a reel for intermediate storage, and subsequently the barrier deposited coating is further vapor-deposited onto the paper substrate 64a.

[0291] Figure 6b 3 shows the production of a laminated packaging material (e.g., FIG. 4 and FIG. 5 ) after first laminating the bulk layers 41, 51 to the barrier coated paper substrate of FIG. Figure 5 A process (60b) of a final lamination step of the laminated packaging material 40a, 40b or 50).

[0292] The body ply paperboard may be laminated to the barrier coated paper substrate by wet cold dispersion adhesive lamination or by melt extrusion lamination.

[0293] The resulting paper pre-laminated web 61b is fed from an intermediate storage reel, or directly from a laminating station for laminating pre-laminated paper. The non-laminated side of the bulk layer 41;51, i.e. its printed side, is engaged at a cooling nip 63 with a molten polymer curtain 62 of LDPE, which forms the outermost layer 42;52 of the laminate, which is extruded from an extruder feedhead and die 62b. Subsequently, the paper pre-laminated web, now having the outermost layer 62;42;52 coated on its printed side (i.e. the outer side), passes through a second extruder feedhead and die 64b and a lamination nip 65, where a molten polymer curtain 64 is engaged and coated onto the other side of the pre-laminate, i.e. the barrier coating side of the paper substrate. Thus, the innermost heat sealable layer 64:43;53 is co-extrusion coated onto the inner side of the paper pre-laminated web to form a finished laminated packaging material 66, which is ultimately wound onto a storage reel (not shown).

[0294] The two coextrusion steps at the lamination roll nips 63 and 65 may alternatively be performed as two consecutive steps in reverse order.

[0295] According to another embodiment, one or both of the outermost layers may alternatively be applied in a pre-lamination station, as described above, where the coextrusion coating layer is first applied to the outside of the (printed) body paperboard layer or to the barrier coated paper substrate and then the two pre-laminated paper webs may be joined to each other.

[0296] Figure 7a Schematic diagram of an embodiment of a physical vapor deposition (PVD) apparatus 70 for applying a metal coating, such as aluminum, to a coil of the present invention. A coated or uncoated paper substrate 71 is subjected to a continuous evaporative deposition 72 of evaporated aluminum on its pre-coated face to form a metallized layer of aluminum, or alternatively a mixture of oxygen and aluminum vapor is used to form an aluminum oxide deposition coating. The coating has a thickness of 5 to 200 nm, such as 5 to 100 nm, such as 10 to 50 nm, thereby forming a barrier-coated paper substrate 73 of the present invention. The aluminum vapor is formed by ion bombardment of an evaporation source of solid aluminum flakes at 72. For the coating of aluminum oxide, some oxygen can also be injected into the plasma chamber via the inlet port.

[0297] Figure 7bSchematic diagram of an embodiment of an apparatus 70b for plasma enhanced chemical vapor deposition coating PECVD, for example, for coating a hydrogenated amorphous diamond-like carbon coating onto a web substrate of the present invention. A web substrate 74a is subjected to continuous PECVD of a plasma on one of its surfaces in a plasma reaction zone 75, which is formed in the space between a magnetron electrode 76 and a cooled web conveyor drum 77, which also serves as an electrode, while the film is advanced forward by a rotating drum, passing through the plasma reaction zone along the circumferential surface of the drum. The plasma for depositing the amorphous DLC coating can be generated, for example, by injecting a gas precursor composition containing an organic hydrocarbon gas, such as acetylene or methane, into the plasma reaction chamber. Other gas barrier coatings, such as silicon oxide coatings, SiOx, can be applied by the same main PECVD method, then starting with a precursor gas of an organic silicon compound. The PECVD plasma chamber is maintained under vacuum conditions by continuously evacuating the chamber at outlets 78a and 78b.

[0298] Figure 8a An embodiment of a packaging container 50a produced by a packaging laminate according to the present invention is shown. The packaging container is particularly suitable for beverages, sauces, soups, etc. Typically, such a package has a volume of about 100 to 1000 ml. It can be any configuration, but preferably brick-shaped, with longitudinal seals 81a and transverse seals 82a, respectively, and optionally with an opening device 83. In another embodiment not shown, the packaging container can be shaped as a wedge. In order to obtain this "wedge", only the bottom portion of the package is folded so that the transverse heat seal at the bottom is hidden under the triangular corner fins, which are folded and sealed to the bottom of the package. The top transverse seal remains in an expanded state. In this way, the packaging container, which is only partially folded, is still easy to handle and is stable enough in size to be placed on a shelf in a food store or on any flat surface.

[0299] Figure 8b An alternative embodiment of a packaging container 80b produced from an alternative packaging laminate according to the present invention is shown. The alternative packaging laminate is thinner due to having a thinner paper body layer, so its dimensions are not stable enough to form a parallelepiped or wedge-shaped packaging container and is not folded after the transverse seal 82b. The packaging container will still be a pillow-shaped bag-like container and will be distributed and sold in this form.

[0300] Figure 8c A gable top package 50c is shown formed from a pre-cut sheet or blank, folded from a laminated packaging material comprising a paperboard bulk layer and the barrier coated paper substrate of the present invention. Flat top packages may also be formed from similar material blanks.

[0301] Figure 8dA bottle-like package 50d is shown which is a combination of a sleeve 54 formed from a pre-cut blank of the laminated packaging material of the present invention and a top 55 formed by injection molding plastic in combination with an opening device such as a screw plug. This type of package is sold for example under the trade name Tetra and Tetra These particular packages are formed by attaching a molded top 55 with an opening device attached in a closed position to a tubular sleeve 54 of laminated packaging material, sterilizing the bottle-top capsule so formed, filling it with the food product, and finally folding-forming the package bottom and sealing it.

[0302] Fig. 9 The principle described in the introduction of the present application is shown, i.e. a web of packaging material is formed into a tube 91 by overlapping the longitudinal edges 92a, 92b of the web and heat-sealing them to each other, thereby forming a lap joint 93. The tube is continuously filled 94 with the liquid food to be filled and divided into individual, filled packages by repeated double transverse seals 95 of the tube at a predetermined distance from each other below the level of the filler in the tube. The packages 96 are separated by cutting between the double transverse seals (top and bottom seals) and finally formed into the desired geometric configuration by forming folds along prepared crease lines in the material.

[0303] As a final note, the invention is not limited to the embodiments shown and described above but may vary within the scope of the claims.

Claims

1. Use of a paper substrate (10a; 10b; 20a; 20b) as a gas barrier material in a laminated packaging material for packaging oxygen-sensitive foods, such as liquid, semi-liquid or viscous foods or water, in, The paper substrate has a thickness of 30 g / m2 as measured according to ISO 536:2012. 2 Up to 100g / m 2 The polyester has a grammage of 0.1 wt. % and a machine direction strain at break of higher than 3 % as measured according to ISO 1924-3:2005 and a Bendtsen surface roughness on at least one side of lower than 150 ml / min as measured according to ISO 8791-2:2013.

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

3. The use according to any one of claims 1 and 2, in, The paper substrate has a strain at break in the cross direction higher than 5.0% measured according to ISO 1924-3:2005.

4. The use according to any one of claims 1 and 2, in, The paper substrate has a thickness of less than 90 g / m2 measured according to ISO 536:2012 2 , for example, less than 80g / m 2 , for example, less than 70g / m 2 , for example, less than 66g / m 2 , for example, less than 60g / m 2 , for example, less than 55g / m 2 , for example, less than 50g / m 2 The base weight.

5. Use according to any of the preceding claims, wherein the Bendtsen surface roughness on at least one side is below 100 ml / min, such as below 70 ml / min.

6. Use according to any of the preceding claims, wherein the paper substrate is impregnated with a polymer, for example selected from the group consisting of polyvinyl alcohol, PVOH, ethylene vinyl alcohol, EVOH, starch, starch derivatives, carboxymethylcellulose, CMC or other cellulose ethers.

7. Use according to any one of the preceding claims, wherein the paper substrate has a base coating comprising a polymer applied on the top side of the paper substrate.

8. The use according to any one of the preceding claims, in, The density of the paper substrate is at least 800 kg / m 3 , for example at least 900 kg / m 3 , for example at least 1000 kg / m 3 .

9. Use according to any one of the preceding claims, wherein the paper substrate has been calendered, such as supercalendered.

10. Use according to any one of the preceding claims, wherein cellulose fibres comprise at least 90% of the dry weight of the paper.

11. Use according to any one of the preceding claims, wherein the paper substrate is kraft paper.

12. 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, the paper substrate being as defined in any one of the use claims 1 to 11, wherein the paper substrate has at least one gas barrier coating (33a, 34a; 33b, 34b; 33c) of at least one gas barrier material, with a total coating thickness of 2 nm to 5000 nm, such as 2 nm to 4000 nm.

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

14. The gas barrier coated paper substrate according to any one of claims 12 and 13, wherein 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, nanofiber cellulose / microfiber cellulose, NFC / MFC, nanocrystalline cellulose, NCC and a mixture of two or more thereof.

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

16. A gas barrier coated paper substrate according to any one of claims 12 to 15, in, The paper substrate has a first gas barrier coating (33a; 33b) formed by coating a dispersion or solution of an aqueous composition of a gas barrier material and then drying it, and also 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.

17. A laminated packaging material (40a; 40b; 50) for oxygen-sensitive foods, the laminated packaging material (40a; 40b; 50) being for example used for packaging liquid, semi-liquid or viscous foods or water, and comprising a paper substrate (10a; 10b; 20a; 20b) as defined in any one of use claims 1 to 11 or a paper substrate (30a; 30b; 30c) coated with a gas barrier according to any one of claims 12 to 16, the laminated packaging material further comprising a first outermost liquid-tight material layer (42; 52) and a second innermost liquid-tight material layer (43; 53), and a main body layer (41; 51) of paper or paperboard or other cellulose-based material, and having the paper substrate (10a; 10b; 20a; 20b) or the gas-barrier-coated paper substrate (30a; 30b; 30c) laminated between the main body layer and the second innermost liquid-tight material layer.

18. The laminated packaging material according to claim 17, wherein by applying 0.5 g / m 2 Up to 10g / m 2 , for example 1g / m 2 Up to 5g / m 2 The paper substrate or the gas barrier coated paper substrate is laminated to the main layer by applying and drying an aqueous intermediate adhesive composition (46b; 56), wherein the aqueous intermediate adhesive composition comprises a water-dispersible adhesive 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.

19. The laminated packaging material according to any one of claims 17-18, having a pre-made polymer film laminated on the inner side of the paper substrate or the gas barrier coated paper substrate to improve the robustness of the mechanical properties of the laminated packaging material.

20. A laminated packaging material (50) according to any one of claims 17 to 19, comprising a preformed polymer film (54, 54a) laminated on the inner side 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 main layer, wherein the preformed 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.

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 laminated packaging material (40a; 40b; 50) as defined in any one of claims 17 to 20.

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