Cellulose-based substrate coated with a barrier layer, laminated packaging material and packaging container comprising a cellulose-based substrate

Abstract

The present invention relates to a cellulose-based substrate (10; 25a; 25b) coated with a barrier layer, and to a method of manufacturing such a cellulose-based substrate by dispersion coating a barrier pre-coat layer (13) and subsequently vapour deposition coating a barrier deposition coat layer (14). The present invention further relates to a laminated packaging material (20a; 20b) comprising a cellulose-based substrate (10) coated with a barrier layer, in particular for liquid carton food packaging, and to a liquid carton packaging container comprising the laminated packaging material.

Description

Technical Field

[0001] This invention relates to paper or cellulose-based substrates coated with a barrier layer, and a method for manufacturing the substrate by dispersively coating a barrier pre-coating and subsequently vapor-depositing a barrier deposition coating. The invention further relates to laminated packaging materials comprising such a paper or cellulose-based substrate coated with a barrier layer, particularly for liquid carton food packaging, and to such liquid carton packaging containers comprising the laminated packaging material. Background Technology

[0002] Single-use packaging containers for liquid foods are typically made of cardboard or thick cardboard-based packaging laminates. One common type of such packaging container is the Tetra Brik. These are trademarks sold primarily for the aseptic packaging of liquid foods (such as milk, juice, etc.) intended for long-term environmental storage. The packaging material in such known containers is typically a laminate comprising a main or core layer of paper, cardboard, or other cellulose-based material, and an outer liquid-tight layer of thermoplastic. To ensure the container is airtight, particularly oxygen-tight, for example for aseptic packaging and packaging milk or juice, the laminate in these containers typically includes at least one additional layer, most commonly aluminum foil.

[0003] On the inner side of the laminate, i.e., on the side facing the food contents to be filled into the container produced from the laminate, there is an innermost layer applied to the aluminum foil. This innermost layer may consist of one or more partial layers containing a heat-sealable thermoplastic polymer, such as an adhesive polymer and / or a polyolefin. Similarly, on the outer side of the body layer, there is an outermost heat-sealable polymer layer.

[0004] Packaging containers are typically produced using modern high-speed packaging machines. These machines form packages from packaging material rolls or preforms, fill them, and seal them. Therefore, packaging containers can be produced by transforming a laminated packaging material roll into a tube by welding the innermost and outermost heat-sealable thermoplastic polymer layers together, such that the two longitudinal edges of the roll are joined together at an overlapping joint. This tube is filled with the desired liquid food, and then the tube is separated into individual packages by repeating transverse seals below the level of the contents and spaced a predetermined distance apart. The packages are separated from the tube by cuts along the transverse seals, and the desired geometry, typically a parallelepiped, is obtained by folding along pre-prepared creases in the packaging material.

[0005] The main advantage of this continuous tube forming, filling, and sealing packaging method is that the roll material can be continuously sterilized before tube formation, thus providing the possibility of aseptic packaging methods. This method involves reducing bacteria in the liquid contents to be filled and the packaging material itself, and the filled packaging containers are produced under clean conditions, allowing the filled packaging to be stored for extended periods even at ambient temperatures without the risk of microbial growth in the filled product. As mentioned above, Tetra... Another important advantage of this type of packaging method is the possibility of continuous high-speed packaging, which has a significant impact on cost efficiency.

[0006] Packaging containers for sensitive liquid foods (such as milk or juice) can also be made from sheet preforms or preforms of the laminated packaging material of the present invention. Packaging is produced using a tubular preform of packaging laminate folded into a flat surface, by first standing the preform upright to form an open tubular container capsule, one open end of which is closed by folding and heat-sealing an integral end panel. The sealed container capsule is then filled with the food in question (e.g., juice) through its open end, which is then closed by further folding and heat-sealing a corresponding integral end panel. Examples of packaging containers made from sheet and tubular preforms are the conventional so-called mountain-top packaging. Packaging of this type, with a molded top and / or screw cap made of plastic, also exists.

[0007] The aluminum foil layer in packaging laminates provides gas barrier performance far superior to most other gas barrier materials. Traditional aluminum foil-based packaging laminates for aseptic packaging of liquid foods remain the most cost-effective packaging materials available on the market at their performance levels.

[0008] Any other material comparable to aluminum foil-based materials must be cost-effective in terms of raw materials, have comparable food preservation performance, and have comparable low complexity in transforming the material into a finished packaging laminate.

[0009] Another common motivation in the effort to develop non-aluminum foil materials for paperboard packaging of liquid foods is to develop prefabricated films or sheets with high and multiple barrier functions that can replace aluminum foil barrier materials in traditional laminated packaging materials, or combine multiple individual barrier layers in the laminate and adapt them to conventional lamination and manufacturing processes.

[0010] A preferred type of this alternative, more environmentally friendly and sustainable barrier material is a paper substrate coated with a barrier layer, produced by aqueous dispersion coating or vapor deposition coating on a thin paper carrier substrate. Various aqueous dispersion coating processes and vapor deposition coating processes exist, along with material formulations for achieving such coatings. There is a need for cost-effective “non-foil” (i.e., non-aluminum foil) barrier materials that offer improved barrier performance, particularly against gases (e.g., oxygen), for use in packaging laminates for liquid food packaging.

[0011] An earlier patent publication, WO2011 / 003565A1, disclosed a non-aluminum foil packaging material comprising a pre-coated and metallized kraft paper substrate for inductive heat sealing purposes. It recommended a fairly thick coating and inclusion of additional nano-clay particles in the pre-coating, and that further barrier coatings should be applied to the packaging laminate, for example, on the back of the paper substrate or on the main cardboard layer, to achieve good gas barrier properties. Such further barrier coatings would be required in this disclosure to compensate for the relatively low barrier properties provided by the metallized kraft paper.

[0012] An earlier patent publication, WO2017 / 089508A1, disclosed how to obtain further improved barrier properties from metallized paper in similar packaging laminates by selecting a paper substrate that provides optimal performance. This metallized paper substrate not only provides improved barrier properties but also demonstrates better stability of the metallized layer in inductive heat sealing.

[0013] However, further improvements are still needed in the oxygen barrier properties of similar coated paper and other cellulose-based substrates. Improvements are also needed in the recyclability and sustainability of the materials used. Summary of the Invention

[0014] Therefore, one object of the present invention is to provide an improved paper or cellulose-based substrate coated with a barrier layer for lamination into packaging materials.

[0015] A general object of the present invention is to provide a paper or cellulose-based substrate coated with a barrier layer that has good barrier properties and improved recyclability and sustainability to meet the needs of future sustainable liquid carton laminated packaging materials.

[0016] Another general object of the present invention is to provide packaging materials for oxygen-sensitive products, such as foil-free laminated packaging materials for liquid, semi-solid or wet foods, which do not contain aluminum foil but still have good gas barrier properties and other barrier properties, are suitable for long-term aseptic packaging and are cost-effective.

[0017] One specific objective is to provide a non-aluminum foil paper-based or cardboard-based compression packaging material that is cost-effective compared to aluminum foil barrier materials, and has good gas and water vapor barrier properties as well as recyclability and sustainable environmental characteristics, for use in the manufacture of packaging for long-term aseptic food storage.

[0018] Another object of the present invention is to provide a cost-effective, non-aluminum foil-based or paperboard-based, mechanically robust and heat-sealable packaging laminate with good gas and water vapor barrier properties and good interlayer adhesion for use in the manufacture of aseptic packaging containers for the long-term storage of liquid foods under environmental conditions to maintain their nutritional quality.

[0019] Therefore, according to the present invention, these objectives can be achieved by paper or cellulose-based substrates coated with barrier layers, laminated packaging materials, packaging containers, and methods of manufacturing packaging materials as defined in the appended claims.

[0020] Invention Summary

[0021] According to a first aspect of the invention, a cellulose-based substrate coated with a barrier layer, used as a barrier sheet in laminated packaging materials for liquid foods, comprises: a cellulose-based substrate; a barrier pre-coating applied to a first top side of the cellulose-based substrate, the barrier pre-coating being applied by dispersion coating or solution coating; and a barrier deposition coating further applied to the barrier pre-coating, the barrier deposition coating being applied by a vapor deposition method, wherein the cellulose-based substrate coated with the barrier layer further comprises a base pre-coating, the base pre-coating being different from the barrier pre-coating and applied to the cellulose-based substrate by dispersion coating or solution coating, and thus positioned adjacent to and in contact with the first top side of the cellulose-based substrate layer, and positioned below the barrier pre-coating, the cellulose-based substrate coated with the barrier layer being thus suitable for providing gas and water vapor barrier properties in such laminated packaging materials and packaging made therefrom.

[0022] In one embodiment, the barrier pre-coating comprises a polymer selected from vinyl alcohol polymers and copolymers, such as a polymer selected from polyvinyl alcohol (PVOH) and ethylene vinyl alcohol (EVOH), and the barrier deposition coating is a vapor-phase deposition coating, such as a material selected from metals, metal oxides, inorganic oxides, and carbon coatings.

[0023] In another embodiment, the barrier deposition coating is a vapor-deposited coating selected from aluminum metallization coatings and aluminum oxide (AlOx), and preferably it is an aluminum metallization coating.

[0024] According to a second aspect of the invention, a laminated packaging material is provided, comprising a cellulose-based substrate coated with a barrier layer of the invention. The laminated packaging material may further comprise a first outermost liquid-tight heat-sealable polyolefin layer and a second innermost liquid-tight heat-sealable polyolefin layer.

[0025] For the purpose of packaging liquid food in paper boxes, the laminated packaging material may also include a main layer of paper or paperboard or other cellulose-based material, a first outermost liquid-tight heat-sealable polyolefin layer, a second innermost liquid-tight heat-sealable polyolefin layer, and the cellulose-based substrate coated with the barrier layer is disposed inside the main layer of paper or paperboard between the main layer and the innermost layer.

[0026] In a third aspect of the invention, a packaging container comprising the laminated packaging material of the invention is provided for packaging liquid, semi-solid, or wet food. According to one embodiment, the packaging container is at least partially made of the laminated packaging material of the invention, and according to another embodiment, it is entirely made of the laminated packaging material.

[0027] In a fourth aspect of the invention, a method for manufacturing a cellulose-based substrate coated with a barrier layer is provided, comprising: a first step of providing the cellulose-based substrate as a moving roll in a roll-to-roll system; a second step of applying a first dispersion or solution of a base layer pre-coating composition to the moving cellulose-based substrate, followed by drying the applied base layer pre-coating by forced evaporation; a third step of applying a second dispersion or solution of a barrier pre-coating composition having a different composition from the base layer pre-coating composition to the base-coated moving cellulose-based substrate, followed by drying the applied barrier pre-coating by forced evaporation; and a fourth step of further depositing a barrier deposition coating onto the barrier pre-coated cellulose-based substrate by a vapor deposition coating operation.

[0028] Until now, it has been believed that improving gas barrier properties from paper coated with a barrier layer should be achieved by either sourcing a better cellulose-based substrate that inherently provides gas barrier properties when further laminated to the polymer layer, or by coating a thicker layer with more polymers possessing inherent gas barrier properties. However, it has recently become clearer that the surface portion of the cellulose-based substrate plays a crucial role in the optimal performance of the subsequently applied gas-barrier coating. Therefore, this can be achieved by adding a further base coat to the surface of the cellulose-based substrate, followed by the application of the barrier coating. It can be seen that the barrier quality of the cellulose-based substrate itself does not need to be as high, and the amount of gas-barrier polymers applied as a barrier pre-coating can even be reduced. Even with this base coat, although it does not itself possess significant barrier properties—that is, the base material does not have significant inherent barrier properties—the resulting barrier properties in the packaging laminate are still very high. A base coat composition should be selected to provide a homogeneous, uniform, dense, and compatible surface to receive a further dispersed gas barrier pre-coating, which will then receive a further vapor-deposited barrier coating in the next step. However, the material selected for the base coat does not need to have inherent gas barrier properties.

[0029] The base pre-coating material advantageously comprises a polymer selected from starch, modified starch, and cellulose ether.

[0030] Therefore, the cellulose-based substrate coated with a barrier layer obtained by the above method and coating structure provides improved barrier properties for the laminated packaging material containing it, and can also endow it with improved recyclability and sustainability.

[0031] Detailed description

[0032] The term "long-term storage" as used in conjunction with this invention means that the packaging container should be able to maintain the quality (i.e., nutritional value, hygiene and safety, and taste) of the packaged food under environmental conditions for at least one or two months, for example at least three months, preferably longer, for example six months, for example twelve months, or longer.

[0033] The term "packaging integrity" generally refers to the airtightness of packaging, that is, the leak-proof or breakage-proof nature of the packaging container. This term includes the packaging's resistance to the invasion of microorganisms (such as bacteria, dirt, and other substances) that can spoil the filled food and shorten the package's intended shelf life.

[0034] A major contribution of laminated packaging materials to the integrity of packaging comes from the good internal adhesion between adjacent layers. Another contribution comes from the material's resistance to defects (such as pinholes, cracks, etc. within each layer itself), and yet another contribution comes from the strength of the sealing joints, through which the materials are sealed together during the formation of the packaging container. Therefore, for the laminated packaging material itself, integrity performance primarily focuses on the adhesion between each laminate layer and its adjacent layers, as well as the quality of each individual layer. Regarding the sealing of the packaging, integrity primarily focuses on the quality of the sealing joints, which is ensured by the efficient operation of the filling machine and robust sealing operation, which in turn is guaranteed by the well-suited heat-sealing properties of the laminated packaging material.

[0035] The term "liquid or semi-liquid food" generally refers to a food having a liquid content, which may optionally contain food fragments. Dairy products and milk, soy, rice, grain and seed beverages, fruit juices, nectar, non-carbonated beverages, energy drinks, sports drinks, coffee or tea beverages, coconut water, wine, soup, jalapenos, tomatoes, sauces (such as pasta sauce), beans, and olive oil are some non-limiting examples of the intended food.

[0036] The term "sterile" in relation to packaging materials and containers refers to conditions under which microorganisms are eliminated, inactivated, or killed. Examples of microorganisms are bacteria and spores. Aseptic processes are typically used when products are aseptically packaged in containers. To achieve sustained sterility throughout the shelf life of the packaging, the integrity of the packaging is, of course, crucial. Furthermore, to achieve a long shelf life for filled foods, it may also be important for the packaging to have barrier properties against gases and vapors (such as oxygen) to maintain its original flavor and nutritional value, such as its vitamin C content.

[0037] The term "main layer" generally refers to the thickest layer or the layer containing the most material in a multilayer laminate, i.e., the layer that contributes the most to the mechanical properties and dimensional stability of the laminate (e.g., cardboard or hardboard) and the packaging container folded from the laminate. It can also refer to a layer that provides a greater thickness gap in a sandwich structure, which further interacts with stabilizing facet layers on each side of the main layer to achieve sufficient mechanical properties and dimensional stability.

[0038] Thickness measurements were performed using a Titan 80-300 FEI instrument via transmission electron microscopy. Samples were prepared using ultrathin sectioning on a Leica EM UC6 microtome.

[0039] OTR is measured using the Oxtran 2 / 21 (Mocon) device, which is based on a coulomb sensor.

[0040] The method used to determine OTR determines the amount of oxygen per surface and per unit time when passing through a material at a specific temperature and given atmospheric pressure over a specific time period (i.e., within 24 hours in an atmosphere of 100% oxygen).

[0041] Water vapor transmission rate (WVTR) was measured using a Permatran 3 / 33 (Mocon) instrument (standard: ASTM F 1249-13, using a modulated infrared sensor for relative humidity detection and WVTR measurement) at 38°C and 90% drive force.

[0042] The substrates suitable for the barrier coating of this invention are not limited to a certain type of paper, but also include other cellulose-based substrates, which are based on any type of natural cellulose, cellulose fiber, or fibrillated cellulose. However, this invention is not applicable to substrates made of plastics or polymers, such as films made of regenerated cellulose.

[0043] To date, from an oxygen barrier perspective, paper or cellulose-based substrates with a surface smoothness of 200 ml / min or less (e.g., about 150 ml / min or less) on the coated surface (“top surface” or “printed surface”) can provide particularly good structures with barrier layers according to the invention. However, it should also be recognized that the novel combination of the pre-coating and barrier coating of the invention can more or less improve the barrier properties of any paper substrate beyond what has been previously thought possible.

[0044] To facilitate the final coating of the barrier layer using a vapor deposition process, and for reasons of efficiency and production economy, and to avoid coating blistering (caused by air trapping within the porous cellulose-based substrate), the substrate needs to be very thin, for example, 60 g / m². 2 Or below, for example, 50g / m 2 Or below, preferably 45g / m 2 Or less, and more preferably 40 g / m 2 Or below. On the other hand, when thinner or with a weight below 30g / m³ 2 When a cellulose-based substrate is coated with a wet dispersion and subsequently dried, its mechanical strength may be too weak and / or its dimensional stability poor, leading to shrinkage or curling problems. Therefore, a basis weight of 30 to 50 g / m³ is more preferable. 2 For example, the optimal value is 35 to 45 g / m³. 2 The paper.

[0045] To achieve optimal barrier performance with minimal amounts of barrier material, it has been found to date that a thin pre-coating with a gas-barrier polymer is necessary when applying a barrier deposition coating to a thickness only on the nanometer scale on paper or fiber-based substrates. Preferred working barrier pre-coatings are selected from vinyl alcohol polymers and copolymers, which possess inherent gas-barrier properties, are food-safe, and are environmentally sustainable in terms of recyclability and industrial coating and lamination processes. Such polymers are water-dispersible and / or water-soluble and can be applied via an aqueous “dispersion coating” process or a so-called “liquid film coating” process. Non-aqueous or only partially aqueous coating compositions, such as those based on alcohols or mixtures of alcohols and water, are also suitable for achieving the good results of this invention. However, they may be less suitable from an environmental sustainability perspective.

[0046] The process applicable to coating low-dry-content polymer dispersions / solution compositions is broadly defined as any suitable wet coating method, such as gravure roller coating, air spraying, airless spraying, reverse roller coating, wire rod coating, lip coating, air knife coating, curtain coating, spraying, dip coating, and brush coating. The experiments of this invention were conducted using gravure coating, but it is believed that any of the aforementioned liquid film coating methods that contribute to producing a smooth and uniform coated surface are suitable for carrying out this invention.

[0047] Therefore, the preferred barrier pre-coating compositions are based on two of the most common types of polymers and copolymers suitable for dispersion coatings, which are based on vinyl alcohol monomers, namely polyvinyl alcohol (PVOH) and ethylene-vinyl alcohol (EVOH).

[0048] Preferably, the gas barrier polymer is PVOH because it offers good film-forming properties, gas barrier properties, cost efficiency, food compatibility, and odor barrier properties.

[0049] Gas barrier compositions based on PVOH perform best when the degree of saponification of PVOH is at least 98%, preferably at least 99%, although PVOH with a lower degree of saponification will also provide oxygen barrier properties. On the other hand, EVOH may be advantageous by providing some moisture-proof properties to the barrier material because the copolymer contains ethylene monomer units. The amount used depends on the choice of EVOH grade, but compared to PVOH, this will come at the cost of sacrificing some of the material's inherent oxygen barrier properties. Conventional EVOH polymers are typically used for extrusion and cannot be dispersed or dissolved in aqueous media to produce 3.5 g / m³ gas barrier compositions. 2Barrier films coated with a thin liquid film, or the following: EVOH is believed to contain a substantial amount of vinyl alcohol monomer units to be dispersible in water, and its properties should be as close as possible to those of liquid film coating grades of PVOH. Therefore, extruded EVOH layers cannot replace liquid film-coated EVOH because the inherent properties of extruded EVOH layers are less similar to those of PVOH compared to EVOH grades used for extrusion coating, and because it cannot be produced at a concentration below 4 g / m³ by extrusion coating or extrusion lamination. 2 The cost-effectiveness is applied to a single layer.

[0050] The barrier pre-coating composition may also contain an inorganic layered compound, such as exfoliated nanoclay particles, like bentonite, at about 1 to 20% by weight based on the dry coating weight. Therefore, the barrier layer may comprise a polymer at about 99 to 80% by weight based on the dry coating weight. The gas barrier composition may also contain additives, such as dispersing stabilizers, preferably not exceeding about 1% by weight based on the dry coating weight. The total dry content of the composition is preferably 5 to 15% by weight, more preferably 7 to 12% by weight.

[0051] Another possible additive in the barrier pre-coating composition can be a polymer or compound having functional carboxylic acid groups to improve the water vapor and oxygen barrier properties of the PVOH coating. Suitably, such polymers having functional carboxylic acid groups are selected from ethylene acrylate copolymers (EAA) and ethylene methacrylate copolymers (EMAA) or mixtures thereof. In one embodiment, such a barrier layer mixture can consist essentially of PVOH, EAA, and an inorganic layered compound. The barrier layer may include an amount of EAA copolymer of about 1-20% by weight based on the dry coating weight.

[0052] It is believed that some further improvements in oxygen and water barrier properties may be due to the esterification reaction of PVOH and EAA at elevated drying temperatures, whereby the PVOH is crosslinked by hydrophobic EAA polymer chains, thereby incorporating them into the structure of the PVOH. Alternatively, crosslinking can be induced by the presence of multivalent compounds, such as metal compounds, like metal oxides. However, such mixtures are more expensive due to the cost of additives and may not be the most desirable option from a recyclability perspective.

[0053] Therefore, while it is preferable to use a barrier pre-coating made of pure PVOH or EVOH composition, advantageous gas barrier results can also be obtained with a barrier pre-coating containing other additives as described above.

[0054] It can be in the form of 0.1 to 3 g / m³ dry weight. 2 The total amount is preferably 0.5 to 2 g / m³ (dry weight). 2 Apply a barrier pre-coating to the total amount. Less than 0.1 g / m³2 It will be completely impossible to achieve gas barrier performance, and it will be higher than 3g / m 2 Pre-coating does not provide cost-effectiveness for packaging laminates because the barrier polymer is typically expensive, and the energy cost of evaporating the liquid is also high. PVOH at 0.5 g / m 2 The above achieved identifiable oxygen barrier levels, and at 0.5 and 2 g / m³. 2 A good balance is achieved between barrier performance and cost.

[0055] In one embodiment, the barrier pre-coating can be applied as two partial layers in two consecutive steps with intermediate drying. When applied as two partial layers, the appropriate application amount for each layer is 0.1 to 2 g / m². 2 Preferably 0.5 to 1.5 g / m 2 This allows for a higher quality overall layer to be obtained with a lower amount of liquid-gas barrier composition. More preferably, each of the two partial layers is prepared at a concentration of 0.5 to 1 g / m³. 2 The amount applied.

[0056] In one embodiment, the barrier pre-coating has been applied by dispersion coating or solution coating at a dry weight of 0.5 to 2 g / m³. 2 The amount applied is preferably 0.5 to 1.5 g / m³ (dry weight). 2 The amount applied.

[0057] An unexpected improvement to this invention is that the barrier pre-coating should not be applied directly to the paper or cellulose-based substrate, but rather a first base coat should be applied using different polymers and compositions to prepare the substrate surface for the barrier pre-coating. It is not fully understood why, i.e., what the physical and / or chemical conditions at the interface between the two pre-coatings are, are the primary factors in improving the resulting barrier performance, but it is believed that the specific properties of the aqueous starch composition promote a dense and uniform base top surface for further coating and promote compatible adhesion chemistry and wettability for the subsequent application of the polyvinyl alcohol-based barrier pre-coating.

[0058] The base coat should be applied directly to and adjacent to the paper or cellulose-based substrate. Paper allows moisture to migrate outwards through the laminated packaging material, and the base coat also allows this water vapor migration. Therefore, there is no undesirable moisture retention near the PVOH or EVOH moisture-sensitive barrier pre-coating. Any moisture that migrates through the material from the interior of the liquid food within the packaging will simply be further transported to the outside of the packaging container through the paper layers and the cardboard body of the laminated packaging material. The cellulose-based substrate and the cardboard body “breathe” moisture from the barrier pre-coating, thus keeping the moisture content within the barrier pre-coating substantially constant over time.

[0059] For the aforementioned functions of smoothing, moisture transport, and surface compatibility, the base pre-coating preferably comprises a polymer selected from starch, modified starch, and cellulose ethers. These polysaccharide compounds have similar properties in this regard and will all provide the same advantages.

[0060] More specifically, the base pre-coating may comprise materials selected from the group consisting of starch, modified starch, methylcellulose, ethylcellulose, carboxymethylcellulose (CMC), hydroxyethylcellulose (HEC), hydroxypropylcellulose (HPC), hydroxypropyl methylcellulose (HPMC), and sodium carboxymethylcellulose (NaCMC). These plant-based compounds will provide the best expected results consistent with the above, and also involve ease of recycling and sustainability.

[0061] Suitable starch materials or starch derivatives can be oxidized starch, cationic starch, and hydroxypropylated starch. Examples of such modified starches are hypochlorite oxidized potato starch (Raisamyl306 from Raisio) and hydroxypropylated corn starch (Cerestar 05773), however other forms of starch can also provide the desired properties in a base pre-coating.

[0062] Furthermore, because this base coat can reduce the amount of barrier pre-coating while still achieving the same level of barrier performance, a slightly higher level of sustainability can be achieved, since the preferred base coat compound may be more or less entirely derived from plants. The base coat composition of natural starch will, for example, be 100% plant-based and 0% fossil-derived.

[0063] In one implementation, the total application amount of the base coat and the barrier coat is approximately 1 to approximately 4 g / m³ (dry weight). 2 Preferably, the dry weight is 1.5 to about 3 g / m³. 2 .

[0064] In a further embodiment, the base pre-coating has been applied by aqueous dispersion coating or solution coating at a dry weight of 0.5 to 2 g / m³. 2 The amount applied is preferably 0.5 to 1.5 g / m³ (dry weight). 2 The amount applied.

[0065] The vapor-deposited barrier coating that is ultimately applied to the barrier pre-coated surface is applied by means of physical vapor deposition (PVD) or chemical vapor deposition (CVD), such as by plasma-enhanced chemical vapor deposition (PECVD).

[0066] In one embodiment, the material of the vapor-deposited coating is selected from metals, metal oxides, inorganic oxides, and carbon coatings.

[0067] In another embodiment, the barrier deposition coating is selected from aluminum metallization coating and aluminum oxide (AlO). x The vapor-deposited coating in the group, and preferably an aluminum metallization coating.

[0068] These thin vapor-deposited coatings are nanoscale in thickness, meaning they have thicknesses best suited for nanometer-scale measurements, such as 5 to 500 nm (50 to 100 nm). (e.g., 5 to 200 nm, more specifically 5 to 100 nm, e.g., 5 to 50 nm).

[0069] Typically, below 5nm, the barrier performance may be too low to be usable, while above 200nm, such as above 100nm, such as above 50nm, depending on the type of vapor-deposited coating, the barrier coating may be less flexible and therefore more prone to cracking when applied to flexible substrates, and the cost will also be higher.

[0070] In one embodiment, the barrier deposition coating is applied to a thickness of 10 to 80 nm, for example 10 to 50 nm, or for example 10 to 45 nm.

[0071] A common type of vapor-deposited coating (which typically has some barrier properties, particularly water vapor barrier properties) is the so-called metallized coating, such as aluminum physical vapor deposition coating.

[0072] This vapor-deposited layer, which is essentially composed of aluminum, can have a thickness of 5 to 50 nm, more preferably 5 to 40 nm, which corresponds to less than 1% of the aluminum material present in aluminum foil of a conventional thickness (i.e., 6.3 μm) used for packaging. While vapor-deposited metal coatings require much less metal material, they can only provide a low level of oxygen barrier properties at best and need to be combined with other gas barrier materials to provide a final laminate with sufficient barrier properties. Alternatively, it can be supplemented with another gas barrier layer that does not have water vapor barrier properties but is quite sensitive to moisture.

[0073] Other examples of vapor-deposited coatings are alumina (AlO2). x Al2O3 and silicon dioxide (SiO2) x ) Coating. Generally, such PVD coatings are more brittle and less suitable for bonding to packaging materials by lamination, while metallized layers are an exception, although they are made by PVD, they do have the mechanical properties suitable for laminated materials.

[0074] Typically, due to the nature of the metallization coating process used, aluminum metallization layers inherently have a thin surface portion composed of aluminum oxide.

[0075] In one embodiment, such an aluminum metallization layer has been applied to an optical density (OD) of 1.8 to 2.5, preferably 1.9 to 2.2. Below an OD of 1.8, the barrier properties of the metallization film may be too low. On the other hand, above 2.5, the metallization layer becomes brittle, and the thermal stability during the metallization process is lower due to the higher heat load when metallizing the substrate film over a longer period. Coating quality and adhesion may be negatively affected. Optical density is measured in production using a densitometer, i.e., an instrument that uses the principle of diffuse light transmission (e.g., from Macbeth, Tobias, or similar instruments). This instrument is suitable for measuring the optical density value of the aluminum-coated metallization film. Within the measurement range of 0 to 6.60 OD, the accuracy and precision of the measurement are approximately + / - 0.2 OD and approximately + / - 0.01 OD, respectively.

[0076] In laboratory measurements, a spectrophotometer can alternatively measure light transmission across the entire visible spectrum (380-800 nm). According to the formula OD = -log 10 (I1 / I0), the optical density is calculated based on the transmittance (T) value at 560nm, and the obtained value is equally accurate (+ / -0.2OD), which is comparable to the value of the transmittance meter.

[0077] Other coatings can be applied via plasma-enhanced chemical vapor deposition (PECVD), where the vapor of a compound is deposited onto a substrate in a more or less oxidizing environment. For example, silicon oxide coatings (SiO2) x It can also be applied via PECVD process, and then very good barrier properties can be obtained under certain coating conditions and gas formulations.

[0078] DLC defines a class of amorphous carbon materials (diamond-like carbon) that exhibit some of the typical properties of diamond. Preferably, hydrocarbon gases (e.g., acetylene or methane) are used as process gases in the plasma for the production of coatings of amorphous hydrogenated carbon barrier layers (i.e., DLC) applied via a PECVD vacuum process. DLC coatings applied under vacuum via PECVD provide good adhesion to adjacent polymer or adhesive layers in laminated packaging materials. Particularly good adhesion to adjacent polymer layers can be obtained using polyolefins, particularly polyethylene and polyethylene-based copolymers.

[0079] Vapor-deposited barrier coatings are preferably applied by vacuum vapor deposition, but may also be applied less preferably by other methods known in the art that have lower productivity and lower coating quality, such as electroplating or sputtering. The most preferred metal according to the invention is aluminum, but any other metal capable of vacuum deposition, electroplating, or sputtering may also be used. Therefore, less common metals such as Au, Ag, Cr, Zn, Ti, or Cu are less preferred alternatives. Typically, thin coatings of metal or mixtures of metal and metal oxides provide barrier properties against water vapor and are used when the desired function is to prevent water vapor from migrating into and through multilayer films or packaging laminates. Preferably, for the purpose of manufacturing food packaging materials, the metal in the metallized or inorganic metal coating is aluminum (Al).

[0080] The paper or cellulose-based substrate coated with a barrier layer obtained by the above method provides excellent low OTR and low WVTR, and has proven suitable for lamination into laminated packaging materials and further for folding and sealing operations to form such laminated materials into packages.

[0081] The laminated packaging material comprising a cellulose-based substrate coated with a barrier layer further comprises a first outermost protective material layer (22a; 22b) and a second innermost liquid-tight heat-sealable material layer (23a; 23b; 23b'). The second innermost liquid-tight heat-sealable material layer (23a; 23b; 23b') may comprise or be made of a polyolefin polymer. The first outermost protective material layer may be transparent to allow the printed decorative pattern on the outside of the body layer to be seen. It may also comprise or be made of a polyolefin polymer.

[0082] Therefore, a cardboard-based laminated packaging material for liquid food packaging may include a paper or paperboard body layer, a first outermost protective material layer, a second innermost liquid-tight heat-sealable material layer, and a paper or cellulose-based substrate coated with a barrier layer, wherein the paper or cellulose-based substrate coated with a barrier layer is disposed inside the paper or paperboard body layer, facing the interior of the packaging container made of the packaging material, and is located between the body layer and the second innermost liquid-tight heat-sealable material layer.

[0083] The cardboard-based laminated packaging material may include a paper or paperboard body layer, a first outermost liquid-tight heat-sealable polyolefin layer, a second innermost liquid-tight heat-sealable polyolefin layer, and a paper or cellulose-based substrate coated with a barrier layer, the paper or cellulose-based substrate coated with the barrier layer being disposed inside the paper or paperboard body layer, facing the interior of the packaging container made of the packaging material, and between the body layer and the innermost layer.

[0084] The paper or paperboard body layer used in this invention typically has a thickness of about 100 μm to about 600 μm and a g / m² of about 100-500 g / m³. 2Optimal 200-300g / m 2 The surface weight, and can be regular paper or cardboard with suitable packaging quality.

[0085] For low-cost, aseptic, long-term packaging of liquid foods, thinner packaging laminates with a thinner paper core layer can be used. Packaging containers made from this type of laminate are not folded but rather resemble pillow-shaped pouches. The paper suitable for this type of pouch packaging typically has a strength of approximately 50 to approximately 140 g / m³. 2 Preferably about 70 to about 120 g / m 2 More preferably 70 to about 110 g / m 2 The surface weight. Since the substrate coated with the barrier layer in this invention can itself bring a certain degree of stability to the laminated material, the paper layer corresponding to the "body" layer can be thinner, and through interlayer interaction with the cellulose-based substrate with the barrier layer, a laminated packaging material with the required mechanical properties can still be produced.

[0086] The paper or cellulose-based substrate coated with a barrier layer can be bonded to the main layer via an intermediate adhesive or thermoplastic polymer adhesive layer, thereby bonding the uncoated surface of the paper coated with the barrier layer to the main layer. According to one embodiment, the adhesive layer is a polyolefin layer primarily comprising ethylene monomer units, such as, in particular, a polyvinyl polyolefin copolymer or blend layer. The adhesive layer bonds the main layer to the paper or cellulose-based substrate coated with the barrier layer by melt-extruding and laminating an adhesive polymer layer between the main layer roll and the cellulose-based substrate roll, and simultaneously pressing the three layers together as they advance through the gap of the laminating rolls, thereby providing a laminated structure through extrusion lamination.

[0087] In another embodiment, the cellulose-based substrate coated with the barrier layer can be bonded to the base layer by wet-applying an aqueous dispersion of an adhesive composition containing a viscous polymer binder to one of the surfaces of the rolls to be laminated, and pressing the two paper rolls together as they advance through the gap of the laminating rolls, thereby providing a laminated structure through wet lamination. During subsequent lamination, the moisture in the aqueous viscous 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 binder is selected from acrylic polymers and copolymers, starch, cellulose and polysaccharide derivatives, and polymers and copolymers of vinyl acetate and vinyl alcohol. For optimal environmental and sustainability properties, viscous binders derived from plant or non-fossil sources are preferred.

[0088] Suitable thermoplastics for both the outermost and innermost heat-sealable liquid-tight layers are polyolefins, such as homopolymers or copolymers of polyethylene and polypropylene, preferably polyethylene, and more preferably low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), mono-site catalyst metallocene polyethylene (m-LLDPE), and blends or copolymers thereof. According to one embodiment, the outermost heat-sealable liquid-tight layer is LDPE, while the innermost heat-sealable liquid-tight layer is a blend of m-LLDPE and LDPE to obtain optimal lamination and heat-sealing properties.

[0089] The same thermoplastic polyolefin-based materials (particularly polyethylene) listed for the outermost and innermost layers are also suitable for the adhesive layers within the laminate, i.e., the adhesive layer between the host layer or core layer (e.g., paper or paperboard) and the barrier film or sheet. In one embodiment, the thermoplastic adhesive layer may be a polyethylene layer, such as a low-density polyethylene (LDPE) layer.

[0090] In another embodiment, the second innermost liquid-tight heat-sealable polyolefin layer is a pre-formed film containing the same or similar polyolefins as described above to improve the robustness of the mechanical properties of the packaging material. Due to the manufacturing processes in blown film and film casting operations, and optional subsequent film orientation steps, the polymer of such films acquires different properties than that of (co)extruded coated polyolefin layers. Such pre-formed polymer films thus contribute to the mechanical robustness of the laminated packaging material and the mechanical strength and packaging integrity of the packaging containers formed and filled by the laminated packaging material.

[0091] According to alternative embodiments, a suitable adhesive or bonding layer within the laminate (such as, for example, between the main layer or core layer and the cellulose-based substrate coated with a barrier layer, or between the outer heat-sealable layer and the paper substrate coated with a barrier layer) is a so-called viscous thermoplastic polymer (such as a modified polyolefin), primarily based on LDPE or LLDPE copolymers or graft copolymers having monomer units containing functional groups (e.g., carboxyl or glycidyl functional groups) (e.g., (meth)acrylic acid monomers or maleic anhydride (MAH) monomers) (i.e., ethylene-acrylic acid copolymer (EAA) or ethylene-methacrylic acid copolymer (EMAA)), ethylene-(meth)acrylic acid glycidyl ester copolymer (EG(M)A), or MAH-grafted polyethylene (MAH-g-PE). Another example of such a modified polymer or adhesive polymer is a so-called ionomer or ionomer polymer. Preferably, the modified polyolefin is ethylene-acrylic acid copolymer (EAA) or ethylene-methacrylic acid copolymer (EMAA).

[0092] The laminated packaging materials prepared according to the above method provide good integrity when transformed into filled packaging containers due to the good adhesion between adjacent layers within the laminated structure and the individual and combination of high-quality barrier coatings and barrier pre-coatings. Particularly for the packaging of liquids and wet foods, an important conclusion is that the interlayer adhesion and oxygen barrier properties within the laminated packaging materials are maintained even under wet packaging conditions.

[0093] According to a further embodiment, the packaging container formed of laminated packaging material can be partially sealed, filled with liquid or semi-liquid food, and then sealed by the packaging material itself (optionally combined with the plastic opening or top portion of the packaging).

[0094] In summary, due to the improved barrier properties provided, cellulose-based substrates coated with barrier layers, as defined in this invention, and laminated packaging materials comprising such barrier-coated cellulose-based substrates, can achieve robust and reliable packaging for liquid foods with long shelf lives and storage. The laminated packaging material structure is more suitable for forming foldable packaging, both because of improved adhesion between the substrate and the barrier coating, and because of improved contribution of the barrier coating substrate itself to gas barrier performance. This may also be due to improved cohesion and adhesion between the pre-coating and the barrier coating in the barrier-coated cellulose-based substrate. Attached Figure Description

[0095] The preferred embodiments of the present invention will now be described with reference to the accompanying drawings, wherein:

[0096] Figure 1 The diagram schematically shows a cross-section of a cellulose-based substrate coated with a barrier layer according to an embodiment of the present invention.

[0097] Figure 2a A schematic cross-sectional view of a laminated packaging material according to the present invention is shown, the laminated packaging material comprising... Figure 1 Cellulose-based substrate coated with a barrier layer

[0098] Figure 2b A schematic cross-sectional view of another laminated packaging material is shown, which includes... Figure 1 Cellulose-based substrate coated with a barrier layer

[0099] Figure 3a The diagram schematically illustrates a method for dispersing and coating a base or barrier pre-coating composition onto a cellulose-based substrate.

[0100] Figure 3b The diagram schematically illustrates a method for melt-extruding (co-)coating a thermoplastic, heat-sealable, and liquid-tight polymer layer onto a roll substrate to form the innermost and outermost layers of the packaging laminate of the present invention.

[0101] Figure 4a A schematic diagram of an apparatus for physical vapor deposition (PVD) coating on a substrate film using a solid metal evaporation plate is shown.

[0102] Figure 4b A schematic diagram of an apparatus for plasma-enhanced chemical vapor deposition (PECVD) coating on a substrate film using magnetron plasma is shown.

[0103] Figure 5a , 5b 5c and 5d show typical examples of packaging containers produced from laminated packaging materials according to the present invention, and

[0104] Figure 6 This demonstrates the principle of how such packaging containers can be manufactured from packaging laminates through a continuous, roller-feed, forming, filling, and sealing process. Detailed Implementation

[0105] Example

[0106] Example 1

[0107] As shown in Table 1, in a small-scale trial, two different paper substrates suitable for oil-resistant packaging types were coated with a base pre-coating and / or a barrier pre-coating, without further metallized aluminum barrier deposition on the barrier pre-coating. Subsequently, the coated paper substrates were laminated into the following packaging laminate structure:

[0108] / / External 12g / m 2 LDPE / Duplex CLC 80mN, 200g / m 2 Cardboard body layer / 3-4g / m 2 Water-based PVAc adhesive / paper pre-coated with a barrier layer (as listed in Table 1) / 6 g / m 2 EAA viscous polymer / 22g / m 2 Internal heat-sealing layer of LDPE and m-LLDPE blends / /

[0109] Duplex CLC paperboard is a conventional type of clay-coated paperboard, and m-LLDPE is metallocene-catalyzed linear low-density polyethylene. The side of the paper substrate coated with the barrier layer points inward in the laminated structure (corresponding to the interior of the packaging container made of the laminated material). The viscous polymer EAA and the innermost heat-sealable layer are co-extruded together onto the barrier-coated paper, and the outermost LDPE layer is extruded and coated onto the outside of the paperboard. The paperboard body layer is laminated onto the barrier-coated paper using a small amount of water-based adhesive containing polyvinyl acetate for wet lamination, without any intermediate drying steps.

[0110] Oxygen transport was measured using an Oxtran Mocon 2 / 21 device (a coulometric sensor-based device) at 23°C and 50% and 80% RH (relative humidity), respectively, over a 24-hour period, at 1 atmosphere of 100% oxygen (air at 1 atmosphere contains only 20% oxygen), at cc / m 2 Report to the unit.

[0111] Paper A is an oil-resistant paper from Nordic Paper with a dense, compact surface, and has been certified as "Super Oil-resistant". "WS Parchment" has a weight of 38g / m³. 2 .

[0112] Paper B is an oil-resistant paper from Arjo Wiggins called "Clearpack," with a basis weight of 46g / m². 2 .

[0113] The surface roughness of the paper on the top side (i.e. the side to be coated with the barrier layer) was measured to be approximately 200-300 ml / min Bendtsen and approximately 150 ml / min Bendtsen, respectively.

[0114] The corresponding paper was therefore coated only with the base pre-coating and / or barrier pre-coating according to Table 1 (i.e., coated with a dispersed pre-coating), and then laminated into the same laminated packaging material structure. Pre-coating and lamination operations were performed on a test scale to produce laminated packaging material structures from pre-coated paper, and the oxygen permeability of the resulting flat samples of the packaging material was measured.

[0115] Table 1

[0116]

[0117]

[0118] Therefore, the barrier papers listed in Table 1 are laminated into the standardized laminated packaging material structure described above, either uncoated or disperse-coated (this type of coating method is commonly referred to as "liquid film coating," which is suitable for pre-coating a low dry weight of an aqueous dispersion or polymer solution onto a substrate). The base coat and barrier coat are applied in steps 1-3 as listed, with each coat having a dry coating weight of approximately 1 g / m². 2 There is an intermediate drying step between each coating. Two types of aqueous dispersions and / or solutions were used, both from the Avebe brand. An aqueous dispersion of natural potato starch, and a polyvinyl alcohol (PVOH) solution from Kuraray with a degree of hydrolysis of at least 98%, i.e. 6-98. When a starch pre-coating and a PVOH pre-coating are applied together for the purpose of forming a barrier layer paper, the starch coating is applied as a first base pre-coating, which is dried in an online dryer apparatus, followed by the application of another PVOH barrier pre-coating, and then dried in an online dryer in a second drying step. The dispersion is applied by gravure coating in a pilot-scale apparatus, and the dry content of the PVOH aqueous dispersion is about 15% by weight. The temperature of the substrate surface is adjusted to about 60 to about 80°C during each drying operation.

[0119] The dry content and viscosity of the starch dispersion are selected to allow for low dry starch content application at industrial speeds via gravure coating. A base pre-coating is applied as a rich, well-adhesive, dense, and uniform base pre-coating, enabling the subsequent application of a uniform, small-volume barrier dispersion pre-coating. The resulting uniform and smooth surface of the dried barrier pre-coating then allows for the application of a further high-quality vapor-deposited coating that is coherent, uniform, pinhole-free, and adheres well to the dried barrier pre-coating surface.

[0120] Therefore, the coating is applied in 2-3 consecutive coating steps, achieving approximately 1 g / m² in each coating step. 2 The dry matter weight is used to dry each applied coating between coating steps.

[0121] From the sample laminates containing paper substrates pre-coated with a base layer and / or pre-coated with a barrier coating according to Table 1, the following conclusions can be drawn: One or two starch coatings only improve the oxygen barrier properties of each pre-coated paper in the laminate to a certain extent, but this improvement is greater in the case of paper A, which has a greater initial surface roughness and exhibits lower inherent oxygen barrier properties when laminated into a multi-layered structure. Pre-coated papers with only two or three PVOH coatings have further improved barrier properties compared to papers with only a starch coating, partly because starch inherently contributes less due to its inherent gas barrier properties. However, significant further improvements were observed when the two types of pre-coatings were combined in the order defined in samples 7 and 14, namely the first starch base layer pre-coating and the second PVOH barrier pre-coating. This further, unexpected improvement in the oxygen barrier properties of the resulting final laminate was even more significant when paper B was used, i.e., the paper had higher smoothness and higher inherent barrier properties. Then, compared with samples 12-13, the OTR of sample 14 was even further reduced by 50%, which was achieved by applying only a pre-coated PVOH layer with higher barrier properties.

[0122] Example 2

[0123] Furthermore, in a more comprehensive production run, similar barrier coating experiments were conducted on two types of paper, A and B, as listed in samples 7 and 14 of Table 1. Papers pre-coated with barrier layers, having a first base pre-coating and a second barrier pre-coating, were thus metallized and subsequently laminated in the same manner into multilayer laminated packaging material structures. The dispersion coating operation was performed at speeds of 400 to 600 m / min, and these coatings were applied in two consecutive coating steps, resulting in a dry matter weight of approximately 1 g / m³. 2 Each applied coating is dried between coating steps. As in Example 1, drying is performed at a substrate surface temperature of about 60 to about 80°C. In subsequent individual coating operations, a metallized barrier coating is applied to the barrier pre-coating by physical vapor deposition to achieve an optical density of about 2.0, as measured by a light transmittance densitometer, and a thickness of about 40 nm.

[0124] The packaging laminate samples were also prepared from pre-coated paper substrates without the application of a metallized aluminum coating.

[0125] The results of the experiment are listed in Table 2.

[0126] Table 2

[0127]

[0128]

[0129] Through various physical experiments, it can be seen that by applying a further metallization coating, the oxygen barrier performance was further improved (lower oxygen transmission) in the sample corresponding to sample 7 in Table 1 (i.e., through the barrier pre-coating on paper A) and in the sample corresponding to sample 14 (i.e., through the barrier pre-coating on paper B). See samples 2.3, 2.5, and 2.6 for paper A, and samples 2.1, 2.2, and 2.4 for paper B.

[0130] No significant effect was found on the obtained OTR measurements because the amount of dry weight of the coating applied at each different speed was adjusted to approximately 1 g / m². 2 Therefore, performing different coating operations at industrial speeds such as 400-600 m / min will not cause any problems with coating quality or efficiency.

[0131] The OTR measurements of laminated material samples (including metallized coatings) at 80% relative humidity show that the different contributions of different paper types and the possible effects of variations in the metallized coating are leveled out. Oxygen barrier results appear to be at a similarly high level (i.e., similarly low OTR values) due to the synergistic effect between the combination of base coat and barrier pre-coating with the metallized barrier coating. Some differences in water vapor transmission rate values ​​are noted, believed to be due to variations in the quality and thickness of the metallized barrier coating in different laminated material structures. By comparing the OTR values ​​of laminated samples with and without a metallized barrier coating on a pre-coated paper substrate at 80% relative humidity (a more realistic environment for filled liquid food carton packaging containers), the oxygen barrier performance of laminated packaging materials with a specific combination of base coat, barrier pre-coating, and barrier deposit coating is improved by 4-5 times.

[0132] For the formation, filling, and sealing of the filled packages, the laminated packaging materials, such as those produced in the configuration of sample 2.3 in Table 2, were further evaluated in limited filling machine tests. No major issues were found regarding packaging integrity (i.e., the relationship between packaging seal and the surrounding environment) and sealing performance during the tests, and the tests were therefore considered successful.

[0133] Furthermore, similar barrier paper laminate structures were evaluated in the same tests, differing only in that they featured a pre-formed polyethylene blown film on the inner side, comprising at least one partial layer of linear low-density polyethylene (LLDPE), thus forming the innermost heat-sealable layer applied to the inside of the barrier-coated paper. Based on the results and observations of the evaluation tests, it can be concluded that laminate configurations with this pre-formed heat-sealable film on the inner side will contribute to further improving the robustness of laminated packaging materials.

[0134] In addition, regarding the attached diagram:

[0135] exist Figure 1 The image shows a cross-section of an embodiment of the paper substrate 10 coated with a barrier layer according to the present invention. The paper substrate 11 has a basis weight of 38 g / m³. 2 "Oil-resistant" paper types (such as Nordic Paper's Super Perga WS Plus) are made with starch from Avebe. The first base layer pre-coating 12 was applied by aqueous dispersion coating and then heated and dried to evaporate the water. The dry weight of the starch base layer pre-coating is approximately 1 g / m³. 2Furthermore, the paper substrate has PVOH from Kuraray applied to the surface of the first base layer coating. The second barrier pre-coating 13 of 6-98. The barrier pre-coating 13 was also applied by aqueous dispersion coating and subsequently heated and dried to evaporate the water. The dry weight of the PVOH barrier pre-coating was approximately 1 g / m³. 2 Furthermore, the paper substrate with the pre-coated barrier layer has an aluminum barrier deposition coating 14, i.e., an aluminum metallization layer, which is applied to the dry surface of the barrier pre-coating 13 by physical vapor deposition with an OD of about 2 and a thickness of about 40 nm.

[0136] exist Figure 2a The image shows a laminated packaging material 20a for liquid carton packaging, wherein the laminated material comprises materials having a flexural strength of 80 mN and a strength of approximately 200 g / m³. 2 The outer layer 21a is a paperboard body layer of paperboard weight, and also includes an outer liquid-tight heat-sealable polyolefin layer 22a applied to the outside of the body layer 21a, facing the outside of the packaging container made of packaging laminate material. Layer 22a is transparent to show outwardly a printed decorative pattern 27a applied to the paper or paperboard body layer, thereby informing consumers of the contents of the packaging, the packaging brand, and other information for retail facilities and food stores. The polyolefin of the outer layer 22a is conventional low-density polyethylene (LDPE) of heat-sealable quality, but may also include other similar polymers, including LLDPE. Its application amount is approximately 12 g / m². 2 The innermost liquid-tight heat-sealable layer 23a is disposed on the opposite side of the main layer 21a, facing the interior of the packaging container made of the packaging laminate material, i.e., layer 23a will be in direct contact with the packaged product. Therefore, this innermost heat-sealable layer 23a forms a strong lateral heat-sealable portion of the liquid packaging container made of the laminated packaging material, comprising a combination of one or more polyethylenes selected from the group consisting of: LDPE, linear low-density polyethylene (LLDPE), and LLDPE (i.e., so-called metallocene-LLDPE (m-LLDPE)) prepared by polymerizing ethylene monomers with C4-C8 (more preferably C6-C8) α-olefin alkylene monomers in the presence of a metallocene catalyst. Its application amount is approximately 22 g / m². 2 .

[0137] The main body layer 21a is laminated to the intermediate low-density polyethylene (LDPE) adhesive layer 26a. Figure 1The uncoated side of the paper substrate 10 (i.e., 25a) with the barrier layer in between. The intermediate adhesive layer 26a is formed by melt-extruding it into a thin polymer melt curtain between two paper rolls, thus laminating the main layer and the paper substrate with the barrier layer together as all three layers pass through the gap of the cooled pressure rolls. The thickness of the intermediate adhesive layer 26a is 12 to 18 μm, for example, 12-15 μm.

[0138] The innermost heat-sealable layer 23a may consist of one or two or more layers of the same or different types of LDPE or LLDPE or blends thereof, and is well adhered to the metallized barrier deposit coating surface 14 of the barrier paper substrate 10 by an intermediate co-extrusion connecting layer, such as ethylene acrylate copolymer (EAA). Thus, when these layers are applied together in a single melt co-extrusion coating step, the innermost heat-sealable layer is bonded to the barrier-coated paper substrate 10.

[0139] exist Figure 2b The diagram illustrates different laminated packaging materials 20b for liquid carton packaging according to the present invention, wherein the laminated material comprises materials having a flexural strength of 80 mN and approximately 200 g / m³. 2 The package includes a cardboard core layer 21b of a certain weight, and also includes an outer liquid-tight heat-sealable polyolefin layer 22b applied to the outside of the core layer 21b, which will point to the outside of the packaging container made of packaging laminate material. The outer polyolefin layer 22b is conventional low-density polyethylene (LDPE) of heat-sealable quality and has been packaged at 12 g / m². 2 The amount applied may include other similar polymers, including LLDPE. The innermost liquid-tight heat-sealable layer 23b is disposed on the opposite side of the main body layer 21b, facing the interior of the packaging container made of the packaging laminate, i.e., layer 23b will directly contact the packaged product. Thus, the innermost heat-sealable layer 23b will form a strong heat-sealable portion of the liquid packaging container made of the laminated packaging material, comprising one or more polyethylenes selected from 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., so-called metallocene-LLDPE (m-LLDPE)).

[0140] The main layer 21b is laminated to the intermediate adhesive layer 26b, which is an adhesive polymer thin layer, by wet lamination. Figure 1The barrier layer is applied to a paper substrate as described herein, which is achieved by applying an aqueous dispersion of polyvinyl acetate adhesive to one of the surfaces to be adhered to each other, followed by pressing them together in a roll gap. This lamination step is performed at industrial speed in an efficient cold lamination or environmental lamination process, without any energy-intensive drying operations to accelerate water evaporation. The dry coating weight of the intermediate adhesive layer 26b is only 3 to 4 g / m². 2 This means that drying and evaporation are not required.

[0141] Therefore, with Figure 2a Compared to conventional melt extrusion laminated polyethylene adhesive layers described herein, the amount of thermoplastic polymer in this laminate can be significantly reduced.

[0142] Alternatively, the innermost heat-sealable liquid-tight layer 23b may consist of a pre-formed blown film comprising any blend of LDPE or LLDPE polymers, and may be laminated to the barrier-coated paper substrate via an intermediate melt extrusion laminated adhesive layer 24b, laminated to the surface of its barrier deposited coating, i.e., the aluminum metallization layer, which comprises a higher... Figure 2a The thicker EAA bonding layer used, or the simpler LDPE adhesive layer, is 12 to 20 μm thick, for example, 12 to 18 μm thick.

[0143] In an alternative embodiment, the pre-formed blown film 23b' is heated at ambient (cold) temperature at a concentration of 3 to 4 g / m³. 2 The content of the acrylic (co)polymer adhesive layer 24b' is used as an aqueous adhesive and is laminated onto the metallized coating through another wet lamination step.

[0144] Another implementation scheme, which possesses all the aforementioned features, is also disclosed herein. Figure 2a The melt-extruded main body laminate 26a, but it is combined with the features of the innermost heat-sealable layer structure 23b', which is applied either by melt extrusion lamination with layer 24b or by wet lamination of pre-formed film 24b', as in combination. Figure 2b As stated above.

[0145] Another implementation plan was also disclosed here, in which... Figure 2b A thin, wet, water-based adhesive dispersion laminate 26a is combined with conventional melt co-extruded inner layers 24a and 23a.

[0146] exist Figure 3a The process of aqueous dispersion coating 30a is shown, which can be used to apply a base pre-coating 12 and a barrier pre-coating 13. Paper substrate roll 31a (e.g.) Figure 1The paper 11) is conveyed to the dispersion coating station 32a, where the aqueous dispersion composition is applied to the top surface of the substrate by rollers. If the surfaces on both sides of the substrate are different, one side is usually more suitable for receiving the coating or printing decorative patterns, and this is the surface to be coated according to the present invention (this side is usually referred to as the top surface or printing surface). Since the dispersion composition has a water content of 80-99% by weight, there is a large amount of moisture on the wet substrate, which needs to be heated and dried to evaporate in order to form a uniform, continuous coating with uniform quality in terms of barrier properties and surface properties (i.e., uniformity and wettability). Drying is carried out by a hot air dryer 33a, which also allows moisture to evaporate and be removed from the substrate surface. The substrate temperature is kept constant at 60 to 80°C as it passes through the dryer. Alternatively, drying can be partially assisted by radiative heat from infrared (IR) lamps combined with hot air convection drying.

[0147] The resulting barrier pre-coated paper substrate roll 34a is conveyed forward to cool and wound onto a reel for intermediate storage, and then the barrier deposition coating 14 is further vapor-deposited onto the barrier pre-coated paper.

[0148] Figure 3b This shows that the main layers 21a and 21b are first laminated to... Figure 1 Paper substrate 10 coated with a barrier layer (i.e., respectively) Figure 2a and 2b Manufactured after 25a or 25b) Figure 2a and 2b The process of the final lamination step of the packaging laminate material 20a or 20b.

[0149] Such as combination Figure 2a and 2b As explained, the main layer paperboard 21a; 21b can be laminated to the barrier layer coated paper substrate 10; 25a; 25b by wet cold dispersion adhesive lamination or by melt extrusion lamination.

[0150] The resulting paper pre-laminated roll 31b is conveyed from an intermediate storage reel or directly from a laminating station used for pre-laminated paper. The non-laminated surface of the main layers 21a; 21b, i.e., its printed surface, is bonded at the cooled roll gap 33 to the molten polymer curtain 32 of the outermost layer 22a; 22b of the laminate material, which is extruded from the extruder feed block and die 32b. Subsequently, the paper pre-laminated roll, now coated on its printed side with the outermost layer 22a; 22b, passes through the second extruder feed block and die 34b and the laminating roll gap 35, where the molten polymer curtain 34 is bonded and coated on the other side of the pre-laminated material, i.e., on the barrier coating surface of the paper substrate 10; 25a; 25b. Therefore, the innermost heat-sealable layer 23a is co-extruded onto the inside of the paper pre-laminated roll to form the final laminated packaging material 36, which is eventually wound onto a storage reel (not shown).

[0151] The two co-extrusion steps at the laminating roll gaps 33 and 35 can alternatively be performed as two consecutive steps in reverse order.

[0152] According to another embodiment, one or both of the outermost layers can be applied in a pre-lamination station, wherein a co-extruded coating is first applied to the outside of the (printed) main paperboard layer or to the metallized coating of the paper substrate coated with a barrier layer, and then the two pre-laminated paper rolls are joined together as described above.

[0153] According to a further embodiment, the innermost layer of the heat-sealable liquid-tight thermoplastic layer is applied in the form of a pre-made film, which is laminated to the coating side of the paper substrate 10 coated with the barrier layer.

[0154] Such as combination Figure 2a and 2b As explained, such an innermost layer 23a; 23 can be laminated onto the paper substrate 10 coated with a barrier layer by wet cold dispersion adhesive lamination or by melt extrusion lamination.

[0155] Figure 4a This is a schematic diagram of an example apparatus for physical vapor deposition (PVD), such as an aluminum metal coating, onto the web substrate of the present invention. A pre-coated paper substrate 44a undergoes continuous evaporation deposition 40 of evaporated aluminum on its pre-coated surface to form an aluminum metallization layer, or alternatively undergoes continuous evaporation deposition 40 of a mixture of oxygen and aluminum vapor to form a deposited alumina coating. The coating thickness is 5 to 100 nm, preferably 10 to 50 nm, thereby forming the barrier-coated paper 43 of the present invention. Aluminum vapor is formed by ion bombardment from an evaporation source of a solid aluminum sheet 41. For the alumina coating, some oxygen may also be injected into the plasma chamber via an inlet.

[0156] Figure 4bThis is a schematic diagram of an example apparatus for plasma-enhanced chemical vapor deposition (PECVD), such as hydrogenated amorphous diamond-like carbon (DLC) coatings, onto the roll substrate of the present invention. In a plasma reaction zone generated in the space between a magnetron electrode 45 and a cooled roll transfer drum 46 (which also serves as an electrode), the roll substrate 44b undergoes continuous PECVD with plasma 50 on one surface while the film is transported by the rotating drum along the circumferential surface of the drum through the plasma reaction zone. The plasma used for depositing amorphous DLC coatings can be generated, for example, by injecting a gaseous precursor composition containing organic hydrocarbon gases (e.g., acetylene or methane) into the plasma reaction chamber. Other gas barrier coatings can be applied using the same primary PECVD method, such as silicon oxide coatings (SiO2). x Then, it starts with the precursor gas of organosilicon compounds.

[0157] Figure 5a An embodiment of a packaging container 50a produced using the packaging laminate material according to the invention is shown. This packaging container is particularly suitable for beverages, sauces, soups, etc. Typically, such packaging has a volume of about 100 to 1000 ml. It can be of any structure, but is preferably brick-shaped, with longitudinal and transverse seals 51a and 52a respectively, and optionally has an opening device 53. In another embodiment not shown, the packaging container can be formed into a wedge shape. To obtain such a "wedge shape," only the bottom portion of the packaging is folded, such that the transverse heat seal at the bottom is hidden under triangular flaps, which are folded and sealed at the bottom of the packaging. The top transverse seal remains unfolded. In this way, the partially folded packaging container is still easy to handle and dimensionally stable enough to be placed on a food store shelf or any flat surface.

[0158] Figure 5b An alternative example of a packaging container 50b produced using the alternative packaging laminate according to the invention is shown. This alternative packaging laminate is thinner due to its thinner paper body layer, so it is not dimensionally stable enough to form a parallelepiped or wedge-shaped packaging container, and it is not folded into shape after the transverse seal 52b. This packaging container will remain a pillow-shaped bag container and will be dispensed and sold in this form.

[0159] Figure 5c A hilltop-shaped package 50c is shown, which is formed by folding pre-cut stock or blanks into a laminated packaging material comprising a cardboard body layer and a paper substrate coated with a barrier layer according to the present invention. A flat-top package can also be made from similar stock.

[0160] Figure 5dA bottle-shaped package 50d is shown, which is a combination of a sleeve 54 and a top 55 formed from a pre-cut blank of the laminated packaging material of the present invention. The top is formed by injection-molded plastic and an opening device (such as a screw cap). This type of packaging is exemplified by products under the trade name Tetra. and Tetra Sales. These specific packages are formed by attaching a molded top 55 with an opening device in the closed position to a tubular sleeve 54 of laminated packaging material, sterilizing the resulting bottle top capsule, filling it with food, and finally folding it to form the bottom of the package and sealing it.

[0161] Figure 6 The principle described in the introduction of this application is illustrated, wherein a roll of packaging material is formed into a tube 61 by overlapping the longitudinal edges 62, 62' of the roll and heat-sealing them together to form an overlap joint 63. The tube is continuously filled 64 with liquid food to be filled, and the tube is divided into individual filled packages by repeating double transverse seals 65 below the horizontal plane of the contents filled in the tube and spaced a predetermined distance from each other. Packages 66 are separated by cutting between the double transverse seals (top seal and bottom seal) and are ultimately shaped into the desired geometry by folding along pre-prepared crease lines in the material.

[0162] In conclusion, the present invention is not limited to the embodiments shown and described above, but can be varied within the scope of the claims.

Claims

1. A cellulose-based substrate (10) coated with a barrier layer, used as a barrier sheet in laminated packaging materials for liquid foods, comprising: Cellulose-based substrate (11); A barrier pre-coating (13) is applied to the first side of the cellulose-based substrate. The barrier pre-coating (13) consists of a polymer selected from the group consisting of ethylene alcohol polymers and ethylene alcohol copolymers, and optional additives, applied by dispersion coating or solution coating at a concentration of 0.5 to 2 g / m. 2 The amount of the barrier layer is applied; and a barrier deposition coating (14) is further applied to the barrier pre-coating, the barrier deposition coating being applied by a vapor deposition method, wherein the cellulose-based substrate (10) coated with the barrier layer also includes a base pre-coating (12), the base pre-coating (12) being different from the barrier pre-coating (13) and composed of a polymer selected from the group consisting of starch, modified starch and cellulose ether, and is applied to the cellulose-based substrate (11) by dispersion coating or solution coating, and is thus positioned adjacent to and in contact with the first side of the cellulose-based substrate layer, and positioned below the barrier pre-coating, the cellulose-based substrate coated with the barrier layer being suitable for providing gas and water vapor barrier properties in laminated packaging materials and packaging made therefrom.

2. The cellulose-based substrate (10) coated with a barrier layer according to claim 1, wherein the additive is based on an inorganic layered compound in a dry coating weight of 1 to 20% by weight.

3. The cellulose-based substrate (10) coated with a barrier layer according to claim 1, wherein the additive is a polymer or compound having a functional carboxylic acid group.

4. The cellulose-based substrate (10) coated with a barrier layer according to claim 3, wherein the polymer having functional carboxylic acid groups is selected from ethylene acrylic acid copolymer and ethylene methacrylic acid copolymer or mixtures thereof.

5. The cellulose-based substrate (10) coated with a barrier layer according to claim 4, wherein the polymer having functional carboxylic acid groups is an ethylene-acrylic acid copolymer.

6. The cellulose-based substrate (10) coated with a barrier layer according to claim 1, wherein the barrier pre-coating layer (13) comprises a polymer selected from the group consisting of polyvinyl alcohol (PVOH) and ethylene vinyl alcohol (EVOH).

7. The cellulose-based substrate coated with a barrier layer according to any one of claims 1-6, wherein the barrier pre-coating layer (13) has been applied by dispersion coating or solution coating at a dry weight of 0.5 to 1.5 g / m³. 2 The amount applied.

8. The cellulose-based substrate coated with a barrier layer according to any one of claims 1-6, wherein the barrier deposition coating (14) is a vapor-deposited coating of a material selected from the group consisting of metals, metal oxides, inorganic oxides and carbon coatings.

9. The cellulose-based substrate coated with a barrier layer according to any one of claims 1-6, wherein the barrier deposition coating (14) is a vapor-deposited coating selected from the group consisting of aluminum metallization coatings and aluminum oxide AlOx.

10. The cellulose-based substrate coated with a barrier layer according to any one of claims 1-6, wherein the barrier deposition coating (14) is applied to a thickness of 10 to 80 nm.

11. The cellulose-based substrate coated with a barrier layer according to claim 9, wherein the barrier deposition coating (14) is an aluminum metallization coating, which is applied to an optical density OD of 1.8 to 2.

5.

12. The cellulose-based substrate coated with a barrier layer according to any one of claims 1-6, wherein the base layer pre-coating (12) comprises a material selected from the group consisting of starch, modified starch, methylcellulose, ethylcellulose, carboxymethylcellulose CMC, hydroxyethylcellulose HEC, hydroxypropylcellulose HPC, hydroxypropylmethylcellulose HPMC and sodium carboxymethylcellulose NaCMC.

13. The cellulose-based substrate coated with a barrier layer according to any one of claims 1-6, wherein the base pre-coating layer (12) has been applied by aqueous dispersion coating or solution coating at a dry weight of 0.5 to 2 g / m³. 2 The amount applied.

14. The cellulose-based substrate coated with a barrier layer according to any one of claims 1-6, wherein the base pre-coating layer (12) has been applied by aqueous dispersion coating or solution coating at a dry weight of 0.5 to 1.5 g / m³. 2 The amount applied.

15. The cellulose-based substrate coated with a barrier layer according to any one of claims 1-6, wherein the barrier deposition coating (14) is an aluminum metallization coating.

16. A laminated packaging material (20a; 20b) comprising a cellulose-based substrate (10; 25a; 25b) coated with a barrier layer according to any one of claims 1-15, and further comprising a first outermost protective material layer (22a; 22b) and a second innermost liquid-tight heat-sealable material layer (23a; 23b; 23b').

17. The laminated packaging material (20a; 20b) according to claim 16, wherein the second innermost liquid-tight heat-sealable material layer (23a; 23b; 23b') comprises a polyolefin polymer.

18. The laminated packaging material (20a; 20b) according to any one of claims 16-17, further comprising a paper or other cellulose-based material body layer (21a; 21b), wherein the cellulose-based substrate (10; 25a; 25b) coated with the barrier layer is disposed inside the paper body layer between the body layer and the second innermost liquid-tight heat-sealable material layer (23a; 23b; 23b').

19. The laminated packaging material (20a; 20b) according to claim 18, wherein the cellulose-based substrate (10; 25a; 25b) coated with the barrier layer is bonded to the body layer (21a; 21b) by an intermediate adhesive layer (26a; 26b) comprising a composition comprising an adhesive selected from the group consisting of polymers and copolymers of acrylic polymers and copolymers, starch, cellulose and polysaccharide derivatives, vinyl acetate and / or vinyl alcohol polymers and copolymers.

20. The laminated packaging material (20a; 20b) according to claim 17, wherein the second innermost liquid-tight heat-sealable polyolefin layer (23a; 23b; 23b') is a preform containing the same or similar polyolefins to improve the robustness of the mechanical properties of the packaging material.

21. The laminated packaging material (20a; 20b) according to claim 18, wherein the second innermost liquid-tight heat-sealable polyolefin layer (23a; 23b; 23b') is a preform containing the same or similar polyolefins to improve the robustness of the mechanical properties of the packaging material.

22. A packaging container (50a; 50b; 50c; 50d) comprising a laminated packaging material as defined in any one of claims 16-21.

23. A method of manufacturing a cellulose-based substrate (10; 25a; 25b; 44a) coated with a barrier layer according to any one of claims 1-15, comprising: The first step involves providing a cellulose-based substrate as a moving roll in a roll-to-roll system (31a). In the second step, the first dispersion or solution of the base layer precoat composition is dispersed and coated (32a) onto a moving cellulose-based substrate (31a), and then the applied base layer precoat is dried (33a) by forced evaporation. The third step involves dispersing (32a') a second dispersion or solution of a barrier pre-coating composition having a different composition from the base layer pre-coating composition onto a movable cellulose-based substrate (31a') coated with the base layer, followed by forced evaporation drying (33a') of the applied barrier pre-coating. The fourth step involves further depositing (40) a barrier deposition coating onto the pre-coated barrier layer of the moving cellulose-based substrate (43) by a vapor deposition coating operation (41).

24. The method according to claim 23, wherein the base layer pre-coating composition (12) is an aqueous dispersion of a material selected from the group consisting of starch, modified starch, methylcellulose, ethylcellulose, carboxymethylcellulose CMC, hydroxyethylcellulose HEC, hydroxypropylcellulose HPC, hydroxypropylmethylcellulose HPMC and sodium carboxymethylcellulose NaCMC.

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