Barrier-coated fibrous cellulose substrates and laminated packaging materials

Abstract

The present invention relates to a method for producing a barrier-coated cellulose fiber substrate (10a) by dispersion coating of a first gas barrier coating (12), and optionally by subsequent barrier deposition coating (14) by vapor deposition. Furthermore, the invention relates to a heat-sealable laminated packaging material containing the barrier-coated cellulose fiber substrate, and a packaging container manufactured from the laminated packaging material.

Description

[Technical Field]

[0001] The present invention relates to a barrier-coated fibrous cellulose substrate used as an oxygen barrier in laminated packaging materials for oxygen-sensitive products, and to a method for producing the barrier-coated fibrous cellulose substrate. Furthermore, the present invention relates to a heat-sealable laminated packaging material containing the barrier-coated fibrous cellulose substrate, and to a packaging container manufactured from the laminated packaging material. [Background technology]

[0002] Disposable packaging containers for oxygen-sensitive liquids or viscous foods are manufactured from cardboard or paper-based packaging laminates. One such common packaging container is sold under the Tetra Brik Aseptic® brand and is primarily used for aseptic packaging of liquid foods such as milk and fruit juices, and is sold for long-term storage at room temperature. The packaging material in this known packaging container is typically a laminate comprising a base layer made of paper, cardboard, or other cellulosic material, and an outer liquid-tight layer made of thermoplastic resin. To ensure barrier properties against oxygen, especially in aseptic packaging and packaging for milk and fruit juices, the laminate material of these packaging containers usually incorporates at least one additional layer (most commonly aluminum foil).

[0003] On the inside of the laminate, that is, the side facing the food contents filled into the container manufactured from the laminate, there is an innermost layer formed on aluminum foil. This innermost layer may consist of one or more layers of adhesive polymers and / or heat-sealable thermoplastic polymers such as polyolefins. In addition, there is an outermost heat-sealable polymer layer outside the bulk layer.

[0004] Packaging containers are generally manufactured by modern high-speed packaging machines that mold, fill, and seal packages from a web or blank pre-assembled from packaging material. Therefore, packaging containers can be manufactured by continuously forming a tubular web of laminated packaging material. In this process, joints are formed by overlapping and fusing the inner and outer layers of heat-sealable thermoplastic polymer at both longitudinal ends of the web. The tube is continuously filled with the target liquid food, and then divided into individual packages by repeatedly sealing the tube laterally at predetermined intervals below the content level. The packages are separated from the tube by cutting along the laterally sealed sections, and the desired geometric shape, usually a parallelepiped, is given by forming folds along pre-defined fold lines in the packaging material.

[0005] The main advantage of this continuous tube forming, filling, and sealing packaging method is that it enables aseptic packaging because the web can be continuously sterilized immediately before tube forming. In other words, it is a method that efficiently sterilizes the liquid contents being filled and the packaging material itself, producing filled packaging containers under clean conditions, and allows for long-term storage at room temperature without the risk of microbial growth in the filled product. Another important advantage of the Tetra Brik Aseptic® packaging method is, as mentioned above, the ability to perform continuous, high-speed packaging, which has a significant impact on cost efficiency.

[0006] Packaging containers for liquid foods sensitive to quality changes, such as milk and juice, can also be manufactured from the laminated packaging material of the present invention using sheet-like blanks or pre-formed blanks. First, the blanks are assembled from a flat-folded cylindrical blank of the laminated packaging material to form an open cylindrical container, and one of its open ends is closed by folding and heat-sealing a single end panel. The closed container is then filled with the food product (e.g., juice) through its open end, and subsequently closed by further folding and heat-sealing the corresponding single end panel. An example of a packaging container manufactured from sheet-like and cylindrical blanks is the conventional so-called gable-top container. Some containers of this type are equipped with a molded plastic top and / or screw cap.

[0007] The aluminum foil layer in packaging laminates provides far superior gas barrier properties than most other gas barrier materials. Aluminum foil-based packaging laminates, traditionally used for aseptic packaging of liquid foods, remain the most cost-effective packaging materials currently available on the market in terms of performance level.

[0008] Other materials competing with foil-based materials must be cost-effective in terms of raw materials, possess comparable food preservation properties, and have a similarly low level of complexity when processed into finished packaging laminates.

[0009] Efforts to develop non-aluminum foil materials for liquid food carton packaging include a general driving force towards the development of high-performance, multi-barrier pre-fabricated films and sheets that can replace aluminum foil barrier materials in conventional laminated packaging materials, or integrate multiple separate barrier layers within laminated materials, and are adaptable to conventional lamination and manufacturing processes.

[0010] Preferably, such an alternative and environmentally sustainable barrier material is a barrier-coated paper substrate in which an aqueous dispersion coating or vapor deposition coating is applied to a thin paper substrate. Various aqueous dispersion coating processes, vapor deposition coating processes, and material formulations exist for such coatings, and there is a need for a cost-effective barrier material of this "non-foil" type, i.e., non-aluminum foil material, which has improved barrier properties, particularly barrier properties against gases such as oxygen, and, for example, water vapor barrier properties, for laminate packaging materials for liquid food packaging.

[0011] Prior to this, the international patent application publication WO2011 / 003565A1 discloses a non-aluminum foil packaging material including a barrier coating and a metal-deposited kraft paper substrate for induction heating sealing.

[0012] International Patent Application Publication WO2017 / 089508A1 discloses that improved barrier properties can be obtained in similar packaging laminates from metal-deposited paper by selecting a paper substrate that provides optimal properties. Such metal-deposited paper substrates have demonstrated not only improved barrier properties but also improved stability of the metal-deposited layer in induction heat sealing applications.

[0013] European Patent Application Publication EP4008548A1 discloses that in a similar paper substrate, a base coating layer can improve the quality of subsequent gas barrier dispersion coatings and metal deposition.

[0014] International Patent Application Publication WO2022 / 219056A1 discloses a cellulose-based substrate with an additional barrier coating having a higher density, intended for similar laminated packaging materials and packaging containers.

[0015] However, there remains a demand for gas barrier coated paper substrates that are even more advanced than conventional technologies. It is crucial that laminated packaging materials containing such barrier coated substrates maintain sufficient thermal sealing performance even under harsh environmental and extreme climatic conditions. Furthermore, there is a growing demand for improved recyclability and environmental sustainability properties of the materials used in gas barrier coated paper substrates and laminated packaging materials employing them. [Overview of the project] [Problems that the invention aims to solve]

[0016] Therefore, an object of the present invention is to provide an improved barrier-coated cellulosic fiber substrate for lamination into heat-sealable packaging materials.

[0017] Furthermore, an object of the present invention is to provide a barrier-coated cellulose fiber substrate that combines good gas barrier properties with good repulping and recyclability, thereby meeting the future needs for sustainable laminated packaging materials, while also exhibiting good thermal sealing properties even under harsh environmental and extreme climatic conditions.

[0018] Furthermore, a general objective of the present invention is to provide improved heat-sealable laminated packaging materials for oxygen-sensitive products, such as barrier-coated cellulosic fiber substrates for non-foil laminated packaging materials for liquid, fluid, or wet food products. These materials do not contain aluminum foil but possess good gas barrier and other barrier properties, and are therefore suitable for sterile, heat-sealed packaging that can be stored for extended periods at a reasonable cost.

[0019] Accordingly, these objectives can be achieved in accordance with the present invention by a barrier-coated cellulosic fiber substrate as defined in the appended claims, a method for producing a barrier-coated cellulosic fiber substrate, and a laminated packaging material and packaging container comprising a barrier-coated cellulosic substrate. [Means for solving the problem]

[0020] According to a first aspect of the present invention, a barrier-coated cellulose fiber substrate is provided, which can be used as an oxygen barrier in heat-sealable laminated packaging materials for oxygen-sensitive foods such as liquid foods. This substrate has a basis weight of 30-80 g / m². 2 , density 700~900kg / m 3 The barrier-coated fibrous cellulose substrate comprises a first gas barrier coating applied to a first surface of the fibrous cellulose substrate by dispersion or solution coating of an aqueous oxygen barrier composition followed by evaporation drying. The barrier-coated fibrous cellulose substrate further comprises a vapor-resistant base coating comprising 25-96% by weight of inorganic particles and 4-75% by weight of a polymer binder, applied beneath the first gas barrier coating and coated by an aqueous dispersion coating so as to be in direct contact with the first surface of the fibrous cellulose substrate. Thus, the barrier-coated fibrous cellulose substrate provides gas barrier properties in a heat-sealable laminated packaging material.

[0021] Fibrous cellulose substrates are essentially composed of cellulose fibers layered to form a fibrous sheet or paper. This means that there are air-filled voids, pockets, or porosity between the fibers. The relatively low density of fibrous substrates ensures a sufficient level of such unfilled spaces, i.e., porosity, between the fibers within the substrate. Therefore, the term "fibrous" in this invention means that the substrate is porous and has not been densified by compressing the fibers beyond the conventional level of cellulose paper or by filling the pores and spaces with low-molecular-weight materials, including low-molecular-weight cellulose such as microcellulose or nanocellulose. The density of fibrous cellulose substrates is 700-850 kg / m³. 3 More preferably 700-830 kg / m 3 Most preferably 700-800 kg / m 3This relatively low density is achieved by not excessively compressing the cellulose fibers within the substrate and by using cellulose fibers distinct from the fibrils and crystalline variants of microcellulose and nanocellulose, thereby ensuring uniform porosity between the fibers within the substrate. Fibrous cellulose substrates are typically paper.

[0022] The fibrous cellulose substrate may essentially be made from kraft pulp fibers, and is what is known as kraft paper.

[0023] Cellulosic fiber substrates suitable for the present invention are not limited to specific types of paper or cellulose, but include cellulosic substrates based on all types of natural fibrous cellulose. However, the present invention is not applicable to substrates derived from plastics or homogeneous polymers, such as films made from regenerated cellulose, or to non-porous films or cellulose sheets. Cellulosic fiber substrates do not contain low molecular weight cellulose such as microfibril cellulose (MFC), nanofibril cellulose (NFC), or nanocrystalline cellulose (NCC) within their fiber structure. If such low molecular weight cellulose is included, the voids and pores of the fibrous cellulose will be filled, and the structure will be densified, making it impossible to maintain its porosity. For similar reasons, the content of so-called fine powder (cellulose fibers with fibril cellulose still attached) is considered to be quite low, as it may produce a similar densification effect.

[0024] The steam-resistant base coating may contain 30-96% by weight, e.g., 40-96% by weight, e.g., 50-96% by weight, e.g., 55-96% by weight, e.g., 60-96% by weight, e.g., 65-96% by weight, e.g., 70-96% by weight of inorganic particles, 4-70% by weight, e.g., 4-60% by weight, e.g., 4-50% by weight, e.g., 4-45% by weight, e.g., 4-40% by weight, e.g., 4-35% by weight, e.g., 4-30% by weight of a polymer binder, and other additives. Thus, this steam-resistant coating is a so-called clay coat or pigment coating, and aims to provide a smooth, dense, and flexible surface applied to a fibrous cellulose substrate. This surface resists the expansion of water vapor trapped in air pockets of the fibrous cellulose substrate, while simultaneously providing an optimal surface for coating a further gas barrier layer, and overall provides good oxygen barrier properties in the packaging container. In other words, even after the laminated packaging material containing a cellulose fiber base material with a barrier coating has been folded and heat-sealed into a packaging container, it maintains good oxygen barrier properties.

[0025] The inorganic particles or fillers may include various inorganic particles such as clay minerals, silica particles, talc, and calcium carbonate. The dispersed and dried base coating layer can function not only as a barrier against the movement of low molecular weight substances such as water vapor, but can also function more efficiently as a load-bearing barrier that resists the rapid expansion of water vapor generated from the adjacent fibrous cellulose substrate layer toward the steam-resistant base coating layer, i.e., the rupture of steam blisters.

[0026] In one embodiment, the inorganic particles include layered silicate particles, which further contribute to the barrier properties of the material by forming overlapping mineral flakes or lamellae, thereby preventing the movement of small molecules through the material. Such layered inorganic particles may be selected from clays such as kaolin clay or bentonite clay, silicates, or talc particles.

[0027] The polymer binder of the steam-resistant coating may be an aqueous emulsion of an acrylic or methacrylic homopolymer or copolymer, such as a styrene-acrylate latex, a vinyl-acrylic copolymer latex, or a vinyl acetate-acrylate copolymer latex, and an aqueous emulsion of a styrene-butadiene copolymer, such as a styrene-butadiene latex, and a bio-based emulsion binder, such as a modified starch latex, and an aqueous emulsion of a vinyl alcohol polymer, such as polyvinyl alcohol (PVOH) or ethylene vinyl alcohol (EVOH), and other modified starch or starch derivative aqueous emulsions, which may be an aqueous emulsion binder selected from the group.

[0028] The steam-resistant base coating may be applied by an aqueous dispersion coating and is 5 to 25 g / m in dry weight 2 , for example, 7 to 22 g / m 2 , for example, 7 to 20 g / m 2 , for example, 7 to 19 g / m 2 , for example, 10 to 20 g / m 2 , for example, 10 to 19 g / m 2 is.

[0029] After the dispersion coating of the steam-resistant coating and drying, the coated surface of the base-coated fibrous cellulose substrate is smoothed and compressed by soft calendering or the like to obtain optimal surface characteristics for further coating with a gas barrier material, that is, smoothness and low porosity.

[0030] The dried and uncoated free surface of the steam-resistant base coating after soft calendering has, by measurement, a surface roughness of less than 150 ml / min Bendtsen, e.g., less than 100 ml / min Bendtsen, e.g., less than 80 ml / min Bendtsen, e.g., less than 50 ml / min Bendtsen. Preferably, the surface roughness is very low, and when measured according to ISO 8791-4 (PPS), values ​​of less than 3 μm, e.g., less than 2.5 μm, e.g., less than 2 μm, e.g., 1.5 μm or less, e.g., 1.2 μm or less, e.g., 1.0 μm or less can be measured.

[0031] Furthermore, the inherent flexibility of the steam-resistant base coating allows a subsequently applied, less flexible barrier coating to maintain its cohesiveness and adhesion even when the fibrous cellulose substrate with the barrier coating is bent.

[0032] The fibrous cellulose substrate may further have a second steam-resistant base coating on its opposite side, which may be of the same type as the steam-resistant base coating layer that is a pre-coating on the first surface of the substrate.

[0033] The first gas barrier coating is a dispersion coating layer of an aqueous oxygen barrier composition. That is, it is applied by coating with an aqueous dispersion or solution.

[0034] The aqueous oxygen barrier composition may contain polymers selected from the group consisting of vinyl alcohol polymers and copolymers, for example, the group consisting of polyvinyl alcohol (PVOH) and ethylene vinyl alcohol (EVOH), or polymers selected from the group consisting of starch and starch derivatives, xylan, xylan derivatives, nanofibril cellulose / microfibril cellulose (NFC / MFC), and blends of two or more of these.

[0035] In further embodiments, the aqueous oxygen barrier composition of the first gas barrier coating comprises starch and 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), and starch.

[0036] In yet another embodiment, the aqueous oxygen barrier composition of the first gas barrier coating comprises a polymer selected from vinyl alcohol polymers and copolymers, for example, a polymer selected from polyvinyl alcohol (PVOH) and ethylene vinyl alcohol (EVOH).

[0037] The first gas barrier coating is applied by aqueous dispersion or solution coating, with a total application amount of 0.5 to 4 g / m² by dry weight. 2 For example, 0.5~3g / m 2 For example, 0.5~2g / m 2 It may be applied in this manner. Lower application amounts are insufficient to provide gas barrier properties, while higher application amounts make the coating brittle and prone to cracking during bending and molding of the substrate and laminated packaging material.

[0038] The barrier-coated cellulose fiber substrate may further include at least one additional gas barrier coating applied on the first gas barrier coating. This at least one additional gas barrier coating includes at least one barrier deposition coating applied by vapor deposition, and the barrier-coated fibrous cellulose substrate thus provides gas and water vapor barrier properties in a heat-sealable laminated packaging material. The at least one additional gas barrier coating includes the at least one barrier deposition coating and is coated by vapor deposition, but may also include a further dispersion coating of an aqueous barrier composition that can be applied by dispersion coating or solution coating before or after the barrier vapor deposition coating.

[0039] The barrier deposition coating can be a vapor-deposited coating of a material selected from metals, metal oxides, inorganic oxides, and carbons, such as aluminum, aluminum oxide, silicon oxide, and diamond-like carbon. In one embodiment, the barrier deposition coating is a vapor-deposited coating selected from the group consisting of aluminum and aluminum oxide (AlOx), and is preferably an aluminum vapor-deposited coating. The aluminum vapor-deposited coating, or a combination of aluminum and aluminum oxide coatings, not only provides oxygen and water vapor barrier properties to the heat-sealable laminated packaging material, but also provides barrier properties against light incident from outside the packaging.

[0040] In a second aspect of the present invention, the barrier-coated cellulose fiber substrate of the first aspect may be used in a heat-sealable laminated packaging material. This laminated packaging material may further include a first outermost protective material layer, such as a liquid-tight material layer, and a second innermost heat-sealable material layer. This second innermost heat-sealable material layer forms a contact layer with the product to be packaged in a packaging container formed from the laminated packaging material, and is heat-sealable to itself or to other thermoplastic materials.

[0041] The laminated packaging material may further comprise an additional layer of paper, cardboard, or other cellulose-based material that constitutes a bulk layer, i.e., the main thickness layer, within the laminate.

[0042] A heat-sealable laminated packaging material is provided for heat-sealable carton packaging of oxygen-sensitive food products such as liquids, fluids, or wet foods, further comprising a base layer of paper, cardboard, or other cellulosic material, a first outermost protective material layer which is a liquid-tight material layer, a second innermost layer which is a liquid-tight and heat-sealable material layer, and a barrier-coated cellulosic fiber base material of the first embodiment. This cellulosic fiber base material is placed inside the bulk layer, i.e., between the bulk layer and the second innermost heat-sealable material layer.

[0043] In another embodiment, the heat-sealable laminated packaging material has an inner polymer multilayer corresponding to all polymer layers applied inside a barrier-coated cellulosic fiber substrate, and includes a second innermost liquid-tight, heat-sealable material layer that is in direct contact with the product to be filled into a packaging container manufactured from the packaging material, and a load-bearing layer in the middle that consists of an inner polymer multilayer extruded and coated inside the barrier-coated cellulosic fiber substrate, comprising high-density polyethylene (HDPE), medium-density polyethylene (MDPE), or linear low-density polyethylene (LLDPE) with an MFR of 4-20 g / 10 min (190°C / 2.16 kg) and a melting point above 115°C. The second innermost layer, a liquid-tight and heat-sealable material layer, contains low-density polyethylene selected from the group consisting of low-density polyethylene, LDPE, linear low-density polyethylene, LLDPE, and blends thereof.

[0044] Preferably, the main melting point Tm of the second innermost liquid-tight and heat-sealable material layer is 88 to 110°C.

[0045] The intermediate load-bearing layer may comprise a polymer blend composition containing 30-90% by weight of HDPE or MDPE and 10-70% by weight of LDPE, preferably comprising 50-80% by weight of HDPE or MDPE and 20-50% by weight of LDPE.

[0046] The intermediate load-bearing layer may instead contain a polymer blend comprising 50-95% by weight of LLDPE with an MFR of 4-20 g / 10 min (190°C / 2.16 kg) and a melting point above 115°C, and 5-50% by weight of HDPE or MDPE.

[0047] In a preferred embodiment, the inner polymer multilayer is coated as separate layers by melt extrusion coating in at least two consecutive steps, and the first melt extrusion coating layer is at least partially solidified before the next melt extrusion layer is coated on top of it.

[0048] The inner polymer multilayer portion may further include a binding layer containing an adhesive polymer that is adjacent to and in contact with the barrier-coated inner surface of the cellulose fiber substrate.

[0049] The basis weight of the load-bearing layer is 8-25 g / m². 2 For example, 10-25 g / m 2 For example, 12-25 g / m 2 For example, 15-25 g / m 2 For example, 15-20 g / m 2 In a third aspect of the present invention, the heat-sealable laminated packaging material of the second aspect may be used in packaging containers intended for packaging liquids, fluids, or wet foods. Thus, packaging containers are provided which are partially or entirely made from the laminated packaging material.

[0050] A fourth aspect of the present invention provides a method for producing a barrier-coated cellulosic fibrous substrate according to a first aspect. This method comprises a first step of supplying a fibrous cellulose substrate having a machine-glazed or machine-finished surface as a moving web in a roll-to-roll system, A second step involves dispersing a first dispersion composition for a steam-resistant base coating onto a moving fibrous cellulose substrate, and then drying the applied base coating by forced evaporation. The third step involves performing a smoothing treatment, such as soft calendering, on the surface of the base-coated fibrous cellulose substrate obtained from the second step. A fourth step involves dispersing and coating a smoothed base-coated fibrous cellulose substrate with a first gas barrier coating composition using an aqueous second dispersion or solution, and then drying the applied first gas barrier coating by forced evaporation. Optionally, repeat step 4 one or more times. Optionally, a fifth step involves depositing an additional barrier coating by vapor deposition onto the exposed surface of the first gas barrier coating of a gas barrier-coated fibrous cellulose substrate while it is in transit. It is equipped with.

[0051] In alternative modifications of the method of the present invention, the initial method step is instead to supply the base-coated and smoothed fibrous cellulose substrate obtained from the first, second, and third steps as a moving web in a roll-to-roll system, and this initial step is further followed in the same order as the fourth step, and optionally, the same order as the fifth step.

[0052] The steam-resistant substrate coating composition may be an aqueous composition containing 10-20% by weight of a polymer binder and 80-90% by weight of inorganic particles, based on dry weight.

[0053] The unprocessed free surface of the steam-resistant substrate coating on the fibrous cellulose substrate obtained from the third step has a high level of smoothness, i.e., the surface roughness measured according to ISO 8791-4 (PPS) is less than 3 μm, e.g., less than 2.5 μm, e.g., 2 μm or less, e.g., 1.5 μm or less, e.g., 1.2 μm or less, e.g., 1.0 μm or less. Such a level of smoothness improves the film formation of the gas barrier coating applied thereafter, providing the highest possible gas barrier properties.

[0054] The uncoated free surface of the vapor-resistant base coating on the fibrous cellulose substrate obtained from the second or third step preferably has a Gurley air permeability resistance of 1500 seconds / 100ml or more, for example, 3000 seconds / 100ml or more. This low porosity further improves the film formation of the subsequently applied gas barrier coating, as there is little to no absorption of the oxygen barrier composition liquid into the fibrous molecules on the substrate surface.

[0055] A fifth aspect of the present invention provides a preferred method for producing the heat-sealable laminated packaging material of the second aspect.

[0056] This method, The steps include laminating a barrier-coated cellulose fiber substrate onto a bulk layer of paper, cardboard, or other cellulose material, The steps include: melt-extrude coating a first outermost protective material layer or coating onto the outside of the bulk layer so that it faces outward from the packaging container formed from the laminated packaging material; A step of extruding coating an inner polymer multilayer portion corresponding to all polymer layers laminated inside a barrier-coated cellulose fiber substrate, comprising: a second innermost liquid-tight and heat-sealable material layer that comes into direct contact with the product filled into a packaging container formed from packaging material; and an intermediate load-bearing layer containing high-density polyethylene (HDPE), medium-density polyethylene (MDPE), or linear low-density polyethylene (LLDPE) with an MFR of 4-20 g / 10 min (190°C / 2.16 kg) and a melting point exceeding 115°C, to the inside of a barrier-coated cellulose fiber substrate. The second innermost liquid-tight and heat-sealable material layer comprises low-density polyethylene selected from the group consisting of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and blends thereof. It is equipped with.

[0057] Preferably, the main melting point peak Tm of the second innermost liquid-tight and heat-sealable material layer is 88 to 110°C.

[0058] The intermediate load-bearing layer may also contain a polymer blend composition comprising 30-90% by weight of HDPE or MDPE and 10-70% by weight of LDPE, preferably comprising 50-80% by weight of HDPE or MDPE and 20-50% by weight of LDPE.

[0059] The intermediate load-bearing layer may instead contain a polymer blend comprising 50-95% by weight of LLDPE with a melting point above 115°C and an MFR of 4-20 g / 10 min (190°C / 2.16 kg), and 5-50% by weight of HDPE or MDPE.

[0060] In a preferred embodiment, the inner polymer multilayer is coated as separate layers by melt extrusion coating in at least two consecutive steps, and the first melt extrusion coating layer is at least partially solidified before the next melt extrusion layer is coated on top of it.

[0061] The inner polymer multilayer portion may further include a binding layer containing an adhesive polymer that is adjacent to and in contact with the barrier-coated inner surface of the cellulose fiber substrate.

[0062] In a preferred embodiment, the inner polymer multilayer comprises, in an outside-to-inside order, a binding layer containing an adhesive polymer adjacent to and in contact with the barrier-coated inner surface of a cellulosic fiber substrate; an intermediate load-bearing layer containing high-density polyethylene (HDPE), medium-density polyethylene (MDPE), or linear low-density polyethylene (LLDPE) with an MFR of 4-20 g / 10 min (190°C / 2.16 kg) and a melting temperature exceeding 115°C; and a second innermost liquid-tight and heat-sealing material layer containing low-density polyethylene selected from low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and blends thereof.

[0063] In another embodiment, the inner polymer multilayer portion may be coated as separate layers in at least two consecutive steps by melt extrusion coating. In this case, the first melt extruded coating layer is at least partially solidified before the next melt extruded layer is coated on top of it.

[0064] Traditionally, it has been believed that improving the gas barrier properties of barrier-coated paper can be achieved by adopting a superior cellulose-based substrate, thereby imparting gas barrier properties through lamination with a polymer layer, and / or by increasing the thickness of the barrier coating material, which inherently possesses gas barrier properties. However, it has recently become clear that the interface between the barrier coating and the fibrous cellulose substrate can play a crucial role in optimizing the subsequent coating, which contributes most significantly to the gas barrier properties.

[0065] It has been confirmed that the optimal barrier properties for packaging containers can be achieved by adding a pre-coating of a vapor-resistant base layer containing 25-96% by weight of inorganic particles and 4-75% by weight of polymer binder, placed beneath the first gas barrier coating, and coated by an aqueous dispersion coating so as to be in direct adjacent contact with the first surface of the fibrous cellulose substrate. It is understood that this makes it possible to maintain the same amount of the coated oxygen barrier coating, or even reduce it, even if the barrier properties of the fibrous cellulose substrate itself are not very high. Using such a vapor-resistant base coating results in very good gas barrier properties for the resulting packaging laminate. However, this base coating itself does not impart significant gas barrier properties. That is, oxygen barrier properties are not inherent to the vapor-resistant base coating material. Oxygen barrier properties in folded, filled, and heat-sealed packaging containers are also ensured by the base coating's resistance to the rapid expansion of water vapor, i.e., the base coating's resistance to bursting due to the penetration of vapor bubbles. This ensures a good and robust seal of the filled container during heat sealing, without compromising the integrity of the first gas barrier coating layer and subsequent gas barrier coating layers, and maintaining the seal integrity and lamination integrity of the packaging container without impairment.

[0066] The base coating composition should be selected to provide a flexible substrate and a uniform, dense, and conformable base coating surface for receiving further gas barrier coatings. However, the material selected for the vapor-resistant base coating does not need to contribute to its inherent gas barrier properties.

[0067] The cellulose fiber substrate coated with the barrier coating obtained by the above method improves the gas barrier properties of laminated packaging materials and packaging containers made therefrom. Furthermore, it can improve the recyclability and sustainability properties of the packaging material and packaging containers.

[0068] The term "long-term storage" as used in connection with the present invention means that the packaging container can maintain the quality of the packaged food, i.e., nutritional value, hygienic safety, and taste, 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, under room temperature conditions.

[0069] The term "packaging integrity" generally refers to the airtightness of the packaging, i.e., the resistance of the packaging container to leakage or breakage. This term also encompasses the packaging's resistance to the intrusion of microorganisms such as bacteria, dirt, and other substances that can degrade the filled food and shorten the package's expected shelf life.

[0070] One of the main contributions to the integrity of packaging by laminated packaging materials is the good internal adhesion between adjacent layers of the laminate. Another contribution comes from the material's resistance to defects such as pinholes and breakage within each material layer itself, and yet another from the strength of the sealing joints that seal the material when the packaging container is formed. Therefore, the integrity properties of the laminated packaging material itself generally focus on its ability to withstand thermal and mechanical loads during bending and sealing steps without breaking. More specifically, good adhesion between each laminate is required, as well as high quality of the individual material layers. Regarding the airtightness of the packaging, integrity mainly focuses on the quality of the sealing joints, which is ensured by a robust sealing operation that functions properly in the filling machine. This is further ensured by the appropriate heat-sealing properties of the laminated packaging material.

[0071] The term "liquid or fluid food" generally refers to food products containing fluid contents, and may include food pieces as appropriate. Non-exclusive examples of foods covered include dairy products and milk, soy, rice, grain and seed beverages, juices, nectars, still beverages, water, flavored water, energy drinks, sports drinks, coffee and tea beverages, coconut water, wine, soups, jalapeños, tomatoes, sauces (such as pasta sauces), legumes, and olive oil.

[0072] Furthermore, other examples of oxygen-sensitive foods that can be packaged and protected with the laminated packaging materials of this disclosure include, for example, dry foods and / or foods containing fat, such as powdered milk and other powdered foods. Examples of foods containing fat include cheese, butter, and spreads. Such packaging may be FFS (Form, Fill, Seal) packages such as flow wrap packaging or bags. Alternatively, it may be packaging in the form of bottles, trays, spread containers with lids, extruded tubes, clamshell packaging, sleeves, envelopes, or wrapping paper. In these applications, the packaging materials based on the barrier-coated cellulosic fiber substrate of this disclosure are particularly suitable because the packaging materials are typically subjected to bending and similar stresses (e.g., creasing, stretching).

[0073] In relation to packaging materials and containers, the term "sterilization" refers to a state in which microorganisms have been removed, inactivated, or killed. Examples of microorganisms include bacteria and spores. Generally, a sterilization process is used when products are filled into packaging containers in a sterile state. Needless to say, the integrity characteristics of the packaging are extremely important for maintaining the sterile state of the package during its shelf life. For the long-term storage of filled food products, it is also important that the packaging has barrier properties against gases such as oxygen and water vapor in order to maintain the product's original flavor and nutritional value, such as its vitamin C content.

[0074] The term "bulk layer" typically refers to the thickest or most material-containing layer in a multilayer laminate. That is, it is the layer that contributes most to the mechanical properties and dimensional stability of the laminate, and to the structural stability of the folded packaging container derived from a laminate based on cardboard, paperboard, or carton. It can also refer to the layer that provides a greater thickness distance in a sandwich structure. This layer further interacts with the high-Young's modulus stabilizing opposing layers on either side of the bulk layer to obtain sufficient mechanical properties, such as bending stiffness, to achieve the structural stability of the molded packaging container.

[0075] The term "foil-free" packaging material refers to laminated packaging materials that do not contain aluminum foil with a thickness on the micrometer scale. For example, conventional aluminum foil used for liquid carton packaging is typically 6-9 μm thick. "Foil-free" packaging materials may contain a metal vapor-deposited layer, but the thickness of such a layer, for example, is on the nanometer scale. Because the amount of aluminum material used in such metal vapor deposition is very small, the impact on recycling and utilization of material resources is significantly reduced compared to aluminum foil.

[0076] The term "thermomechanical stability" in relation to a material or material layer means that the material has the ability to maintain its mechanical stability and shape even at high temperatures and during material formation (such as pressing, bending, or heat sealing). This ensures that the vapor-deposited layer is adequately supported by the material or layer and does not deteriorate. Furthermore, the material does not melt or soften even when heated to a predetermined temperature.

[0077] In this specification, “dispersion coating” refers to a coating technique in which an aqueous or substantially aqueous dispersion, suspension, emulsion, or solution of a polymer is applied to the surface of a substrate layer, usually in a continuous web-like form, to form a substantially non-porous solid film after drying. Therefore, the term “dispersion” also includes any suspension, emulsion, solution, or mixture thereof that can provide such a coating after drying. Polyvinyl alcohol (PVOH, PVAL) is a typical polymer suitable for dispersion coating, although at high degrees of saponification, for example, it may actually be a polymer solution or a mixture of dispersed PVOH and dissolved PVOH. The dispersion coating barrier layer or film is formed by dispersion coating, so-called “liquid film coating” technique. Aqueous dispersions may contain fine polymer particles and may therefore be “latex.”

[0078] As used herein, the term “latex” refers to a composition comprising an aqueous suspension, dispersion, or emulsion of polymer particles that are natural polymers, synthetic polymers, biomass-derived synthetic polymers, or combinations thereof.

[0079] The term "polyethylene" refers to a polymer containing approximately 90-100 mole% ethylene monomer. As explained below, there are various types of polyethylene.

[0080] The density of low-density polyethylene (LDPE) is 917-930 kg / m³. 3Typically polymerized from ethylene monomers alone, it has a branched polymer chain structure with long side chains, resulting in a more branched and less dense molecular arrangement, and an overall lower density than medium-density polyethylene (MDPE) or high-density polyethylene (HDPE).

[0081] The term "linear low-density polyethylene" (or LLDPE) includes "Zn-LLDPE" polymerized using a Ziegler-Natta type catalyst, "m-LLDPE" polymerized using a "bound structure" catalyst or "single-site" catalyst, also known as a "metallocene" catalyst, and other linear low-density polyethylenes. Both Zn-LLDPE and m-LLDPE are typically 、 It is produced by copolymerizing ethylene monomer with C4-C8, more preferably C6-C8, α-olefin alkylene monomer. The latter reaction is carried out in the presence of a metallocene catalyst. The comonomer content is usually 1-10 mol%, preferably 8-10 mol%. LLDPE has numerous short-chain branches. It is structurally different from conventional low-density polyethylene (LDPE) in that it does not have long-chain branches. LLDPE polymers usually have a narrower molecular weight distribution than conventional LDPE (particularly noticeable in m-LLDPE), and their properties are also significantly different. The more short-chain branches there are, the lower the degree of crystallinity. This is because crystallization within the polymer is suppressed, and as a result, the density is lower than that of MDPE and HDPE.

[0082] In this application, when "mPE" is referred to, it means a polymer blend for a heat-sealable innermost layer comprising at least 50% by weight of mLLDPE and up to 50% by weight of LDPE, preferably about 70% by weight of mLLDPE and about 30% by weight of LDPE (as related to the drawings, for example).

[0083] Suitable high-density polyethylene (HDPE) and medium-density polyethylene (MDPE) for the inner polymer multilayer portion of the laminated packaging material of the present invention have a density of 930-970 kg / m³. 3In polymers composed of these linear polymer molecules, the comonomer content is typically 2 mol% or less. The absence of long-chain branching is ensured by the selection of an appropriate catalyst (e.g., a Zn catalyst) and reaction conditions.

[0084] MDPE has a moderate density, typically 0.926–0.940 g / cm³. 3 This range is as follows. On the other hand, HDPE has a higher density, typically 0.941–0.965 g / cm³. 3 It is within the range.

[0085] In this specification, the oxygen permeability (OTR) when folded is measured by cutting the laminated material into a standardized circular area sample with a diameter of 104 mm and testing it with a PreSens (Germany) OTR transmission cell equipped with a PSt9 sensor. The cumulative concentration of transmitted oxygen into nitrogen gas is measured by fluorescence measurement over time, and the oxygen permeability is expressed in cm³ for samples that have been pre-adjusted to standard conditions. 3 The sample was plotted over 24 hours. The sample was folded using a high-precision, repetitive folding machine that was mechanized at a speed that induces maximum stress, at an angle of 165 degrees from outside to outside along the fold line in the machine direction (MD), to mimic the conditions of a filling machine. Since each folding operation applies exactly the same stress to the material, the folding tests and subsequent OTR measurements are reproducible and comparable.

[0086] All samples were measured under a temperature and humidity of 23°C and 50% RH on the test gas side, and dry nitrogen on the barrier side. The values ​​were calculated from the oxygen concentration increase gradient. The unit of OTR is the permeation rate per 24 hours of the sample under a 21% oxygen environment, cm³. 3 It is expressed as / sample / 24h.

[0087] The basis weight of the paper substrate is determined in g / m² according to the official test method of ISO 536:2019. 2 Measured in units of μm (m) and kg / m², respectively, according to ISO 534:2011. 3 It was measured in units.

[0088] The thickness of coated polymer layers on paper and in laminated structures can be measured and estimated by taking section samples of the structure and observing them with a scanning electron microscope (SEM). Sectioning may be performed, for example, using a cryomicrotome.

[0089] Surface roughness was measured according to ISO 8791-4.

[0090] The Gurley air permeability resistance was measured according to Tappi T460 om-02.

[0091] We have confirmed that the combination of the vapor-resistant base coating and the gas barrier coating according to the present invention can improve the gas barrier properties of paper substrates to a greater extent than expected. Furthermore, it has become clear that the paper substrate itself does not require any inherent barrier properties.

[0092] For suitability in the final barrier coating step of the vapor deposition process, the fibrous portion of the fibrous paper substrate must be thin and have a low basis weight, preferably 60 g / m², from the viewpoint of efficiency and production economy. 2 For example, 50g / m 2 More preferably 45 g / m 2 The following applies. On the other hand, 30g / m 2 Thinner or lower-basis-weight fibrous cellulose substrates, after coating and drying with a wet dispersion, may exhibit insufficient mechanical strength and / or poor dimensional stability, potentially leading to shrinkage, curling, and even web breakage. Therefore, the basis weight of the cellulose substrate used is preferably 30-70 g / m². 2 For example, 30-65 g / m 2 For example, 35-60 g / m 2 For example, 35-55 g / m 2 That is the case.

[0093] The fibrous cellulose substrate has a density of 900 kg / m². 3 Less than, for example, 850 kg / m³ 3 Less than 800 kg / m 3Because they have relatively low densities, such as less than 1 / 2, they are porous. On the other hand, cellulose fiber substrates must have a dense and smooth surface overall in order to obtain an optimal interface with the oxygen barrier coating applied thereon. This means that fibrous cellulose substrates should not be excessively compressed by high-pressure calendering, hard calendering, supercalendering, etc. Only the surface should be smoothed, which can be done immediately after formation by so-called mechanical glazing or mechanical finishing methods during the drying of the paper in the papermaking step.

[0094] The fibrous cellulose substrate used in the present invention may be formed from cellulose fibers containing at least 50% by dry weight of chemical pulp, such as sulfuric acid pulp or sulfite pulp. The chemical pulp is used to impart toughness to the paper in high-speed coating and processing steps, as well as in final packaging applications.

[0095] Sulfate pulp or "kraft" pulp may be advantageous in terms of improved repulping properties during recycling and general dewatering of fibers.

[0096] For recyclability and good dewatering capacity, cellulose-based fibers may have a Canadian standard filtration efficiency (CSF) of 300 ml or more, e.g., 350 ml or more, e.g., 400 ml or more, as measured according to ISO 5267-2:2001. Correspondingly, cellulose-based fibers may have a Shopper-Leighler (SR) value of less than 40 degrees SR, e.g., less than 36 degrees SR, e.g., less than 32 degrees SR, as measured according to ISO 5267-1:1999.

[0097] Coniferous pulp can be included in the pulp at a concentration of at least 50% by weight to impart strength / toughness properties to the resulting paper. In one embodiment, the cellulosic base material includes at least 50% by weight, for example, 60-100% by weight, for example, 70-100% by weight of kraft cellulose, such as bleached kraft cellulose.

[0098] For specific applications such as liquid-tight packaging of wet, liquid, and viscous fluid products, it has been found that making the cellulose fiber substrate as thin as possible is advantageous. This is because it reduces the amount of polymer required for adjacent liquid-tight and heat-sealing layers. The thickness of the fibrous cellulose substrate with a steam-resistant base coat can be 35-70 μm, for example 35-65 μm, for example 40-60 μm, or for example 40-50 μm.

[0099] In further embodiments, the steam-resistant base coating is an aqueous composition comprising an inorganic filler and a plant-derived polymer binder having intrinsic ductility properties, which may be a latex of one or more of the above-mentioned plant-derived polymer binders selected from the group consisting of starch derivatives, polyisoprene, lignin-based polymers, alginates, gums, and soy-derived proteins.

[0100] The steam-resistant base coating is applied by appropriate dispersion coating techniques such as blade coating, rod coating, bar coating, smooth roll coating, reverse roll coating, lip coating, air knife coating, curtain flow coating, dip coating, and slot die coating, followed by drying by forced convection drying to evaporate the dispersion medium (usually water). Preferably, the steam-resistant base coating is applied by blade coating, roll coating, or rod coating techniques, followed by drying. Therefore, the term aqueous dispersion coating includes coatings of aqueous compositions of binder polymer emulsions, dispersions, suspensions, solutions, and latex formulations, further containing a substantial amount, for example, 50% by weight or more, of pigments, inorganic particles, or other fillers.

[0101] The steam-resistant base coating may include a polymer binder consisting of an aqueous latex composition. Examples include styrene-butadiene latex (SB-latex), methylstyrene-butadiene latex, such as styrene-acrylate latex (SA-latex), vinyl-acrylic copolymers and vinyl acetate-acrylate latex which are acrylate latex, styrene-butadiene-acrylonitrile latex, styrene-acrylate-acrylonitrile latex, styrene-butadiene-acrylate-acrylonitrile latex, styrene-maleic anhydride latex, styrene-acrylate-maleic anhydride latex, mixtures thereof, or plant-derived latex made from plant-derived polymer materials. Furthermore, for example, styrene-acrylate latex and styrene-butadiene latex can have their carbon footprint improved while maintaining similar performance by being at least partially plant-derived.

[0102] In one embodiment, the steam-resistant base coating may contain a polymer binder substantially based on a plant-derived material source by producing an aqueous latex composition containing an emulsion of a plant-derived polymer binder material. This plant-derived polymer binder material includes, for example, starch derivatives including modified starch and cross-linked starch, polyisoprene, lignin-based polymers, gums such as alginates and guar gum, and soy-derived proteins including latex compositions, such as Ecosynthetix's "Ecosphere," Vystar's "Vytex," Stora Enso's "NeoLigno," Organoclick's "OC-Binder," and Polygal's "Polygal" surface coatings. For example, Ecosynthetix's biolatex composition Ecosphere® is an aqueous latex consisting of cross-linked starch particles. The latex may be produced by aqueous emulsion polymerization. Alternatively, as in the case of producing latex from biopolymers, a biopolymer material such as starch may be plasticized under shear force to an appropriate particle size, and then crosslinked by adding a crosslinking agent. Subsequently, the biopolymer particles may be added to an aqueous dispersion to form an aqueous latex or suspension of particles.

[0103] Therefore, the steam-resistant base coating may include an aqueous latex composition comprising a polymer material having intrinsic ductility properties selected from styrene-butadiene copolymer (SB), styrene acrylate copolymer (SA), other acrylate polymers and acrylate copolymers, such as vinyl acrylic copolymer and vinyl acetate acrylate copolymer, as well as an aqueous latex of a plant-derived polymer material.

[0104] In further embodiments, the steam-resistant base coating may include an aqueous latex composition of a plant-derived polymer material having inherent flexibility, selected from the group consisting of starch derivatives including modified starch and cross-linked starch, polyisoprene, lignin-based polymers, alginates, gums, and soy-derived proteins.

[0105] In yet another embodiment, the steam-resistant base coating may include an aqueous latex composition containing cross-linked starch particles.

[0106] The latex composition may further contain inorganic filler particles such as kaolin clay or other layered clay compounds, silica particles, talc particles and / or calcium carbonate in a dry content of 40-96% by weight, e.g., 50-96% by weight, e.g., 60-96% by weight, e.g., 70-96% by weight. The filled coating composition is thought to prevent water vapor bubbles from destroying or eroding any subsequently applied adjacent coating layer, no matter how thin it may be. This is a significant advantage because laminated packaging materials containing barrier-coated cellulosic fiber substrates may be used under high-humidity climatic conditions, thereby loading the paper in the cellulosic fiber layer within the laminate with a high moisture content. Typically, the moisture content of paper at equilibrium under a relative humidity (RH) of 80% is about 12%, and is expected to approach 15% at higher RHs.

[0107] The inclusion of fillers further enhances the flexibility of the vapor-resistant base coating while simultaneously reducing tension within the pre-coating. As a result, the pre-coating follows the cellulose fiber substrate when bent, preventing cracking in the base coating itself or the first gas barrier coating subsequently applied on top of the base coating.

[0108] The steam-resistant base coating may also contain appropriate amounts of additives such as thickeners and crosslinking agents. The amount of these additives is limited to 10% by weight or less of the steam-resistant base coating by dry weight.

[0109] In another embodiment, the steam-resistant base coating may contain, by dry weight, 10-20% by weight of a polymer binder material having inherent flexibility, 75-85% by weight of an inorganic filler, 3-5% by weight of a crosslinking compound such as starch, and 1-2% by weight of a thickener.

[0110] The filler may be an inorganic filler selected from the group consisting of clays such as bentonite clay, kaolin clay, talc, CaCO3, and nanoclay containing silica particles.

[0111] The filler material can be an inorganic layered compound such as bentonite clay or kaolin clay. Particularly suitable layered clay minerals include laponite, kaolinite, dicite, nacrite, halloysite, antegolite, chrysotile, pyrophyllite, montmorillonite, hectorite, saponite, sasonite, sodium tetrasilicate mica, Na teniolite, common mica, margalite, vermiculite, phlogopite, and sansophyllite. A specific type of such nanoclay layered particle is montmorillonite, for example, sodium-exchanged montmorillonite (Na-MMT). Such layered inorganic particles can provide an effective barrier against the intrusion of low molecular weight compounds through interlayer delamination and can also provide excellent resistance to the rapid expansion of water vapor in adjacent layers.

[0112] Therefore, the ash content of cellulosic substrates with a steam-resistant base coat is 15-25% by weight, for example, 15-23% by weight, as measured according to ISO 1762:2019. The same ash content range, i.e., 15-25% by weight, applies to fibrous cellulosic substrates with a gas barrier coat and a base coat.

[0113] The polymer of the vapor-resistant base coating may be selected so that its glass transition temperature is between -30°C and +30°C, for example, between -30°C and +20°C, in order to impart inherent flexibility to the paper substrate to which the base coating is applied.

[0114] The fibrous cellulose substrate may have a second steam-resistant base coating on its opposite side, which may be of the same type as the steam-resistant base coating on the first surface of the substrate. However, it is preferable that the fibrous cellulose substrate has a steam-resistant base coating only on its first surface.

[0115] The vapor-resistant base coating should be applied in direct, adjacent contact with the surface of the fibrous cellulose substrate. The paper allows moisture to diffuse outward through the laminated packaging material, and the vapor-resistant base coating material also allows such water vapor movement, preventing the undesirable condition of moisture being trapped near moisture-sensitive barrier coatings such as PVOH or EVOH. Moisture moving from the liquid food inside the packaging through the material is gradually transported to the outside of the packaging container via the paper layer and cardboard bulk layer of the laminated packaging material. Subsequently, the fibrous cellulose substrate and cardboard bulk layer remove moisture from the first oxygen barrier coating by "breathing," and after reaching equilibrium, maintain a substantially constant moisture content within the gas barrier coating over time.

[0116] Steam-resistant base coatings require further smoothing after application to fibrous cellulose substrates, followed by forced convection drying. Soft calendering can smooth the surface roughness of the steam-resistant base coating surface to less than 3 μm, for example, less than 2.5 μm (PPS), as measured by ISO 8791-4. However, this smoothing treatment is not performed under high line loads, such as 200 kN or less, and even less than 150 kN, and is therefore not a supercalendering treatment. Soft calendering is performed by attaching a flexible and stretchable outer layer to the press rollers, and the anvil roller may be made of hard steel. On the other hand, in hard calender roller nip, both rollers have hard, incompressible surfaces, such as steel.

[0117] Steam-resistant base coating compositions are applied onto substrates by coating equipment. The most suitable systems for dispersion coating of steam-resistant coatings or coating compositions are blade coaters, roll coaters, and rod coaters, which apply large quantities of coating composition to paper and scrape off the excess. Common coating equipment includes jet coaters, roll coaters, and short residence time coating (SDTA) equipment. The advantage of roll coaters is that defects in the substrate paper are less critical to them, making them suitable when thick coatings are desired. The blades used to scrape off excess coating are made of steel and may have ceramic tips to extend their lifespan. After coating, the material typically passes through an IR dryer, hot air dryer, or cylinder dryer.

[0118] The PPS roughness of the first upper surface of the fibrous cellulose substrate with a base coat, as determined by the above test method, is preferably less than 2.5 μm, for example less than 2.2 μm, for example less than 2.0 μm, for example 1.8 μm or less, in order to further improve the gas barrier coating performance.

[0119] When a base-coated fibrous cellulose substrate is further coated with a first gas barrier coating by dispersion coating, the PPS surface roughness, when measured according to TAPPI 555 om-15 equivalent to ISO 8791-44, may be less than 2.5 μm, for example less than 2.2 μm, for example less than 2.0 μm, for example 1.8 μm or less.

[0120] The lower the surface roughness, the more perfect the interface with subsequent adjacent layers or coatings, reducing defects such as pinholes and non-uniformity in the coating layer. As a result, the gas barrier coating and subsequent coating layers can be applied with higher quality, thinner, or both. Therefore, even with the same film thickness of the gas barrier coating, superior oxygen barrier properties can be obtained in the coating itself.

[0121] The flexibility of the vapor-resistant base coating reduces the tendency for the material to crack in the paper by redistributing stress and strain over a larger surface area, for example during folding, and consequently reduces the tendency for crack formation in the gas barrier coating as well.

[0122] The first gas barrier coating that imparts basic gas barrier properties to a cellulose fiber substrate coated with the base coat of the present invention may be an oxygen barrier dispersion coating applied by dispersion coating or solution coating.

[0123] Gas barrier coatings applied by coating an aqueous dispersion or solution of an oxygen barrier composition may possess inherent oxygen barrier properties and may contain polymers that are sustainable in terms of both food safety and recyclability, as well as environmental sustainability in industrial coating and lamination steps. Therefore, such polymers are dispersible and / or water-soluble and may be applied by an aqueous "dispersion coating" process, or a so-called "liquid film coating" process. Non-aqueous or partially aqueous coating compositions, such as those based on alcohol or mixtures of alcohol and water, may also be suitable for achieving the favorable results according to the present invention. However, they are considered less suitable than aqueous coating compositions from an environmental sustainability standpoint.

[0124] In one embodiment, the gas barrier dispersion coating comprises polymers selected from the group including vinyl alcohol polymers and copolymers, such as polyvinyl alcohol (PVOH) and ethylene vinyl alcohol (EVOH), starch, starch derivatives, xylan, xylan derivatives, nanofibril cellulose / microfibril cellulose (NFC / MFC), and blends of two or more of these.

[0125] In another embodiment, the gas barrier dispersion coating is applied by dispersion or solution coating, with a total amount of 0.2 to 6 g / m² by dry weight. 2 For example, 0.5~5g / m2 For example, 0.5~4g / m 2 For example, 0.5~3.5g / m 2 For example, 1-3.5 g / m 2 For example, 1-3 g / m 2 That is the case.

[0126] Suitable processes for coating low-dry-weight gas barrier polymer dispersions / solution compositions include any appropriate wet coating method, such as gravure roll coating, smooth roll coating, reverse roll coating, wire bar coating, blade coating, lip coating, air knife coating, and curtain flow coating. Although the experiments of the present invention were carried out by smooth roller coating, any of the other liquid film coating methods described above that contribute to the formation of a homogeneous layer with a smooth and uniform coating surface are also considered suitable for providing the gas barrier coating of the present invention.

[0127] It is extremely important that the applied coating is uniform, forming a continuous and consistent film on the surface, and free from defects, that is, substantially free from pinholes, blisters, or gaps in the coating. Even very small defects are undesirable as they can adversely affect the barrier properties. In foil-free packaging materials, i.e., materials that do not have thick metal foil that can generally ensure good barrier properties, it is extremely important to minimize defects in very thin and sustainable material coatings. It is advantageous to apply at least two layers of coating overlapping each other to conceal defects in each thin coating layer.

[0128] In a more specific embodiment, the oxygen barrier dispersion coating composition is based on polyvinyl alcohol (PVOH) and ethylene vinyl alcohol (EVOH), which are two of the most common polymers and copolymers suitable for dispersion coatings, namely vinyl alcohol monomers.

[0129] PVOH is preferred as the oxygen barrier polymer. This is because it provides good film-forming properties, gas barrier properties, cost-effectiveness, food compatibility, and odor barrier properties.

[0130] Oxygen barrier compositions based on PVOH exhibit their best performance when the degree of saponification of PVOH is at least 98%, preferably at least 99%, but they also possess oxygen barrier properties even with PVOH that has a low degree of saponification.

[0131] On the other hand, because EVOH is a copolymer containing ethylene monomer units, it has the advantage of imparting a certain degree of moisture resistance to barrier materials. The content of ethylene monomer units depends on the selection of the EVOH grade, but compared to pure PVOH, its presence leads to a decrease in oxygen barrier properties. Conventional EVOH polymers are usually intended for extrusion molding, so the content is typically 3.5 g / m². 2 It is impossible to disperse or dissolve the following thin-film coating barrier films in an aqueous medium. For EVOH to achieve water dispersibility, it must contain a substantial amount of vinyl alcohol monomer units, and its properties should be as close as possible to those of PVOH grade for liquid film coating. Therefore, extruded EVOH layers are not a substitute for liquid film coated EVOH. This is because, compared to extruded EVOH grade, they have inherently lower property similarity to PVOH, and in single-layer coatings by extrusion coating or extrusion lamination, the density is 5 g / m². 2 This is because it is not possible to process the product in a cost-effective quantity below that level.

[0132] Nanocrystalline cellulose (NCC) is a form of nanocellulose, but it is different from fine fibrous cellulose (MFC) or nanofiber cellulose (NFC / CNF).

[0133] Therefore, MFC / NFC may contain longer particles, so-called "fibrils," with a width of 10–1000 nm and a length of at least 1 μm, for example, up to 10 μm, for example, up to 100 μm.

[0134] Both MFC and NFC have an aspect ratio of 50 or higher, while NCC / CNC may be defined as having an aspect ratio of less than 50, for example, in accordance with ISO / TS 20477:2017 and the TAPPI draft standard WI3021.

[0135] The term "NCC" is used for short particles and "rod-shaped" particles with a width of 3 to 100 nm and a length of 100 nm or more (e.g., 100 to 3000 nm, 100 to 1000 nm, 100 to 500 nm). The majority of NCC particles in a composition should have these dimensions, for example, a length of 100 to 200 nm, a small width of 3 to 100 nm, and a length in the range of 100 to 500 nm.

[0136] The oxygen barrier dispersion coating composition may further contain about 1% to about 30% by weight of an inorganic layered compound, such as exfoliated nanoclay particles like bentonite, per dry film weight. Therefore, the barrier layer may contain about 99% to about 80% by weight of a polymer per dry film weight. Additives such as dispersion stabilizers and defoamers can also be added to the oxygen barrier composition, preferably in amounts of about 1% by weight or less per dry film weight. The total dry weight of the composition is preferably 5 to 20% by weight, for example, 7 to 15% by weight.

[0137] Further additives to the barrier pre-coating composition include polymers or compounds having functional carboxylic acid groups to improve the water vapor and oxygen barrier properties of the PVOH coating. Preferably, such functional carboxylic acid polymers are selected from ethylene acrylic acid copolymers (EAA) and ethylene methacrylic acid copolymers (EMAA), or mixtures thereof. In one embodiment, such a barrier layer mixture may consist essentially of PVOH, EAA, and an inorganic layered compound. The EAA copolymer may be present in the barrier layer at about 1-20% by weight of the dry weight of the coating.

[0138] It is believed that further improved oxygen and water vapor barrier properties can be obtained by inducing an esterification reaction between PVOH and EAA at an increased drying temperature. This reaction crosslinks PVOH with hydrophobic EAA polymer chains, incorporating them into the PVOH structure. Crosslinking can also be induced by the presence of polyvalent compounds (e.g., metal compounds such as metal oxides). However, such mixtures are expensive due to the cost of additives and may be undesirable from a recyclability standpoint. Therefore, it is more preferable to use barrier dispersion coatings from pure PVOH or EVOH compositions, although advantageous gas barrier effects may also be obtained with oxygen barrier dispersion coatings containing additional additives as described above.

[0139] Therefore, the barrier dispersion coating has a density of 0.2-5 g / m². 2 For example, 0.2~4 g / m 2 More preferably 0.5 to 4 g / m 2 For example, 0.5~3.5g / m 2 For example, 1-3 g / m 2 It may be applied by dry weight as follows: 0.2 g / m² 2 Below 3.5 g / m², no gas barrier properties are obtained at all. 2 Beyond this point, the high cost of barrier polymers in general and the high energy cost of evaporating the liquid may reduce the cost-effectiveness of coating the packaging laminate. 0.5 g / m 2 With the above steps, a recognizable oxygen barrier property is achieved using PVOH, and a good balance between barrier properties and cost is typically 0.5-3.5 g / m². 2 It can be obtained within the range.

[0140] In one embodiment, the gas barrier dispersion coating may be applied as partial layers in a series of two, three, or four steps with intermediate drying. When applied as two partial layers or a "partial coating," each layer may be 0.2 to 2.5 g / m². 2 Preferably 0.5 to 1.5 g / m 2It is appropriate that it be applied in an amount such that a higher quality total coating layer can be obtained from a smaller amount of liquid oxygen barrier composition. More preferably, the two partial layers each contain 0.5 to 1.5 g / m². 2 It may be applied in that amount.

[0141] As an unexpected improvement to the present invention, the gas barrier dispersion coating is not applied directly to paper or a cellulose-based substrate, but rather a first vapor-resistant base coating having a polymer and material composition different from the gas barrier material composition is applied first to prepare the substrate surface, and then a thin layer of the gas barrier coating is applied directly onto the first vapor-resistant base coating. Due to the properties of the aqueous vapor-resistant base coating composition, a dense and uniform base layer surface for further gas barrier coating is realized, and it is thought that adhesive chemical properties and wettability suitable for subsequent application of polyvinyl alcohol-based gas barrier coatings are obtained. Furthermore, this vapor-resistant base coating appears to have the ability to absorb stress and strain applied to the barrier-coated cellulose-based fiber substrate that is subjected to bending and rough handling when used as a laminated packaging material. Therefore, the gas barrier coating is applied directly on top of the vapor-resistant base coating so as to be in contact with it.

[0142] Cellulosic fiber substrates coated with a base coat and a gas barrier dispersion may have a further gas barrier coating on their first gas barrier coating surface, which is a vapor deposition of a gas barrier material selected from metals, metal oxides, inorganic oxides, and amorphous diamond-like carbon. This vapor deposition coating can be applied by physical vapor deposition (PVD) or chemical vapor deposition (CVD), such as plasma-enhanced chemical vapor deposition (PECVD). More specifically, it is selected from the group consisting of aluminum and aluminum oxide (AlOx). Aluminum vapor deposition is preferred.

[0143] A barrier-coated cellulose fiber substrate may have a gas barrier material coated on its upper surface by vapor deposition to a thickness of, for example, 2 to 80 nm, preferably 2 to 50 nm, and more preferably 2 to 45 nm.

[0144] The vapor-deposited barrier coating, which is ultimately applied to the top layer of the cellulose-based substrate, is applied by physical vapor deposition (PVD) or chemical vapor deposition (CVD), such as plasma-enhanced chemical vapor deposition (PECVD).

[0145] Generally, barrier properties are too poor below 5nm to be useful, and above 200nm, for example above 100nm or above 50nm, the flexibility of the barrier coating decreases depending on the type of deposition material, making it prone to cracking when applied to flexible substrates, and also increasing manufacturing costs.

[0146] Other examples of vapor-deposited coatings include aluminum oxide (AlOx, Al2O3) and silicon oxide (SiOx) coatings. Generally, PVD coatings of these oxides are more brittle and unsuitable for incorporation into lamination packaging materials. On the other hand, metal vapor-deposited layers are an exception; despite being manufactured by PVD, they possess suitable mechanical properties for use as lamination materials.

[0147] Typically, aluminum vapor-deposited layers have a thin surface portion that is essentially made of aluminum oxide, due to the nature of the metal vapor deposition process used.

[0148] In one embodiment, such an aluminum vapor-deposited layer is deposited such that its optical density (OD) is 1.8 to 4, preferably 1.9 to 3.5. If the optical density is less than 1.8, the barrier properties of the vapor-deposited film may be too low. On the other hand, if it exceeds 4, the time required for the deposition process increases, and the thermal load on the substrate during deposition increases, which may reduce the thermal stability of the substrate during the deposition step.

[0149] Optical density is measured during the production step using a densitometer based on the principle of diffuse light transmission (instruments from Macbeth, Tobias, etc.). This device is suitable for measuring the optical density of aluminum-deposited films. Measurement accuracy and reproducibility are high, with approximately ±0.2 OD and ±0.01 OD in the measurement range of 0 to 6.60 OD, respectively. In laboratory measurements, it is also possible to measure the light transmittance across the entire visible light spectrum (380 to 800 nm) using a spectrophotometer. The optical density is calculated from the light transmittance (T) value at 560 nm according to the formula OD = -log10(I1 / I0), and the obtained value has equivalent accuracy (±0.2 OD) and is equivalent to the light transmittance densitometer value.

[0150] Other coatings may be applied by plasma-enhanced chemical vapor deposition (PECVD). In this method, the vapor of the compound is deposited on the substrate under conditions of some degree of oxidation. For example, silicon oxide coatings (SiOx) may also be applied by the PECVD process, and excellent barrier properties can be obtained under specific coating conditions and gas compositions.

[0151] DLC (Diamond-Like Carbon) defines a type of amorphous carbon material (diamond-like carbon) that exhibits some of the typical properties of diamond. Preferably, hydrocarbon gases such as acetylene or methane are injected into the plasma as process gases, and an amorphous hydrogenated carbon barrier layer coating, i.e., DLC, is formed by a PECVD vacuum process. DLC coatings applied by the PECVD method under vacuum exhibit good adhesion to adjacent polymer or adhesive layers that are subsequently laminated in laminated packaging materials. In particular, excellent adhesion to adjacent polymer layers is obtained with respect to polyolefins, especially polyethylene and polyethylene copolymers.

[0152] Therefore, the barrier coating may include a first oxygen barrier dispersion coating that is initially applied to a vapor-resistant base coating by dispersion or solution coating, and a further barrier deposition coating that is subsequently applied to the first gas barrier dispersion coating by vapor deposition.

[0153] The cellulose fiber substrate coated with the gas barrier coating obtained by the above method provides low oxygen permeability and low water vapor permeability even after being laminated onto a heat-sealable laminated packaging material, and then the laminated material is folded, molded, and heat-sealed to form a packaging container.

[0154] The carton-based laminated packaging material for packaging oxygen-sensitive products may include a bulk layer of paper or cardboard, an outermost liquid-tight material layer, a second innermost liquid-tight material layer, and a barrier-coated cellulose fiber substrate of the present invention, positioned inside the bulk layer and between the bulk layer and the second innermost layer, toward the inside of a packaging container formed from the packaging material.

[0155] The bulk layer of paper or cardboard has a thickness of approximately 70 μm to 600 μm and a basis weight of approximately 70 to 500 g / m². 2 Preferably about 200-300 g / m 2 It may be conventional paper or cardboard having appropriate packaging quality.

[0156] For low-cost, aseptic, long-term storage containers and packaging for liquid foods, thin packaging laminates with a thinner paper core can be used. Packaging containers made from such laminates are not folded and resemble pillow-shaped flexible pouches. Paper suitable for such pouch-type packaging typically has a basis weight of approximately 50 to 140 g / m². 2 Preferably about 70 to 120 g / m² 2 Comfortably approximately 70-110 g / m² 2Therefore, since the barrier coating substrate itself in the present invention can impart a certain degree of stability to the laminated material, the paper layer corresponding to the "bulk" layer may be made even thinner, and by interacting with the barrier cellulose-based substrate in a sandwich structure, a laminated packaging material with desired mechanical properties can be produced as a whole.

[0157] Barrier-coated paper or cellulose-based substrates are bonded to a bulk layer via an intermediate adhesive or thermoplastic polymer adhesive layer, thereby bonding the uncoated surface of the barrier-coated cellulose fiber substrate to the bulk layer. The adhesive layer may be a polyolefin layer, particularly a polyolefin copolymer mainly composed of ethylene monomer units, or a blend thereof. The adhesive layer may also be formed by extruding a molten adhesive polymer as a molten layer between the webs, passing the three layers through a lamination roller nip while simultaneously pressing them together and cooling, thereby forming a laminated structure by extrusion lamination and bonding the bulk layer to the barrier-coated cellulose fiber substrate. In molten extrusion lamination, a sufficient amount of molten polymer is required to bond two relatively low-temperature surfaces, and in this example, polyolefins, such as low-density polyethylene, are typically used, usually at 12-20 g / m². 2 In some cases, 12-15 g / m 2 That is the case.

[0158] Other suitable adhesive or bonding layers within the laminated material, such as between the bulk layer or core layer and a barrier-coated cellulose fiber substrate, or between the innermost liquid-tight / heat-sealable layer and a barrier-coated paper substrate, may be adhesive thermoplastic polymers known as modified polyolefins. These are mainly based on LDPE or LLDPE copolymers, or graft copolymers having functional group-containing monomer units such as carboxyl groups or glycidyl groups, for example, (meth)acrylic acid monomers or maleic anhydride (MAH) monomers, such as ethylene acrylic acid copolymer (EAA) or ethylene methacrylic acid copolymer (EMAA), ethylene-glycidyl (meth)acrylate copolymer (EG(M)A), or maleic anhydride (MAH) graft 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).

[0159] Alternatively, the barrier-coated cellulose fiber substrate may be bonded to the bulk layer by wet-coating a dispersion of an aqueous adhesive composition containing an adhesive polymer binder onto one of the web surfaces to be laminated, and then pressing the two paper webs together while passing them through a laminating roller nip, thereby obtaining a laminated structure by wet lamination. The water in the aqueous adhesive composition is absorbed into the fibrous cellulose structure of the two paper layers and partially evaporates over time during the subsequent lamination steps. Therefore, a forced-drying step is not required. The barrier-coated cellulose fiber substrate has a dry weight of 0.5-6 g / m². 2 For example, 1-5 g / m 2 More preferably 1-4 g / m 2The bulk layer may be laminated using the adhesive composition. This composition contains a binder selected from the group consisting of acrylic acid polymers and copolymers, starch, starch derivatives, cellulose derivatives, vinyl acetate polymers and copolymers, vinyl alcohol polymers and copolymers, styrene-acrylic latex or styrene-butadiene latex copolymers, or adhesive biolatex. From the viewpoint of environmental friendliness and sustainability, adhesive binders derived from plants or non-fossil resources are preferred.

[0160] Such minute amounts of adhesive compositions can only be applied by coating with an aqueous dispersion or solution of a polymer binder; due to the nature of the molten layer extrusion process, processing by extrusion coating or extrusion lamination of a single-layer polymer melt is impossible. Since both surfaces of the layers to be bonded are cellulose, such wet lamination is performed by the absorption of an aqueous medium into each cellulose layer, resulting in the formation of a thin, dry adhesive layer at the interface between the two layers.

[0161] Suitable materials for the outermost and innermost liquid-tight layers may be polyolefin-based thermoplastic polymers such as polyethylene or polypropylene homopolymers or copolymers, preferably polyethylene, more preferably low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), single-site catalyst metallocene polyethylene (m-LLDPE), and blends or copolymers thereof. Such thermoplastic polymers also have the advantage of being easily fused to the same or similar polymers and other materials exhibiting thermoplastic behavior, i.e., being heat-sealable. According to one embodiment, the outermost heat-sealable and liquid-tight layer is LDPE, and the innermost heat-sealable and liquid-tight layer may be a blend composition of m-LLDPE and LDPE to obtain optimal lamination and heat-sealing properties.

[0162] The outermost layer may only have a protective function against liquids and contaminants, in which case adhesion between the outer surface and other surfaces or articles, such as opening devices, is performed by additional adhesive or hot melt. The same applies to the second innermost layer in packaging for products with low requirements for sealing strength and airtightness. In packaging for liquids, fluids, viscous fluids, and wet foods, the quality of the packaging container largely depends on the second innermost layer also being heat-sealable in order to produce a stronger, more airtight package and to hold the filled product under all handling and distribution conditions; therefore, both liquid-tightness and heat-sealability may be required for the second innermost layer.

[0163] The same thermoplastic materials described for the outermost and innermost layers, such as polyolefins, particularly polyethylene-based materials, can also be suitable for bonding the adhesive layer within the laminate, i.e., between the bulk layer or core layer, such as paper or cardboard, and the barrier-coated cellulose substrate. Therefore, the thermoplastic adhesive layer may be a polyethylene layer, such as a low-density polyethylene (LDPE) layer.

[0164] The second innermost layer, a liquid-tight and heat-sealable polyolefin layer, may be a pre-fabricated film containing the same or similar polyolefin as described above, in order to improve the robustness of the mechanical properties of the packaging material. Due to the manufacturing process in the blow molding and cast molding steps, and the subsequent film stretching step as needed, such a film will have properties different from those obtained from a (co)extruded coated polyolefin layer. Therefore, such a pre-fabricated polymer film can contribute to further reductions in the mechanical robustness, mechanical strength, and integrity of the laminated packaging material, as well as the barrier properties of the packaging container molded and filled from the laminated packaging material.

[0165] Laminated packaging materials can have improved mechanical robustness by laminating a pre-fabricated polymer film between a barrier-coated cellulose fiber substrate and a second innermost liquid-tight material layer. The pre-fabricated film has a higher degree of orientation of its constituent polymer molecules and therefore possesses different mechanical properties from the same or corresponding polymer layer that is simply extruded, coated, or extruded and laminated. Thus, incorporating such a film into the structure can make the entire laminated material more robust and improve its resistance to rough handling in downstream steps. Such pre-fabricated films can be excluded from material selection because they increase costs in both material procurement and lamination steps. Pre-fabricated films have a wide range of mechanical properties, from biaxially oriented, tough films obtained by processing simple extruded films, to films produced by blow molding with inherent polymer orientations resulting from that step, or films with additional subsequent orientations. Alternatively, simply extruded, coated, or extruded and laminated polymer materials may be used.

[0166] The second innermost layer material, which provides liquid-tight and heat-seal properties, may be a blend of polyolefin, preferably low-density polyethylene (LDPE), and linear low-density polyethylene (m-LLDPE) using a single-site or bound structure catalyst, a so-called metallocene catalyst. This is the polymer most widely used in the innermost layer of packaging today, as it achieves the best balance of liquid-tight and heat-seal properties, resulting in the highest package integrity of heat-sealable packaging containers. By carefully selecting the composition of this layer, the amount of polymer in this layer can be optimized to be as small as possible while producing a strong and reliable product-filled packaging. The polymer composition of the innermost liquid-tight and heat-sealable material layer may have a melting point in the range of 88 to 110°C.

[0167] The second innermost liquid-tight and heat-sealable material layer may be a pre-fabricated polymer film or a film containing a heat-sealable thermoplastic polymer material, and may further include, if necessary, a further layer of material to improve the robustness of the mechanical properties of the laminated packaging material.

[0168] In a more preferred embodiment, the heat-sealable laminated packaging material has an inner polymer multilayer portion inside a barrier-coated cellulose fiber base material, which includes at least a second innermost liquid-tight and heat-sealable material layer that is in direct contact with the product to be filled into a packaging container manufactured from the packaging material. The second innermost liquid-tight and heat-sealable material layer contains low-density polyethylene. This layer is selected from the group consisting of, for example, low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and blends thereof. Furthermore, it includes an intermediate load-bearing layer selected from the group consisting of high-density polyethylene (HDPE), medium-density polyethylene (MDPE), linear low-density polyethylene (LLDPE), or a blend of two or more of these, with a metroflow ratio (MFR) of 4-20 g / 10 min (190°C / 2.16 kg) and a melting point exceeding 115°C. The layers of the inner polymer multilayer are formed by extrusion coating on the inner surface of the barrier-coated cellulose fiber substrate.

[0169] The intermediate load-bearing layer may be adjacent to and in direct contact with the liquid-tight and heat-sealable material layer of the second innermost layer, and its main melting point Tm is 88-110°C.

[0170] The second innermost liquid-tight and heat-sealable material layer may contain a blend containing 50-90% by weight of linear low-density polyethylene (m-LLDPE) and 10-50% by weight of low-density polyethylene (LDPE), obtained by a single-site or bound structure catalyst, i.e., a so-called metallocene catalyst.

[0171] The inner polymer multilayer portion may further include a bonding layer made of an adhesive polymer that is adjacent to and in contact with the barrier-coated inner surface of the cellulose fiber substrate.

[0172] This type of internal polymer multilayer structure offers advantages over incorporating pre-fabricated films into laminated packaging materials, as it provides sufficient reliable load-bearing capacity and robustness to the internal polymer multilayer while keeping resistance to opening, tearing, and puncture forces low, and can be implemented at a lower cost. The discovery that sufficient load-bearing properties can be obtained, thereby properly protecting the barrier-coated paper substrate and maintaining its gas barrier properties, while simultaneously protecting the food product filled in the packaging container from the material, was significant. Until now, the use of expensive pre-fabricated films was considered the best solution, but this was accompanied by problems regarding the ease of opening pre-filled and sealed packaging containers made from laminated materials by consumers, making this a groundbreaking innovation.

[0173] The barrier-coated paper substrate of the present invention is not a high-density, high-cost impregnated paper substrate. Rather, it is a porous, i.e., fibrous, low-density paper substrate, and its fibrous material is easily damaged and deteriorated when bent, which can lead to cracks in the barrier coating layer and adjacent layers.

[0174] Barrier-coated cellulose substrates, so-called "paper barriers," generally present unique challenges. Unlike aluminum foil or barrier-coated polymer films, the interior of paper and cellulose sheet barrier substrates may contain organic matter derived from virgin cellulose fibers. Although cellulose fibers are thoroughly treated with heat and chemical processes during the papermaking step and are therefore as clean as possible, they are not as clean as polymer material layers or the inner layers of inorganic foils and vapor-deposited coatings. The barrier coating applied to the inside of a cellulose sheet is heated during application, drying, and vapor deposition, making it a clean material within the laminated material. Therefore, the barrier coating is of high quality as long as the coating is not damaged, protecting the inside of the packaging container from the cellulose sheet fibers inside the laminated material. However, because the coating is thin compared to aluminum foil with a thickness of 5-10 μm, it is sensitive to external stimuli.

[0175] Conversely, this presents challenges for the inner polymer layer, which is a thermoplastic polymer coated or laminated on top of the barrier coating of the paper barrier. These layers need to protect themselves and the filled food product within the packaging container formed by folding and molding from the laminated material including the paper barrier. The inner polymer layer can be applied as a uniform coating or as a pre-fabricated film and serves multiple purposes. The inner polymer multilayer must be heat-sealable (heat-fusible) at high speed in filling and packaging machines and must maintain a liquid-tight state both internally and externally in the formed packaging container. Furthermore, the inner polymer must prevent the barrier coating from being destroyed during the folding and filling steps, and even if the barrier coating is destroyed, it must maintain good integrity against the transfer of microorganisms to the filled food through the package and packaging material. Adding a thicker, stronger polymer layer is effective to some extent, but such measures conflict with the demand to reduce the use of polymer materials in carton liquid packaging materials for environmental sustainability and the demand that packaging materials be reasonably easy for the end consumer to open.

[0176] Studies using improved cellulose-based barrier materials and barrier substrates have shown that minimizing the "loss" of oxygen barrier properties during the folding and molding of laminates containing barrier materials is crucial. Oxygen barrier loss indicates that thin, delicate barrier coatings are damaged to some extent during the folding and molding process into filled packaging containers. Therefore, measuring and understanding the resulting oxygen permeability of the packaging container (package OTR) is more important than measuring the oxygen permeability (OTR) of the flat material, especially for paper barrier materials. Recent advances, based on improvements to the cellulose-based substrates themselves, have significantly improved package OTR.

[0177] Through the development of packaging laminates made from barrier-coated cellulose-based substrates, it has been confirmed that while conventional designs using co-extruded coatings for inner polymer multilayer structures generally exhibited good oxygen barrier properties, they were insufficient in terms of integrity under harsh conditions, occasionally resulting in defective packaging. Therefore, laminate materials have been further improved to include a pre-fabricated, heat-sealable film as the innermost layer. These pre-fabricated films offer good uniformity and reliability in terms of thickness and quality, and have significantly fewer defects such as pinholes and uneven thickness compared to melt-extruded coating layers. Recently, laminates using LLDPE cast films have been developed. This improves the toughness and excellent integrity of the laminate, at least without adversely affecting the overall material. However, this film is expensive, the lamination process is more difficult, and, while not impossible, the ease of opening is unfortunately significantly reduced. The use of such films represents a second-best option for high-integrity, heat-sealable laminate packaging materials using barrier-coated cellulose-based substrates, given recent developments in co-extruded coated inner polymer layer structures.

[0178] The aforementioned specific examples of lamination aim to add complementary properties to laminate packaging materials when a barrier-coated cellulose fiber substrate is used alone as a gas barrier material in a laminate structure, or when the applied coating provides only some gas barrier properties, or when the coating consists only of a moisture-sensitive gas barrier material. By laminating a barrier-coated cellulose substrate with another polymer film that can impart further moisture resistance or water vapor barrier properties, at least two different barrier materials can interact to provide further enhanced overall barrier properties to the laminated structure. Typical examples of such pre-fabricated films that at least add water vapor barrier properties include metal-deposited films and polymer films containing fillers such as flake-shaped mineral fillers or other fine particles, which help to slow the diffusion of water vapor through the laminated structure. Such enhanced barrier properties can be ensured by providing the necessary adhesive layer between the barrier-coated cellulose fiber substrate and the additional barrier film. This is because the intermediate adhesive layer functions as a "buffer" and an additional "gas or vapor transfer interface" in the laminated structure.

[0179] The liquid-tight layers on the outer and inner surfaces of a laminated structure, as well as the inner laminate layer, do not typically provide inherently high barrier properties against moving gas molecules or small molecules. Their purpose is to directly block liquid water from penetrating the cellulosic substrate or other paper layers. While the liquid barrier layer also prevents to some extent water vapor from penetrating the cellulose and causing it to become wet, it cannot maintain the moisture content of the laminated structure at zero or the low levels of "dry" paper (approximately 7-8% moisture content at 23°C and 50% RH). The moisture content in the laminated materials of liquid-filled packaging containers is usually quite high, and unless additional water vapor barriers such as aluminum foil, metal vapor-deposited layers, other vapor-deposited coatings, inorganic material layers, or other polymer material layers are included, moisture movement through the material will occur.

[0180] The laminated packaging materials described above can provide good integrity when molded into filled packaging containers by offering good adhesion between adjacent layers within the laminated structure, as well as good quality from the barrier coating, the vapor-resistant base coating, and combinations thereof. In particular, for packaging liquids and wet foods, it is important that the interlayer adhesion and oxygen barrier properties within the laminated packaging material are maintained even under wet packaging conditions.

[0181] The packaging container formed from the described laminated packaging material may be partially sealed, filled with liquid or fluid food, and then the packaging material itself may be sealed, optionally in combination with a plastic opening or top packaging part.

[0182] In conclusion, a robust and reliable heat-sealable packaging container for long-term storage of liquid foods can be obtained from a heat-sealable laminate comprising a barrier-coated cellulosic fiber substrate as defined in the claims. This is due to the fact that good oxygen barrier properties are maintained even during the folding step of the packaging material, and that the heat-sealing operation is possible without the risk of vapor bubble formation.

[0183] ( (Description of preferred embodiments) Preferred embodiments of the present invention will be described below with reference to the drawings. [Brief explanation of the drawing]

[0184] [Figure 1a] This figure schematically shows a cross-sectional view of an embodiment of a barrier-coated cellulose fiber substrate according to the present invention. [Figure 1b] This figure schematically shows a cross-sectional view of an embodiment of a barrier-coated cellulose fiber substrate according to the present invention. [Figure 1c] Figure 1b shows a simplified cross-sectional schematic of a packaging laminate containing a barrier-coated cellulosic fiber substrate. [Figure 2a]Figure 1b is a schematic cross-sectional view showing an example of a heat-sealable laminated packaging material exhibiting remarkable flexural rigidity, including a barrier-coated cellulosic fiber substrate. [Figure 2b] Figure 1b is a schematic cross-sectional view showing another example of a heat-sealable laminated packaging material, including a barrier-coated cellulosic fiber substrate. [Figure 2c] Figure 1a is a schematic cross-sectional view showing another embodiment of a heat-sealable laminated packaging material, including a barrier-coated cellulosic fiber substrate. [Figure 2d] Figure 1b shows another embodiment of a heat-sealable laminated packaging material, including a barrier-coated cellulose fiber substrate. [Figure 3a] This diagram schematically illustrates the main methods for dispersing and coating a steam-resistant base coating composition or a gas barrier dispersion coating onto a cellulose-based substrate. [Figure 3b] This diagram schematically illustrates a method for melt-extrude-laminating two material webs together within a laminated roller nip. [Figure 3c] This figure schematically illustrates a method for forming an inner polymer layer (including at least the innermost layer) and the outermost layer of the packaging laminate of the present invention by forming a (co)extruded coating layer of a thermoplastic, heat-sealable, and liquid-tight polymer on a web substrate. [Figure 4a] This figure shows a schematic diagram of a plant that performs physical vapor deposition (PVD) coating on a substrate such as the barrier-coated paper substrate shown in Figure 1a or 1b using a solid metal evaporator. [Figure 4b] This figure shows a schematic diagram of a plant that performs plasma chemical vapor deposition (PECVD) coating using magnetron plasma on a substrate such as the barrier-coated paper substrate shown in Figure 1a or 1b. [Figure 5a] This figure shows a typical example of a packaging container manufactured from a laminated packaging material containing a barrier-coated cellulose fiber substrate according to the present invention. [Figure 5b] This figure shows a typical example of a packaging container manufactured from a laminated packaging material containing a barrier-coated cellulose fiber substrate according to the present invention. [Figure 5c] This figure shows a typical example of a packaging container manufactured from a laminated packaging material containing a barrier-coated cellulose fiber substrate according to the present invention. [Figure 5d] This figure shows a typical example of a packaging container manufactured from a laminated packaging material containing a barrier-coated cellulose fiber substrate according to the present invention. [Figure 6] This diagram illustrates the principle of manufacturing this packaging container from packaging laminate material through continuous roll feeding, filling, and sealing steps. [Figure 7] This is an X-ray tomography image showing a cross-section of a laminate of laminated packaging materials, including comparative materials and a series of laminated packaging materials of the present invention. [Figure 8a] This figure shows the effect of low density and inherently high internal porosity in the fibrous cellulose portion of a barrier-coated paper substrate on the number of defects in a laminated packaging material containing the barrier-coated paper after thermal sealing. [Figure 8b] This figure shows a similar effect to Figure 8a, achieved by enlarging the most effective portion within the low-density region. [Figure 9a] This figure shows the oxygen permeability (package OTR) measurement results of packaging containers made of laminated material according to embodiments with different inner polymer layer configurations. [Figure 9b] This figure shows the oxygen permeability (package OTR) measurement results of packaging containers made of laminated material according to embodiments with different inner polymer layer configurations. [Figure 10a] This figure shows the OTR measurement results after uniaxial bending of the laminated material in an embodiment having a different internal polymer layer configuration. [Figure 10b] This figure shows the OTR measurement results after uniaxial bending of the laminated material in an embodiment having a different internal polymer layer configuration. [Figure 11a]This figure shows the maximum opening force, maximum energy, and total energy required to penetrate a pre-cut laminated straw hole with a paper straw, respectively, for a laminated material of a preferred embodiment having a specific inner polymer layer configuration and a comparative laminated material having a different inner polymer layer configuration. [Figure 11b] This figure shows the maximum opening force, maximum energy, and total energy required to penetrate a pre-cut laminated straw hole with a paper straw, respectively, for a laminated material of a preferred embodiment having a specific inner polymer layer configuration and a comparative laminated material having a different inner polymer layer configuration. [Figure 11c] This figure shows the maximum opening force, maximum energy, and total energy required to penetrate a pre-cut laminated straw hole with a paper straw, respectively, for a laminated material of a preferred embodiment having a specific inner polymer layer configuration and a comparative laminated material having a different inner polymer layer configuration. [Figure 12] This figure shows the effect of different preferred coating configurations of the inner polymer multilayer portion on the OTR in panels of laminated packaging material examples in a planar unfolded state and in a folded state after being folded multiple times uniaxially. [Figure 13] This figure shows further results regarding the effect of different coating configurations of the inner polymer multilayer on the OTR in the flat unfolded state and panels that have undergone multiple uniaxial folding processes of the laminated packaging material examples. [Figure 14a] This figure shows the results of investigating the quality and thickness of the inner polymer multilayer portion after biaxial folding of the same laminated material sample as in the test in Figure 12. [Figure 14b] This figure shows the results of an investigation into the quality and thickness of the inner polymer multilayer portion after biaxial bending of laminated material samples composed of HDPE or LLDPE with an MFR of 4-20 g / 10 min (190°C / 2.16 kg) and a melting temperature exceeding 115°C. [Figure 14c]This figure shows the results of an investigation into the quality and thickness of the inner polymer multilayer portion after biaxial bending of laminated material samples composed of HDPE or LLDPE with an MFR of 4-20 g / 10 min (190°C / 2.16 kg) and a melting temperature exceeding 115°C. [Figure 15a] This figure shows the results of evaluating the quality of the inner polymer multilayer in a flat, unfolded panel using a Fischer HV5 poroscopy, for the same laminated sample material as in Figures 12 and 14a. [Figure 15b] Figure 14b shows the results of evaluating the quality of the inner polymer multilayer in a flat, unfolded panel of the laminated sample material using a Fischer HV5 poroscopy. [Figure 16a] This figure shows the results of evaluating the quality of the inner polymer multilayer in a flat, unfolded panel of another laminated material sample, using a Fischer HV5 poroscopy. [Figure 16b] This figure shows the results of evaluating the quality of the inner polymer multilayer in a flat, unfolded panel of another laminated material sample, using a Fischer HV5 poroscopy. [Figure 17a] This figure shows the results of evaluating the quality of the inner polymer multilayer portion on flat, unfolded panels of further laminated material samples, including comparative material samples, using a Fischer HV5 poroscopy. [Figure 17b] This figure shows the results of evaluating the quality of the inner polymer multilayer portion on flat, unfolded panels of further laminated material samples, including comparative material samples, using a Fischer HV5 poroscopy. [Figure 18] This figure shows the results of investigating the quality of the inner polymer multilayer portion after biaxial bending, using the same sample as in the test in Figure 13. [Modes for carrying out the invention]

[0185] Measurement method OTR Package The oxygen transmission rate (OTR) of the package (filled, empty, dried) was measured at 0.2 atm (oxygen concentration 21% in ambient air) in accordance with ASTM F1307-14. The measurement unit is cm 3 / package / 24h.

[0186] The package is attached to a dedicated holder. The inside of the package is replaced with nitrogen and the outside is exposed to the environment around the measuring instrument. When oxygen permeates from the outside through the package and penetrates into the internal nitrogen carrier gas, that information is sent to an electrolytic sensor. Thereby, the sensor measures the amount of oxygen leaking into the nitrogen gas inside the package.

[0187] OTR in Bend Resistance The OTR in bend resistance is measured with a PreSens (made in Germany) OTR permeation cell equipped with a sensor type PSt9 by cutting the laminated material into circular standardized area samples with a diameter of 104 mm. After adjusting the sample to standard conditions, the cumulative concentration of oxygen permeated into nitrogen gas is measured over time by fluorescence measurement and plotted as the oxygen transmission rate in units of cm 3 / sample / 24h. The bending of the sample was carried out by high-precision repeated bending mechanized at a speed that induces the maximum stress at an angle of 165 degrees from the outside to the outside along the fold line in the machine direction (MD) of the packaging material in order to reproduce the conditions of the filling machine. Since each bending operation applies exactly the same stress to the material, the bending test and the subsequent OTR measurement are reproducible and comparable.

[0188] All samples were measured at 23 °C and 50% RH on the test gas side and under dry nitrogen on the barrier side. The value was calculated from the gradient of the oxygen concentration increase. The unit of the calculated OTR is cm 3 / sample / 24h under the condition of an oxygen concentration of 21%.

[0189] Straw Punching Test for开封性Evaluation The following test method is used to measure the maximum force required to perforate or initially penetrate the membrane of a laminated straw hole, also known as a "PPH," which is a pre-punched hole in cardboard.

[0190] The laminated material under test was provided with one pre-cut laminated straw hole per package unit during the manufacturing and processing steps. Therefore, the bulk layer of paper or cardboard was pre-cut at intervals to obtain one small hole with a diameter of 6 mm, suitable for a straw opening, for each package unit. In the subsequent lamination step, these straw holes were overlaminated, i.e., covered by all other layers of the laminate, to form the laminate used in this test. Within the hole area of ​​the cardboard, the outermost LDPE layer was bonded to the LDPE intermediate adhesive layer, forming a laminated film together with the barrier layer and innermost layer. Using a standard compression tester (Zwick-Roell), the maximum force required to open the film by penetrating with a paper straw with a diameter of approximately 5 mm and a beveled tip was evaluated.

[0191] The tests were conducted near the edge of the PPH cardboard, with the tip direction facing both MD and CD. MD means the inclination direction is perpendicular to the machine direction, and CD means the inclination direction is aligned with the machine direction of the laminated material. The test was conducted on a flat laminated material. A preload of 0.1 N was used. The puncture speed was 200 mm / min. The packaging material and straws were pre-conditioned at 23°C and 50% RH before the test. Paper straws with a diameter of 5 mm were cut to a length of 70 mm for use.

[0192] "Holiday" test in biaxially folded materials Further studies were conducted to investigate the adverse effects of bending, based on the principles of ASTM D5162-21. This type of test is commonly known as the "Holiday test."

[0193] The method described in Part B of ASTM D5162-21 was applied to test a flexible packaging material in which a thin polymer layer was laminated on a conductive layer. When the material was exposed to a high voltage of 0 to 20 kV, voltage breakthrough (dielectric breakdown) occurred at a lower voltage in areas where the material was thin or where there were defects in the polymer coating compared to the surrounding thick, defect-free polymer coating material.

[0194] For each sample, the lowest voltage level at which a "breakthrough" or "contact" occurred was recorded and reported.

[0195] Samples of laminated packaging material were first folded flat 180 degrees in one direction using a standardized method (folding device), with the inner surfaces facing each other. Then, they were folded again 180 degrees perpendicular to the initial fold, while maintaining the same geometric shape. Subsequently, the double-folded regions of the packaging material were studied to determine whether the inner polymer layer was weakened at potential weak points in the folded region due to "thinning" of the polymer layer in the metal-deposited area, i.e., the biaxial folding operation, typically by becoming thinner.

[0196] This method is used to detect weaknesses in the inner polymer layer in any region of the packaging material, and therefore can be applied in regions where the laminated packaging material is double-folded.

[0197] Therefore, this test method was used to evaluate the remaining thickness of the inner polymer layer, and the breakthrough voltage of the polymer layer was correlated with the polymer thickness remaining after biaxial folding before high voltage application.

[0198] Defects in the polymer layer of a flat panel The quality of the polymer layer covering the metal vapor deposition layer inside a barrier-coated cellulose substrate was tested using a device called a "poroscopter," a Fischer HV5 manufactured by Helmut Fischer GmbH (Germany), on a flat unfolded material corresponding to the wall panel of a folded molded packaging container. This device is a portable pore testing apparatus equipped with roller electrodes and capable of continuously varying the test voltage in the range of 0.8 to 5 kV. The dielectric strength of the polymer layer formed on the metal barrier layer or coating in laminated packaging materials is tested under high voltage exposure of 0.8 to 5 kV to predict the integrity of the package in terms of polymer layer quality. Such polymer layers are positioned inside the metal layer in packaging laminates, i.e., facing inward towards the packaging container formed from the laminate. At this location, it is important that the layer quality is good, that is, that it has a uniform thickness throughout the entire area and location of the laminate and meets the specified minimum thickness. The occurrence of minute defects in the polymer layer (e.g., thin areas, spots, or pinholes in the coating) is considered a potential risk under subsequent stress associated with exposure to harsh conditions, and this method may detect them as dielectric breakdown occurring earlier at the location of occurrence than at other locations on the laminate. This test is a modified version of the official standard ASTM D5162-21 and is adapted for testing planar flexible packaging materials. This type of test is commonly called the "Holiday test." Using a Fischer HV5 apparatus, the applied voltage is gradually increased to identify the lowest voltage level at which the laminated packaging material exhibits "breakthrough" or "contact," i.e., the earliest "stress level." The test material is stored under environmental conditions of 0-40°C and 0-60% RH to prevent condensation on the metal surface. The results are reported as the percentage of test packaging samples that showed contact at different voltage levels.

[0199] The basis weight of the paper substrate is determined in g / m² according to the official test method of ISO 536:2019. 2 Measured in units of 3, thickness and density are given in μm (m) and kg / m, respectively, according to ISO 534:2011. 3 It was measured in units.

[0200] The thickness measurement of the coated polymer layer on paper and in the laminated structure can be measured and estimated by taking a sliced sample of the structure and observing it with a SEM microscope. Slicing may be performed using, for example, a cryomicrotome.

[0201] The optical density of the metal deposition is measured in the production step using a densitometer (manufactured by Macbeth, Tobias, etc.) that utilizes the principle of diffused light transmission. This device is suitable for measuring the optical density value of the aluminum deposition film. The measurement accuracy and reproducibility are high, being approximately ±0.2 OD and approximately ±0.01 OD respectively in the measurement range of 0 to 6.60 OD. In laboratory measurements, alternatively, a spectrophotometer can be used to measure the light transmittance across the entire visible light range (380 to 800 nm). The optical density is calculated from the light transmittance value (T, or the ratio of incident light to transmitted light, also called I1 / I0) at 560 nm using the formula OD = -log 10 (I1 / I0), and the obtained value has the same accuracy (±0.2 OD) and is equivalent to the optical transmittance densitometer value.

[0202] The surface roughness is measured according to ISO 8791-4.

[0203] The Gurley air permeability is measured according to Tappi T460om-02.

[0204] experiment 1. heat resistance 1.1 Base coat fibrous cellulose substrate (paper) The base coat paper to be tested was a commercially available machine glazed paper (MG) or machine finished paper (MF) based on bleached kraft cellulose fibers or substantially manufactured from the same fibers, with a smooth and steam-resistant base coat applied to the surface side.

[0205]

Table 1

[0206] 1.2 Base coat substrate with barrier coating Each base-coated paper substrate listed in (Table 1) (including the uncoated, high-density comparison paper) was subjected to a barrier coating according to the method described below.

[0207] The upper surfaces of the base-coated paper substrate and the comparative paper substrate were coated twice in a row using a rod coating method with a 10% by weight solids content aqueous PVOH dispersion of Kuraray's Poval® 6-98. After each coating step, evaporation drying was performed while maintaining the substrate surface temperature at 90°C or below, with a coating rate of approximately 2 g / m² in each step. 2 A dry weight coating is applied, totaling 4g / m². 2 The dry weight of the PVOH was obtained.

[0208] 1.3 Laminated Packaging Materials The PVOH-coated and base-coated paper substrates A-F described above are then applied as an intermediate adhesive layer of approximately 20 g / m² to the uncoated back surface of standard liquid-resistant cardboard quality 80 mN (flexural stiffness) clay-coated cardboard. 2 Conventional low-density polyethylene (LDPE) was used and melt-extruded lamination was performed at 310°C. Both surfaces to be joined were corona-treated immediately before lamination. The gas barrier-coated substrate was further corona-treated, and approximately 35 g / m² of conventional LDPE was applied to the non-laminated, barrier-coated surface on the opposite side. 2 The coating was applied by melt extrusion in the specified quantity.

[0209] Therefore, a paperboard-based packaging material laminate having the following general structure was manufactured: / / Outer layer LDPE 12g / m 2 (Ineos 19N730) / Duplex CLC 80mN, 200g / m 2 , cardboard bulk layer / LDPE 20g / m 2 (Ineos 19N730) Adhesive layer / Paper substrate / Steam-resistant base coat / PVOH coating 2x2 g / m 2 LDPE 35g / m 2 (Ineos 19N730) / /

[0210] The lamination of the materials was carried out using a laboratory-scale laminator. The lamination speed was about 100 m / min.

[0211] The duplex CLC paperboard was a conventional clay-coated paperboard. The barrier-coated surface of the paper substrate was arranged to face inward (corresponding to the inside of the packaging container manufactured from the laminated material) in the laminated structure.

[0212] The comparative sample had the same laminate structure but used a PVOH-coated comparative paper substrate G, and thus the laminate had a comparable layer structure as follows: / / Outer 12 g / m 2 LDPE (Ineos 19N730) / Duplex CLC 80 mN, 200 g / m 2 , Paperboard bulk layer / LDPE 20 g / m 2 (Ineos 19N730) Adhesive layer / High-density comparative paper substrate: 0.98 g / cm 3 / PVOH coating 2 x 2 g / m 2 / LDPE 35 g / m 2 (Ineos 19N730) / /

[0213] The comparative paper substrate G had a high density of 980 kg / m 3 and the oxygen transmission rate was measured using an Oxtran 2 / 21 (Mocon) apparatus by the coulometry sensor method in accordance with ASTM D3985 and ASTM F1927-14 at 23 °C, an oxygen partial pressure of 0.2 atm, and 50% relative humidity. The result was about 30 cm 3 / m 2 , 24 h. Therefore, the comparative paper substrate G itself had a certain inherent oxygen barrier property.

[0214] 1.4 Evaluation of heat resistance and vapor expansion properties For the laminated packaging material samples containing various barrier-coated substrates obtained, the steam resistance by heat exposure was evaluated in a test apparatus. Specifically, the inner surface of the coating of the laminate, that is, the 35 g / m that constitutes the inside of the packaging material 2Hot air at a set temperature of 350°C was applied to the LDPE layer. The heat applied to this innermost LDPE layer during the sterilization and / or heat sealing step in the filling machine can cause blistering defects under typical climatic conditions with high humidity.

[0215] The hot air flow rate was maintained at 125 l / min, the distance from the nozzle opening to the packaging material surface was 4 mm, and the speed of the packaging material web passing through the hot air stream was 425 mm / sec. The temperature of the heated surface was maintained in the range of 100–160°C. These test conditions ensure that a thermal load equivalent to that of a filling machine under at least harsh climatic conditions is achieved.

[0216] As shown in Table 2 below, the inner layer (35 g / m²) was identified by analysis of laminate cross-sectional images taken by X-ray tomography. 2 The number of blister defects in LDPE was reported per 1 cm (i.e., 10 mm, 0.01 m) of laminate cross-section.

[0217] [Table 2]

[0218] The X-ray tomography images shown in Figure 7 illustrate how different laminated materials reacted (or did not react) to blister formation when exposed to hot air. The width / length of the laminated material cross-sections shown in the images was 3 mm (0.003 m).

[0219] The image shows different sample laminates on which the tests were performed, stacked one on top of the other. The thick horizontal white line indicates the printable clay-coated surface of the 80 mN duplex paper layer, which is the paperboard bulk layer of various samples. The thick layer of mixed gray and black represents the fibrous part of the bulk layer of various samples, i.e., fibrous paperboard. The thin paper substrate within each laminated sample can be identified as a thin layer with a mixed color composition (gray and black granular regions) similar to the bulk layer paperboard. The two sheets of paper are laminated to each other by a relatively thin and homogeneous gray LDPE layer. The innermost 35 g / m 2 The LDPE layer can be identified as a relatively thick and homogeneous gray line facing the clay-coated surface of the bulk paperboard of the adjacent sample in each upper layer.

[0220] Counting from the top, first, the state after hot air exposure of the comparative laminate G in (Table 2) can be confirmed. Inside the circle drawn on the innermost LDPE layer of 35 g / m 2 which is horizontal and of a homogeneous gray, variously sized circular blisters formed are clearly shown as dark bubbles, and 26 of them are counted in this 3-mm-long sample.

[0221] Next, in the order of being adjacent and located below in the image, the sample laminates F, E, D, C, B can be confirmed. As described in (Table 2), no blisters were observed in the gray innermost LDPE layer in samples F and B, and only 1 blister per 3 mm was confirmed in sample C. On the other hand, in sample laminates A and D, 2 blisters per 3 mm were confirmed. In sample laminate E, 3 blisters per 3 mm were confirmed.

[0222] Bubble pockets formed inside the fibrous paperboard bulk layer or between this layer and the fibrous paper substrate layer were confirmed in sample laminates F, E, C, but were few in sample laminates B and D. However, no serious damage was observed in the innermost LDPE layer at the top of each laminate in any of the samples of the present invention.

[0223] As is clear from (Table 2), the number of blisters formed in each inner layer per unit length of the laminate cross-section under investigation correlated very well with the density of each fibrous paper substrate used.

[0224] Therefore, the density of the fibrous paper is 800 kg / m³. 3 More than 900kg / m 3 Within this range, an average of 7 blisters occur per 1 cm of cross-sectional length of the laminate. The density is 800 kg / m³. 3 If the density is less than 0.80 or 0.85 g / cm³, an average of one blister occurs per 1 cm length of the laminate cross-section. The relationship between the density of the fibrous paper substrate and the number of blisters in the laminate is shown in the graph, and a clear correlation is observed. As shown in Figures 8a and 8b, when the density is 0.80 or 0.85 g / cm³, 3 Beyond this range, it is even suggested that the number of blister formations may increase exponentially with increasing density. The correlation coefficient r of the plotted curve in Figure 8a. 2 While 0.99 is the r of the plotted curve in Figure 8b 2 It is 0.77.

[0225] These results are consistent with our theory that "in-plane" escape routes are necessary to prevent air pockets present within the fibrous portions of a laminate from rapidly expanding out of the plane by penetrating the solid, homogeneous material layer of polymers or other non-fibrous materials during harsh heating processes such as heat sealing steps or sterilization in filling machines. In laminates intended for filling oxygen-sensitive products or products sensitive to moisture transfer from packaging containers, it is crucial that the functional layers of the laminate (i.e., the layers providing integrity and barrier properties) remain intact along their entire plane. On the other hand, fibrous paper substrate layers present in the laminate as a base material for holding barrier coatings can provide in-plane escape routes for vapors and gases to the extent necessary. To promote and limit the plane penetration of vapors within and through the boundaries of thin fibrous layers, such as relatively low-density paper, it is also necessary to provide a vapor-resistant base coating or layer to resist the rapid expansion of air or water vapor bubbles generated outside the fibrous layer and to prevent air and water vapor from moving to more sensitive and critical functional layers.

[0226] 2. Oxygen permeability of laminated packaging materials Base-coated kraft paper, i.e., kraft paper coated with a mineral-filled latex (so-called clay coat) composition, is referred to as base-coated paper base F in (Table 1) and (Table 2) above (Sappi Innerliner Classic 50g / m²). 2 Apply 0.7 g / m² of aqueous dispersion of PVOH (POVAL® 6 / 98, manufactured by Kuraray Co., Ltd.) to the clay coat (CLC) side of the bat. 2 The coating was applied in four consecutive coating steps, with each coating layer being dried by forced evaporation, to achieve the dry weight. The total dry weight of the PVOH coating was 2.8 g / m². 2 Subsequently, in a coating step using physical vapor deposition (PVD), metal deposition treatment was further performed on the PVOH surface of the substrate coated with PVOH until the optical density (OD) reached approximately 3.5.

[0227] Subsequently, the above laminated paper is applied to the back of a clay-coated general 80mN duplex liquid cardboard at 15g / m². 2 The LDPE was laminated as an intermediate layer by melt extrusion lamination.

[0228] The cardboard has a thickness of 12 g / m² on the opposite outer side. 2 The LDPE was extruded and coated. Finally, with the barrier coating surface of the laminated paper facing inward, an LLDPE film was further laminated by melt co-extrusion lamination. In this process, ethylene acrylic acid copolymer (EAA, 6 g / m²) was used as an intermediate adhesive layer. 2 ) and LDPE (15g / m²) 2 ) was used. The final structure of the formed laminate is as follows: / / Outer layer 12g / m 2 LDPE / Duplex CLC cardboard, 80mN, 200g / m² 2 Bulk layer / LDPE 15g / m 2 Low-density fibrous paper substrate / Steam-resistant base coat approx. 18.5 g / m 2 Clay Coat / PVOH Gas Barrier Coating 4 x 0.7g / m2 / Metal deposition OD 3.5 / EAA 6g / m 2 LDPE 15g / m 2 Pre-manufactured LLDPE film, 18μm thick.

[0229] The oxygen permeability (OTR) of the resulting laminated packaging material was tested before and after folding and compared with that of a comparative laminate. The comparative laminate was made of paper with a paper base material (comparative paper G, density 0.98 g / cm³). 3 It has the same laminated structure except that it lacks a steam-resistant base coat. Furthermore, the total coating weight of PVOH and the optical density of metal deposition in the comparative laminate are slightly lower, namely approximately 1.6 g / m². 2 The PVOH and metal deposition in the paper had an optical density of approximately 2 OD. The intrinsic OTR of comparative paper G, when laminated on an LDPE layer, was approximately 30 cm using Oxtran 2 / 21 (Mocon) based on ASTM F1927-14, under conditions of 23°C and 50% RH. 3 / m 2 The measurement was taken at 0.2 atm over 24 hours. Therefore, the comparative layered structure was as follows: / / Outer layer 12g / m 2 LDPE / Duplex CLC cardboard (80 mN, 200 g / m²) 2 Bulk layer / LDPE 15g / m 2 / Comparison paper (G) / PVOH gas barrier coating 2 x 0.8 g / m 2 / Metal deposition OD approx. 2.0 / EAA 6g / m 2 LDPE 15g / m 2 Pre-manufactured LLDPE film, 18μm

[0230] The test laminate was cut into standardized circular samples with a diameter of 104 mm and tested using a PreSens (Germany) OTR transmission cell (equipped with sensor type PSt9). The cumulative concentration of transmitted oxygen into nitrogen gas was measured over time by fluorescence measurement and expressed as oxygen permeability in cm³. 3The sample was plotted over 24 hours. No complex sample adjustments were required. Sample bending was performed using a high-precision, repetitive bending machine that was mechanized at a speed that induced maximum stress, at a 165-degree angle from outside to outside along the machine direction (MD) fold line, to reproduce the conditions of the filling machine. Since each bending operation applied exactly the same stress to the material, the bending tests and subsequent OTR measurements are reproducible and comparable.

[0231] All samples were measured under conditions where the test gas side was 23°C and 50% relative humidity, and the barrier side was dry nitrogen gas.

[0232] The value was calculated from the gradient of increasing oxygen concentration.

[0233] The unit of the calculated OTR is cm 3 / Sample, 24h, 21% oxygen

[0234] [Table 3]

[0235] From these comparable OTR measurements, it can be concluded that the laminated structures of the present invention and the comparative product have similar oxygen barrier properties in both the planar unfolded state and in laminated samples that have been folded once or several times and subjected to mechanical stress. In the comparative sample, the amount of oxygen barrier material (PVOH dispersion coating and PVD metal deposition) used was slightly less, while its high-density paper substrate (0.97 g / cm²) 3 ) contributed to a certain degree of inherent oxygen barrier properties. Therefore, the overall low oxygen permeability (OTR) value in the barrier laminate of the present invention is thought to be partly due to the large amount of applied barrier material. However, from the results of bending the barrier laminate of the present invention, even if the substrate is low-density paper (0.76 g / cm³), 3Even when using ), it was shown that the oxygen permeability does not dramatically increase after being folded several times. Therefore, it is considered that the barrier laminate of the present invention can achieve an oxygen barrier level equivalent to that of the comparative barrier laminate if supplemented with a certain amount of barrier coating, and has the ability to maintain at least equivalent gas barrier properties even after folding. The comparative barrier laminate was previously developed to maintain barrier properties during folding by using a high-density paper substrate for the barrier coating.

[0236] Furthermore, the following will be explained in relation to the attached drawings:

[0237] Figure 1a shows a cross-section of an embodiment of a cellulose fiber substrate 10a coated with the barrier coating of the present invention. The fibrous cellulose substrate 11 is a paper mainly composed of cellulose fibers derived from kraft pulp, with a basis weight of 35 g / m². 2 , density 800g / m 3 The substrate 11 was less than 18 g / m², and a relatively high-viscosity aqueous dispersion coating agent was used to coat the upper surface with fine pigments. The mixture was then dried to evaporate the moisture and initially form a steam-resistant base coating 12. The dry weight of the applied steam-resistant base coating was approximately 18 g / m². 2 In the following step, the applied and dried pigment film was smoothed by a soft color rendering process.

[0238] Furthermore, a gas barrier coating 13 consisting of a barrier dispersion or solution coating of PVOH (Poval® 6-98, manufactured by Kuraray Co., Ltd.) was applied to the surface of the steam-resistant base coat 12 of the base coat paper substrate. The gas barrier coating 13 is applied by a low-solids content and relatively low-viscosity aqueous dispersion coating, and then dried to evaporate the moisture. Preferably, drying is performed as two consecutive partial coating steps, between the wet coating steps and after the second coating step. The total dry weight of the PVOH barrier dispersion coating is approximately 3 g / m². 2 That is the case.

[0239] Figure 1b shows a cross-section of another embodiment of the cellulose fiber substrate 10b with a barrier coating according to the present invention. The cellulose substrate 11 uses the same paper material as in Figure 1a, and a steam-resistant base coating 12 with the same composition as in Figure 1a is applied with a dry weight of approximately 18 g / m². 2 It is applied as follows. Furthermore, the base-coated paper substrate is coated with a similar first gas barrier coating 13 using a barrier dispersion or solution of PVOH (Poval® 6-98, manufactured by Kuraray Co., Ltd.) on the surface of the steam-resistant base coating 12. The first gas barrier coating 13 is applied by an aqueous dispersion coating, and then dried to evaporate the moisture. Preferably, it is carried out as two consecutive partial coating steps, with a drying step in between the coatings, and drying after the second coating. The total dry weight of the PVOH barrier dispersion coating is approximately 3 g / m². 2 That is the case.

[0240] In this manner, the paper substrate coated with the barrier dispersion coating is further subjected to an aluminum barrier vapor deposition coating 14, which is a barrier coating, i.e., aluminum vapor deposition with an OD of approximately 2, applied to the dry surface of the first gas barrier dispersion coating 13 by a physical vapor deposition method.

[0241] Figure 1c shows a cross-section of an embodiment in which the barrier-coated paper substrate of Figure 1b is further simplified into a laminated packaging material. Specifically, a first outermost protective coating is applied to the outermost surface, preferably with polyolefin, a thermoplastic polymer having liquid-tight and heat-sealing properties, so that this coating 15 forms the outside of the packaging container made of the simple laminated packaging material. Next, a heat-sealing material layer 16, which will be the second innermost layer, is laminated onto the uncoated surface of the metal vapor-deposited layer 14, forming a layer that covers the inside of the packaging container made of the laminated material. The outermost layer 15 and the innermost layer 16 may be made of the same material, preferably a thin layer of polyolefin, most preferably polyethylene. Advantageously, the first outermost layer is a single layer of LDPE, and the second innermost layer is a blend of LDPE and mLLDPE to obtain a strong and highly airtight seal for the heat-sealed packaging container, and the second innermost layer is also heat-sealed itself.

[0242] Figure 2a shows a laminated packaging material 20a for liquid carton packaging of small containers (e.g., for 200-300 ml). This laminated material has a bending strength of 80 mN and a basis weight of approximately 200 g / m². 2 The packaging has a bulk layer 21a, and an outer layer 22a made of liquid-tight and heat-sealable low-density polyethylene is applied to the outside thereof. This outer layer is positioned to face outwards when the packaging container is manufactured from the packaging laminate. The layer 22a is transparent and displays the printed decorative pattern 27a applied to the bulk layer of paper or cardboard on the outside. This conveys information about the contents of the packaging, the packaging brand, and other information to consumers in retail facilities and food stores. The polyethylene of the outer layer 22a is conventional low-density polyethylene (LDPE) of heat-sealable quality, but may also include other similar polymers, including LLDPE. This is approximately 12 g / m² 2 It is applied in an amount of [amount]. The innermost liquid-tight and heat-sealing layer 23a is located on the opposite side of the base layer 21a, i.e., the side facing inward into the packaging container manufactured from the laminated packaging material. Therefore, layer 23a is in direct contact with the packaged product. This innermost heat-sealing layer 23a forms a strong lateral heat seal of the liquid packaging container manufactured from the laminated packaging material and includes one or more polyethylenes selected from LDPE, linear low-density polyethylene (LLDPE), and LLDPE produced by polymerization of ethylene monomer and C4-C8, preferably C6-C8 α-olefin alkylene monomer in the presence of a metallocene catalyst, i.e., metallocene-LLDPE (m-LLDPE). The polyethylene of this innermost layer is about 29 g / m 2 It is applied in the amount specified. Alternatively, the innermost liquid-tight and heat-sealing layer 23a' may be a pre-fabricated LLDPE-based film.

[0243] The bulk layer 21a is laminated onto the uncoated surface (i.e., the surface without the gas barrier coating) of the barrier-coated paper substrate 10b shown in Figure 1b. This is 25a, in which an aluminum barrier vapor deposition coating 14 (i.e., an aluminum vapor deposition layer) is applied to the dry surface of the barrier dispersion coating 13 by physical vapor deposition at an OD of approximately 2, and laminated via an intermediate adhesive layer 26a of low-density polyethylene (LDPE). The intermediate adhesive layer 26a is melt-extruded as a thin polymer melt curtain between two paper webs, thereby laminating the bulk layer and the barrier-coated paper substrate onto each other. During this process, all three layers pass through a cooled press roller nip. The coating amount of the intermediate adhesive layer 26a is 15-20 g / m². 2 That is the case.

[0244] The innermost heat-sealable layer 23a may consist of one layer, or two or more sublayers made of the same or different types of LDPE, LLDPE, or blends thereof, and the aluminum vapor-deposited surface 14 of the barrier-coated paper substrate 10b is coated with, for example, ethylene acrylic acid copolymer (EAA) at a rate of approximately 6 g / m². 2 The intermediate co-extruded bonding layer 24a adheres to the barrier-coated paper substrate 10b. This is achieved by laminating layers 24a and 23a simultaneously in a single melt co-extruded coating step.

[0245] Figure 2b shows another laminated packaging material 20b for liquid carton packaging. This laminated material contains the same paperboard core layer 21b as used in Figure 2a(21a), with a flexural strength of 80 mN and a basis weight of approximately 200 g / m². 2 Furthermore, as shown in Figure 2a, a liquid-tight and heat-seal outer layer 22b made of LDPE is formed on the outside of the base layer 21b. In addition, as described above in Figure 2a, a similar innermost liquid-tight and heat-seal layer 23b is arranged on the opposite side of the bulk layer 21b, and an intermediate layer of approximately 6 g / m² made of, for example, ethylene acrylic acid copolymer (EAA) is used. 2 It has a co-extruded bonding layer 24a.

[0246] The bulk layer 21b is the barrier-coated paper substrate 10 shown in Figure 1b, and is further laminated to 25b, the same as 25a in Figure 2a, via a thin intermediate adhesive layer 26b made of an adhesive polymer, by wet lamination. This intermediate adhesive layer 26b is obtained by applying an aqueous dispersion of polyvinyl acetate adhesive or starch-based adhesive to one of the surfaces to be bonded together, and then pressing them with a roller nip after bonding. This lamination step does not require a drying operation that consumes energy to promote water evaporation, and is carried out as an efficient cold or room-temperature lamination step at industrial speeds. The dry weight of the intermediate adhesive layer 26b after application is only 3-5 g / m². 2 Therefore, drying and evaporation of the adhesive layer are not required. This makes it possible to reduce the amount of thermoplastic polymer in the recycling process, such as relatively thick extruded laminated polyethylene polymers, and improve the repulpingability of the packaging material in the recycling process. The laminate layer 26b that adheres the barrier-coated cellulose fiber substrate 25b to the bulk layer 21b can, as an alternative, be a thin layer of a wet laminate polymer binder obtained by drying a dispersed coated aqueous adhesive composition. Such an adhesive layer is made from a polymer that can be easily redispersed in water, thereby enabling repulping of the cellulose fiber component in the paper carton recycling process.

[0247] Therefore, compared to the adhesive layer of conventional LDPE melt extrusion lamination shown in Figure 2a, the amount of thermoplastic polymer in this laminate layer can be significantly reduced.

[0248] In a further embodiment of either the laminated structure of Figure 2a (not shown) or the laminated structure of Figure 2b (shown), the innermost liquid-tight layer 23a' or 23b' may consist of a pre-fabricated polyolefin film comprising any blend of LDPE or LLDPE polymer, which is laminated to a barrier-coated paper substrate, i.e., the aluminum vapor deposition barrier coating, via an intermediate melt-extruded lamination adhesive layer 24a' or 24b'. This adhesive layer is a thicker EAA bonded layer and / or simply an LDPE adhesive layer than those used in Figure 2a or 2b, at 12-20 g / m². 2 For example, 12-18 g / m 2 It is the thickness.

[0249] Figure 2c shows an alternative method in which a bulk layer 21c is laminated onto the uncoated surface (i.e., the surface without the gas barrier coating) of the barrier-coated paper substrate 10a shown in Figure 1a. This substrate 25c does not have a further vapor-deposited barrier coating 14 by aluminum vapor deposition. The lamination method may be the same as the method described in Figures 2a and 2b. If such gas barrier-coated paper is not further coated with a vapor-deposited water vapor barrier layer, the inside of the barrier-coated paper may be complemented in the laminated packaging material by laminating it onto a pre-fabricated polymer film 28c consisting of a substrate layer 28a and a vapor-deposited gas barrier coating 28b. Therefore, the laminated packaging material 20c has layers of the same type as the layers corresponding to Figures 2a or 2b described above, namely a bulk layer 21c of cardboard, an outermost protective polymer layer 22c, and an inner lamination layer 26c which is either an adhesive layer coated with a wet aqueous dispersion or a melt-extruded lamination adhesive layer of a thermoplastic polymer.

[0250] The pre-fabricated polymer film 28c comprises a polymer film substrate 28a and a vapor-deposited aluminum vapor-deposited and / or aluminum oxide 28b. The pre-fabricated vapor-deposited coated film 28c is then laminated onto a gas barrier coated cellulose substrate 25c via an intermediate adhesive layer 29c, such as a melt-extruded lamination layer. The pre-fabricated polymer film may further include heat-sealable layers 23c and 24c on the innermost surface of the laminated material 20c. Alternatively, after laminating the pre-fabricated film 28c onto cardboard, the inner layers 23c and 24c may be further melt-extruded and coated on the inside of the pre-fabricated film 28c.

[0251] Therefore, this is an alternative means of forming an aluminum vapor deposition or aluminum oxide vapor deposition coating inside the first gas barrier coating to protect the latter from the migration of moisture and water vapor from liquid or wet food fillings.

[0252] Figure 2d shows a further laminated packaging material 20d for liquid carton packaging of small containers (e.g., for 200-400 ml). This laminated material has a flexural strength of 80 mN and a basis weight of approximately 200 g / m². 2 The packaging has a paperboard bulk layer 21d and further comprises a liquid-tight and heat-sealable low-density polyethylene outer layer 22d attached to the outside of the base layer 21d. This outer layer 22d is positioned to face outwards from the packaging container manufactured from the packaging laminate. The layer 22d is transparent and displays the printed decorative pattern 27d applied to the paper or paperboard base layer on the outside, thereby conveying information about the packaging contents, packaging brand, and other information to consumers in retail facilities and food stores. The polyethylene of the outer layer 22d is conventional low-density polyethylene (LDPE) of heat-sealable quality, but may also include other similar polymers, including LLDPE polymer. This is approximately 12 g / m² 2 It will be coated with that amount.

[0253] The innermost liquid-tight and heat-sealing layer 23d is positioned on the opposite side of the bulk layer 21d, i.e., on the side facing inward into the packaging container manufactured from the packaging laminate. In other words, layer 23d is in direct contact with the packaged product. This innermost heat-sealing layer 23d forms a strong lateral heat seal of the liquid packaging container manufactured from the laminate packaging material and is a combination of one or more polyethylenes selected from LLDPE, so-called metallocene-LLDPE (m-LLDPE), produced by polymerizing ethylene monomer with C4-C8, more preferably C6-C8 α-olefin alkylene monomers in the presence of a metallocene catalyst.

[0254] The bulk layer 21d is laminated to the uncoated side (i.e., the side without the gas barrier coating) of a thin, barrier-coated fibrous paper substrate 25d, the same barrier-coated paper substrate as shown in Figure 1b, via an intermediate adhesive layer 26d of low-density polyethylene (LDPE). The barrier-coated paper substrate is dispersed and coated on the opposite side (inside) of the paper substrate 11d at approximately 2.0 g / m². 2 The paper substrate has a first oxygen barrier layer 13d which is PVOH, and an aluminum barrier layer 14d (i.e., an aluminum vapor-deposited layer) formed on the dry surface of the oxygen barrier layer 13d by physical vapor deposition with an OD of approximately 2. The paper substrate has a first vapor-resistant base coating 12d which is pre-applied by dispersion coating so as to be positioned beneath the first gas barrier layer or coating. This vapor-resistant base coating is a smoothing clay coating with a high concentration aqueous composition consisting of a clay coat, i.e., a latex binder and relatively high content of filler mineral particles (typically CaCO3 and / or kaolin clay). The intermediate adhesive layer 26d is LDPE and is melt-extruded between two paper webs in the form of a thin polymer melt curtain, thereby laminating the bulk layer and the barrier-coated paper substrate. This lamination step is performed as all three layers pass through the cooling press roller nip. The coating amount of the intermediate adhesive layer 26d is 10-20 g / m². 2 For example, 10-15 g / m 2 That is the case.

[0255] In this barrier-coated fibrous paper substrate, the inner surface (coated surface) is covered with an inner polymer multilayer portion 29d.

[0256] The inner polymer multilayer has three layers made of different polymers, namely, in this example, the innermost heat-sealable layer 23d made of a blend of 70% by weight mLLDPE and 30% by weight LDPE, and approximately 6 g / m² on the metal vapor-deposited surface of the barrier-coated paper. 2 The material has a bonding layer 24d made of, for example, ethylene acrylic acid copolymer (EAA) formed in a certain amount, which promotes adhesion to the barrier-coated paper substrate of the inner multilayer portion, and an intermediate load-supporting layer 28d containing HDPE or MDPE, a blend of HDPE or MDPE and LDPE, or LLDPE with a melt flow rate (MFR) of 4-20 g / 10 min (190°C / 2.16 kg) and a melting point of 115°C or higher. These three layers (24d, 28d, 23d) are formed simultaneously in a single melt co-extrusion coating step.

[0257] In a preferred embodiment, the three layers 24d, 28d, and 23d are formed in a two-step melt extrusion coating step. Specifically, in the first step, layers 24d and 28d are melt-extruded and solidified in a compression roller nip. In the second step, the innermost layer 23d is melt-extruded onto the solidified layers 24d and 28d.

[0258] In a preferred embodiment of this laminated structure, the intermediate load-bearing layer 28d is a blend of HDPE and LDPE in a weight ratio of 50:50. Such an internal polymer multilayer structure 29d significantly improves the strong load-bearing effect, high durability, and robustness when the laminated packaging material is folded and molded.

[0259] In a more preferred embodiment, the bulk layer 21d has a solid content of 2-7 g / m². 2 The aqueous adhesive composition of the starch-based adhesive is laminated to the uncoated side of the thin barrier-coated fibrous paper substrate 25d via an intermediate adhesive layer 26d-1.

[0260] In yet another embodiment, which can be combined with any of the embodiments described above, the outer liquid-tight and heat-sealable layers 22a;22b;22c;22d are aqueous dispersion coatings of acrylic-functional or acrylic acid-functional polyolefin polymers, with a dry solids content of 6-8 g / m². 2 It is formed by.

[0261] Figure 3a shows an embodiment of the main steps of the aqueous dispersion coating 30a. This can be used to apply a first gas barrier coating 13 consisting of an aqueous oxygen barrier composition onto a paper substrate, or to apply a vapor-resistant base coating 12 (although different apparatus and settings are required). Alternatively, it can be used to apply an aqueous adhesive composition for wet lamination of two webs, at least one of which has a fibrous cellulose surface.

[0262] The paper substrate web 31a (e.g., paper 11 in Figures 1a, 1b, and 1c) is transported to the dispersion coating station 32a, where an aqueous dispersion composition is applied to the substrate surface using rollers. In the case of a gas barrier composition, the aqueous dispersion composition may have a water content of 80-99% by weight. Therefore, a large amount of moisture is present on the wet-coated substrate surface, which must be removed by heat drying and evaporation to form a continuous coating with homogeneous and uniform quality in terms of barrier properties and surface properties (smoothness, wettability). Drying is performed by a hot air dryer 33a, which evaporates the moisture and removes it from the substrate surface. The substrate temperature passing through the dryer is kept constant at less than 100°C (e.g., less than 90°C, in the 70-90°C range) to avoid coating defects. Drying may be partially assisted by radiant heat from an infrared (IR) lamp in combination with hot air convection drying.

[0263] However, in the application of the steam-resistant base coating, the moisture content is significantly lower and the degree of drying is also different. The web of the paper substrate 34a coated with the steam-resistant base coating is smoothed by passing it through a soft calender nip, then sent for cooling, further wound onto a reel for intermediate storage, and subjected to the subsequent gas barrier coating step. Therefore, further coating steps include the production of a cellulose fiber substrate with a barrier coating by dispersion coating of a gas barrier composition, and / or vapor deposition coating of the aforementioned barrier vapor deposition coating 14.

[0264] Figure 3b shows the main steps of laminating two pre-formed material webs onto each other by the melt extrusion lamination method. For example, this applies when the bulk layers 21 (a, c, d) shown in Figures 2a, 2c, and 2d, respectively, are laminated onto the respective barrier-coated cellulose fiber substrates 25 (a, c, d).

[0265] In the first step, the bulk layer 21 is laminated onto the barrier-coated paper substrate 25 via an LDPE intermediate adhesive layer 26. The intermediate adhesive layer 26 is formed by melt-extruding a thin polymer molten curtain 26 from a die 32b located between the webs constituting the bulk layer 11 and the barrier-coated paper substrate 25, respectively. As a result, these three layers are laminated together, and the laminate 24 is cooled as it passes through the nip 32c between the press roller and the cooling roller, allowing the extruded LDPE intermediate adhesive layer 26 to solidify properly. The lamination temperature is approximately 300°C.

[0266] The resulting pre-laminate 35 is either wound onto a reel for intermediate storage or sent directly to the subsequent lamination step.

[0267] Figure 3c shows the final lamination step 30c in the manufacture of the packaging laminates 20a, 20b, 20c, or 20d shown in Figures 2a, 2b, 2c, and 2d, respectively. This is the step after each bulk layer 21a, 21b, 21c, or 21d is initially laminated onto the barrier-coated cellulosic fiber substrate 10a or 10b shown in Figure 1a or Figure 1b (i.e., 25a, 25b, 25c, or 25d in Figures 2a, 2b, 2c, and 2d, respectively).

[0268] As described in relation to Figures 2b, 2c, and 2d, bulk layer paperboards 21b;21c;21d may be laminated to barrier-coated paper substrates 10a;10b;25b;25c;25d by wet cold dispersion adhesive lamination or melt extrusion lamination. The wet dispersion adhesives 26b;26c;26d1 may be applied in the same or similar manner as described in relation to Figure 3a, but without drying or requiring only minimal heating.

[0269] As shown in Figure 2d, the step of laminating the bulk layer 21d onto the barrier-coated cellulose fiber substrate 25d may be carried out by either an extrusion lamination method of an intermediate thermoplastic adhesive layer (LDPE), as shown in Figure 3b, or a wet dispersion lamination method of an aqueous adhesive composition 26d-1, as shown in Figure 3a. However, the lamination step in the pressure roller lamination nip shown in Figure 3b is carried out so that it is absorbed onto the adjacent cellulose surface, i.e., the drying step 33a is omitted. However, melt extrusion 32b is excluded.

[0270] Figure 3c shows how the obtained pre-laminated paperboard webs 35;31b are fed out from the intermediate storage reel or directly from the paper pre-lamination station. The unlaminated sides, i.e., the printed sides, of the bulk layers 21a;21b;21c;21d are joined with the molten curtain 33d of LDPE at the cooling roller nip 33c to form the outermost layers 22a;22b;22c;22d of the laminate material. The LDPE is extruded from the extruder feed block and die 33b. The outer layers 22a;22b;22c;22d then pass through the second extruder feed block and die 34b and lamination nip 34c with the outer layers 22a;22b;22c;22d coated on the outside or printed side (i.e., outside). Here, the molten polymer curtain 34d is bonded and coated to the opposite side of the pre-laminate material, i.e., the inner barrier coating surface (paper substrate 10a;10b;25a;25b;25c;25d). As a result, the innermost heat-sealable layers 23a;23b;23c;24c, along with the further inner polymer layers (e.g., adhesive layers 24a;24b;24b';24c;24d), are co-extruded and coated to the inside of the paperboard pre-laminate web, forming the finished laminate packaging material 36. This is finally wound onto a storage reel (not shown).

[0271] A similar extrusion coating operation is performed to provide the laminated packaging material shown in Figure 2d.

[0272] In the preferred embodiment shown in Figure 2d, the three layers 24d, 28d, and 23d are applied in a two-step melt extrusion coating step. Specifically, in the first step, the adhesive layer 24d and the load-bearing layer 28d are coated by co-extrusion coating at the first extrusion coating lamination station, and in the second step, the innermost heat-sealable layer 23d is extrude-coated at the second extrusion coating lamination station. This means that after each extrusion coating step, the melt-extruded coated polymer film solidifies in the lamination roller nip by contact with the substrate web on the one hand and with the cooling roller on the other. As a result, at least the inner surface of the intermediate load-bearing layer 28d solidifies at its surface and interface before the innermost layer 23d is applied.

[0273] The two co-extrusion steps in the laminated roller nips 33c and 34c may instead be carried out as two consecutive steps in reverse order.

[0274] In another embodiment, one or both of the outer layers may instead be coated in a pre-lamination station. In this station, the extruded coating layer is first coated on the outside of the (printed) bulk cardboard layer or on the metal vapor-deposited surface of the barrier-coated paper substrate, and then the two pre-laminated paper webs may be joined to each other as described above.

[0275] In yet another embodiment, the inner layer of the heat-sealable and liquid-tight thermoplastic layer is applied in the form of a pre-fabricated film and laminated onto the coated surface of the barrier-coated paper substrates 10a;10b;10c.

[0276] Figure 4a is a schematic diagram showing an example of a plant 40a that performs, for example, an aluminum metal coating on a web substrate of the present invention by physical vapor deposition (PVD). The paper substrate 41, which has been coated with a base coating and a first gas bar coating (i.e., dispersion coating), undergoes continuous vapor deposition 40 of evaporated aluminum on its coated surface to form an aluminum metal vapor deposition layer. Alternatively, it is subjected to a mixture of oxygen and aluminum vapor to form a deposited aluminum oxide coating. This coating is provided with a thickness of 5 to 100 nm, preferably 10 to 50 nm, to form the barrier coated paper 43 of the present invention (or the barrier coated polymer film substrate 28a used in the laminated packaging material of Figure 2c). The aluminum vapor is generated by ion bombardment of a solid aluminum block 42, which is the evaporation source. For the aluminum oxide coating, oxygen gas may be injected into the plasma chamber via an intake port.

[0277] Figure 4b is a schematic diagram showing an example of a plant 40b for depositing a coating of, for example, hydrogenated amorphous diamond-like carbon on a web substrate of the present invention by plasma chemical vapor deposition (PECVD). On one side of the web substrate 44a, continuous PECVD is applied by plasma in a plasma reaction zone 45 formed in the space between a magnetron electrode 46 and a cooled web transport drum 47, which also functions as an electrode. During this time, the substrate is transported along the circumferential surface of the drum within the plasma reaction zone by a rotating drum, and then wound onto a roller as a barrier-coated web substrate 44b. The plasma for depositing the amorphous DLC coating can be generated, for example, by injecting a gas precursor composition containing organic hydrocarbon gases such as acetylene or methane into the plasma reaction chamber. Other gas barrier coatings, such as silicon oxide films (SiOx) using organosilicon compound precursor gases as starting materials, can also be applied by a PECVD method based on a similar principle. The PECVD plasma chamber is maintained in a vacuum state by continuously exhausting the inside of the chamber from outlets 48a and 48b.

[0278] Figure 5a shows an example of a packaging container 50a manufactured from the packaging laminate of the present invention. This packaging container is particularly suitable for beverages, sauces, soups, etc. Typically, the capacity of such a packaging container is about 100 to 1000 ml. It can be any shape, but is preferably brick-shaped, each having a longitudinal sealing portion 51a and a transverse sealing portion 52a, and optionally equipped with an opening device 53. In another embodiment (not shown), the packaging container can be wedge-shaped. To obtain such a “wedge shape”, only the bottom of the packaging container is folded and molded, and the transverse heat-sealed portion of the bottom is hidden under a triangular corner flap. This corner flap is folded and fused tightly to the bottom of the packaging container. The upper transverse sealing portion is not folded. This makes the partially folded packaging container easy to handle and maintains sufficient dimensional stability for placement on grocery store shelves or flat surfaces.

[0279] Figure 5b shows an example of an alternative packaging container 50b manufactured from the alternative packaging laminate of the present invention. The alternative packaging laminate is thinner due to having a thinner paper bulk layer and therefore does not have sufficient dimensional stability to form a parallelepiped or wedge-shaped packaging container and is not folded after lateral sealing 52b. The packaging container remains a pillow-shaped pouch container and is distributed and sold in this form.

[0280] Figure 5c shows a gable-top package 50c formed by folding a pre-cut sheet or blank from a laminated packaging material consisting of a bulk layer of cardboard and a barrier-coated paper substrate of the present invention. A flat-top package may also be formed from a similar material blank.

[0281] Figure 5d shows a bottle-shaped packaging container 50d. It combines a sleeve 54 formed from a pre-cut blank of laminated packaging material with a top 55 formed by injection molding plastic together with an opening device such as a screw cork. This type of packaging is sold under the trademark names Tetra Top® and Tetra Evero®, for example. These particular containers are manufactured by attaching a top 55 molded with the opening device closed, connecting it to a tubular sleeve 54 made of laminated packaging material, sterilizing the thus formed bottle-shaped container, filling it with food, and finally folding and sealing the bottom of the container.

[0282] Figure 6 shows the principle described in the introduction of this application. Specifically, the web of the packaging material is overlapped by overlapping the longitudinal edges 62, 62' of the web and heat-welding them to each other to form a tube 61, thereby forming an overlapping joint 63. This tube is continuously filled with the liquid food to be filled (64) and divided into individual filled packages by double transverse seals 65 that are repeatedly applied to the tube at predetermined intervals below the level of the contents inside the tube. The packages 66 are separated by cutting between the double transverse seals (upper seal and lower seal) and finally formed into a predetermined geometric shape by folding along pre-formed fold lines in the material.

[0283] Figure 7 shows images of cross-sections of a series of laminated packaging materials, consisting of comparative material G and the laminated packaging material of the present invention, taken by X-ray tomography. The number of vapor blisters in the inner polymer layer of the laminated packaging material increases dramatically in proportion to the density of the paper substrate layer. The outside of each laminate is a white clay coat layer, and adjacent laminated layers (layers adjacent to the white clay coat layer) exhibit a uniform gray color, which collectively represents the inner polyethylene-based layers. As shown in the figure, the density of fibrous cellulose is approximately 980 kg / m³. 3 In comparative material G, a laminated sample using high-density paper, multiple large blisters can be observed.

[0284] Figure 8a shows how the number of blisters formed by moisture-containing air in a fibrous paper substrate increases exponentially with increasing density of the fibrous portion of the paper substrate. This is at 700-1000 kg / m³. 3 These are the results obtained when tested under identical conditions across the entire range.

[0285] Figure 8b shows that the number of blisters formed by moisture-containing air within the fibrous paper substrate is in the lower end of the density range, i.e., 700-850 kg / m³. 3 This figure shows how the density of the fibrous portion of the paper substrate relates to this range. This relationship can increase more linearly.

[0286] Therefore, by employing the barrier-coated cellulosic fiber substrate of this disclosure in a laminated packaging material, the following advantages can be achieved:

[0287] The fibrous, and therefore porous, portions of the cellulose fiber substrate allow for the proper discharge of the rapid bursting of steam and moist air generated from heated areas within the plane of the fiber substrate.

[0288] A vapor-resistant base coating is a base coating filled with inorganic particles or fillers, ensuring that sudden bursts of vapor or moist air are trapped in the fibrous portion of the substrate layer and do not escape through the vapor-resistant base coating. In this way, the vapor-resistant base coating ensures that so-called "blistering" does not damage the additional polymer layer inside the vapor-resistant base coating. Such additional gas barrier layers and polymer inner layers / coatings must remain intact to ensure the integrity and food safety of the packaging container molded and heat-sealed from the laminated packaging material.

[0289] The use of porous cellulose-based substrates, due to their fibrous nature, combined with such vapor-resistant base coatings, provides a good base and substrate for even thinner, more sensitive gas barrier coatings that maintain their gas barrier properties after bending and molding, as measured by corresponding fold-fastness OTR measurements. This was an unexpected result, as it had previously been concluded that improving the performance of bend-molded packaging containers required increasing the density of the fibrous portion of the substrate. Therefore, expensive high-density paper substrates, which inherently provide a high level of oxygen barrier properties during lamination, may not necessarily be required for this purpose.

[0290] The initial oxygen barrier properties provided by such gas barrier coatings, i.e., the oxygen barrier properties measured by the OTR test method on a flat sample of laminated packaging material containing a cellulose fiber substrate with a barrier coating, are effective because the flexible, vapor-resistant base coating containing inorganic particles is smoothed and densely packed, giving the substrate surface low porosity and low surface roughness. This allows for thin application and efficient gas barrier coating, even though it is inherently sensitive to mechanical damage.

[0291] Further experiments on preferred embodiments of heat-sealable laminated packaging materials:

[0292] Experiment 3a Figure 9a shows the OTR of three equivalent packaging laminates, differing only in the paper barriers A, B, and C. Each laminate also differed in its internal polymer layer configuration, as shown in the figure. Barrier-coated papers B and C have superior overall oxygen barrier material compared to barrier-coated paper A, and therefore provide better overall performance, i.e., a lower package OTR level.

[0293] The main layer composition of the laminated packaging material was as follows: / / LDPE (12g / m 2 ) / Cardboard 80 mN CLC duplex BKG / LDPE (15g / m2 ) / Paper base material / 2x1.0g / m 2 PVOH (total 2.0 g / m²) 2 ) / Metal deposition (OD approx. 2.0) / Inner surface / / (For paper C laminate, the dry coating amount of PVOH is 2.8 g / m²) 2 (was) Here "Inner self" refers to one of the following: "Film": / EAA (6g / m 2 ) / LDPE (13g / m 2 ) / Cast LLDPE film / / "HDPE": / EAA (6g / m 2 ) / / HDPE (15g / m 2 ) / mL LDPE 70% by weight + LDPE 30% by weight blend (14g / m²) 2 ) / / "mPE": / EAA (6gm 2 ) / mL LDPE 70wt% + LDPE 30wt% blend (29g / m²) 2 ) / /

[0294] Ineos LDPE grade 19N730 was used throughout the entire layer. The "mPE" layer is manufactured from Dow's blend grade "Elite 5800" and corresponds to a blend of approximately 70% by weight mLLDPE and approximately 30% by weight LDPE. The EAA grade used was Dow's Primacor 3540. The LLDPE film is a cast biaxially oriented LLDPE film with a thickness of 18 μm and a basis weight of 17 g / m². 2 That was the case. The HDPE grade was Dow's Dowlex 2006G.

[0295] The barrier-coated paper substrates A and B shown in Figure 9a were each subjected to the following barrier coatings.

[0296] A two-step continuous coating using a water-soluble PVOH dispersion (Poval® 6-98, manufactured by Kuraray, with a solid content of approximately 10% by weight) was applied to the upper surface of a base-coated paper substrate using a roller coating method. After each step, evaporation drying was performed while maintaining the substrate surface temperature below 90°C, and each coating layer was coated at approximately 1.0 g / m² on a dry weight basis. 2 PVOH was added. This resulted in a total dry weight of approximately 2.0 g / m². 2 PVOH was applied. Then, a thin film metal deposition with an OD of approximately 2.0 was performed on the paper substrate coated with PVOH using the PVD method.

[0297] Barrier coating paper substrate C uses the same PVOH (Poval® 6-98 manufactured by Kuraray Co., Ltd., solid content approximately 10% by weight) as a substitute, with intermediate drying and final drying steps performed while maintaining the substrate surface temperature below 90°C, at a rate of 0.7 g / m². 2 The coating was applied four times consecutively. The PVOH-coated paper substrate was then subjected to thin-film metal deposition by PVD, resulting in an OD of approximately 3.5.

[0298] The material lamination was carried out on a pilot-scale lamination line. The lamination speed was approximately 100 m / min.

[0299] Duplex CLC cardboard was a conventional clay-coated cardboard. The barrier coating surface of the paper substrate was positioned on the inside of the laminated structure, corresponding to the inside of the packaging container manufactured from the laminated material.

[0300] The laminated packaging material was manufactured by melt extrusion lamination at 310°C. During this process, an intermediate adhesive layer made of conventional low-density polyethylene (LDPE) was applied at approximately 15 g / m². 2 This was used to laminate the cardboard to the back of each barrier-coated paper. The outer layer of the cardboard was approximately 12 g / m². 2 The LDPE was melt-extruded and coated. As a result, the gas barrier coated paper substrate was melt-extruded or laminated to have a different internal polymer multilayer structure on the opposite barrier-coated inner side.

[0301] The packaging containers were manufactured from the respective laminated materials using a Tetra Brik® A3 / CF type filling machine, and the packaging size was 200ml "Slim" (200S).

[0302] After emptying the filled containers and purging them with nitrogen, the oxygen permeability to each container was measured under 0.2 atmospheres in accordance with ASTM F1307-14.

[0303] The results are shown in the graph in Figure 9a.

[0304] The oxygen permeability (OTR) of packaging containers manufactured from equivalent laminates, with the same barrier coating paper, is maintained at a similarly low and good level whether a pre-fabricated cast LLDPE film is used as the heat-sealing innermost layer, or whether a co-extruded coating inner layer consisting of a metallocene catalyst-catalyzed mLLDPE and LDPE blend is used. Even when the inner polymer layer configuration includes an internal load-bearing layer made of HDPE or MDPE instead of a pre-fabricated film, and the innermost layer is combined with the same mLLDPE and LDPE blend layer, the OTR of the packaging container remains very good and may even be further improved.

[0305] In particular, for low-performance paper substrates that have low flexibility and are prone to cracking of the thin barrier coating due to cellulose material rupture when the paper is folded, it has been found that an inner polymer multilayer with load-bearing capacity and resistance is necessary. As a first solution for producing fold-resistant packaging materials, certain expensive pre-fabricated cast LLDPE films have been used. However, the structure of the laminated packaging material according to the first embodiment has been demonstrated to be a cost-effective solution that maintains excellent gas permeability characteristics even after the material is formed into foldable packaging. Furthermore, the inner polymer multilayer can remain intact on its own without causing thinning of the polymer layer or other defects.

[0306] In connection with the above development, it has been found that certain types of extruded linear low-density polyethylene (EC-LLDPE) with a melting point Tm of 124°C exhibit even better performance in several aspects due to different mechanisms and slightly different secondary properties. However, such improvements have not been observed when conventional LLDPE grades with a low melting point Tm of 110°C or less, which are used as conventional inner layer (innermost layer) heat-sealing layers, were tested for (co)extruded coating.

[0307] Experiment 3b In this experiment, similar laminated packaging materials were manufactured using the same method and materials with barrier-coated paper substrate A, and similar pre-filled packaging containers were created in the same manner. The main layer composition of the laminated packaging material is as follows: / / LDPE (12g / m 2 ) / Cardboard 80mN CLC duplex BKG / LDPE (15 g / m) / Paper base A / 2x1.0g / m 2 PVOH (total 2.0g / m²) 2 ) / Metal deposition (OD approx. 2.0) / Inner surface / / Here "Inner self" is one of the following: "HDPE": / EAA (6g / m 2 ) / A blend of 50 wt% HDPE and 50 wt% LDPE (15 g / m²) 2 ) / mL LDPE 70wt% + LDPE 30wt% blend (14g / m²) 2 ) / / "mPE": / EAA (6g / m 2 ) / mL LDPE 70wt% + LDPE 30wt% blend (29g / m²) 2 ) / / "EC-LLDPE": / EAA (6g / m²) 2 ) / Dow Elite 5811 100wt% (15g / m²) 2 ) / mL LDPE 70wt% + LDPE 30wt% blend (14g / m²) 2 ) / /

[0308] Inoes LDPE grade 19N730 was used for all layers. The innermost heat-sealing layer, "mPE," is manufactured from Dow's blend grade "Elite 5800," which is equivalent to a blend of approximately 70% by weight mLLDPE and approximately 30% by weight LDPE. The EAA grade used was Dow's Primacor 3540. The HDPE grade was Ineos' Rigidex 6070FA.

[0309] After emptying the filled packages and purging them with nitrogen, the oxygen permeability to each package was measured in the same manner under 0.2 atmospheres, in accordance with ASTM F1307-14. The results are shown in the graph in Figure 9b.

[0310] The results in Figure 9b show that a laminated material having an intermediate load layer blended with HDPE and LDPE in a weight ratio of 50:50 in the inner polymer multilayer provides a superior (i.e., lower) oxygen permeability (OTR) in a folded empty packaging container compared to a corresponding conventional laminated material having an inner polymer multilayer. On the other hand, the laminated sample of the present invention, which employs EC-LLDPE (i.e., 100 wt% Dow Elite 5811) as the load-bearing and dispersing layer as the intermediate layer, also showed significantly better OTR than a laminated material with a conventional inner polymer multilayer structure. However, the OTR was slightly inferior compared to a laminated material having an HDPE blend layer as the load-bearing layer. Therefore, this special EC-LLDPE load-bearing and dispersing layer enables the realization of a superior packaging container that maintains the oxygen barrier properties of the barrier-coated paper substrate well.

[0311] Experiment 4a To further test the ability of the laminate to withstand folding formation in the filling machine, the laminate from Experiment 3 was subjected to multiple uniaxial folding, unfolding, and refolding tests using a folding test apparatus. The OTR was then measured for the planar material with one unfolded crease. The robustness of the material against "folding fatigue" was tested by repeating the folding process several times. This is a crucial aspect of the folding robustness of non-foil (i.e., aluminum foil-free) laminated liquid carton materials consisting of barrier-coated paper substrates, and this method measures the extent to which the inner polymer layer protects the paper barrier material.

[0312] The ability of the inner polymer multilayer to prevent cracks from forming in the paper substrate when folded, or at least to reduce the size of any cracks that do occur, may be observed on the metal barrier coating using an optical microscope or magnifying glass.

[0313] To study the appearance of "thinning defects" in the inner polymer multilayer structure, X-ray tomography, microtome sectioning, and optical microscopy may be necessary.

[0314] An inner polymer multilayer with a higher and more appropriate tensile modulus is considered to have superior tensile resistance, as its thickness does not change when stretched along a fold. Such a polymer layer contributes to improved oxygen barrier properties by preventing the expansion of cracks that occur in folded paper and also preventing crack formation in the barrier coating. Overall, this structure is expected to be more robust against bending forces and have higher load-bearing capacity.

[0315] Figure 10a shows the results of the so-called "OTR bending strength" test. This relates to a laminate having paper A as a barrier-coated paper substrate, an LLDPE cast film on the inner surface, and an improved paper barrier C (each configuration of the inner polymer layer examined in Experiment 3a) that conforms to claims 1 to 12 of the present invention. The laminate material was repeatedly folded and unfolded, and the OTR was measured after 2 and 4 folding repetitions.

[0316] Surprisingly, the fold strength of laminated paper C material tended to be even better when an HDPE layer was co-extruded and coated adjacent to the innermost LLDPE blend layer compared to when a pre-fabricated LLDPE film was used as the innermost layer.

[0317] Based on the results using paper barrier A, it can be concluded that using a pre-manufactured LLDPE film as the innermost layer shows significant improvement compared to using only an inner polymer multilayer consisting of a single layer of a blend of 70% LLDPE and 30% LDPE.

[0318] These results demonstrate that both the inner film layer and the HDPE co-extruded layer significantly improve such bending fatigue and reduce oxygen permeability (OTR) loss in folded and molded packaging containers.

[0319] As a whole, the extruded coated inner polymer multilayer structure, consisting solely of an extruded HDPE coating layer, is an excellent material for forming part of the inner polymer layer of a paper barrier laminate. In particular, when combined with the barrier-coated fibrous cellulose substrate of the present invention, it provides improved OTR fold fastness compared to an inner polymer containing a pre-fabricated LLDPE film. At the same time, compared to using a pre-fabricated LLDPE film for the inner polymer layer, using only an extruded coated polymer layer in the inner polymer multilayer portion improves the overall openability of the packaging material.

[0320] The composition of the inner polymer multilayer portion tested in Figure 10a all had a total polymer basis weight of approximately 35 g / m². 2 The innermost layer is a blend of 70% mL LDPE and 30% LDPE, with a density of 15 g / m². 2 EAA polymer is used as an adhesion-promoting layer on the barrier coating side at a rate of 6 g / m². 2 That was the case.

[0321] A three-layer co-extruded coated inner polymer multilayer structure with an HDPE intermediate layer has been demonstrated to be a viable alternative to pre-fabricated cast and stretched LLDPE films in terms of the integrity of the inner polymer and paper barrier in foldable molded packages.

[0322] Experiment 4b To understand the effect of including a selected EC-LLDPE layer (as defined in claim 1) instead of the HDPE layer in the inner polymer multilayer, comparative measurements were also performed with a similar structure where the only difference was that the inner polymer multilayer was an extruded coating grade LLDPE with a high melting point of 115°C or higher, for example, 120°C or higher, specifically with a Tm of 124°C in this experiment.

[0323] Therefore, the comparative laminate and the laminate of the present invention had a three-layer internal polymer multilayer structure, similar to Experiment 2a. That is, / EAA 6g / m 2 / “X” 15g / m 2 Blend of 70wt%mL LDPE and 30wt% LDPE, 14g / m² 2 / / Here, "X" is: "EC-LLDPE" (LLDPE for extrusion coating), a high-melting-point LLDPE that can be extruded and has load-bearing and load-distributing properties, is used in Dow's Elite 5811. "EC-LLDPE 50%" (50% by weight of LDPE blended with the same EC-LLDPE), "HDPE 20%" (a blend of HDPE and 80% by weight LDPE), "LDPE", "LDPE+" (meaning the weight ratio of the three layers, including the LDPE layer, is 6 / 20 / 18) "mPE" (meaning a blend of 70 wt% mL LDPE and 30 wt% LDPE).

[0324] The LDPE used was Ineos 19N730, the EAA was Dow's Primacor 3540, the HDPE was Dow's Dowlex 2006G, and the EC-LLDPE was Dow's Elite 5811.

[0325] Figure 10b shows that the conventional inner layer using only EAA and "mPE" heat-sealed blend performs poorly with respect to uniaxial and repetitive folding along the fold line of the cardboard. This is part of the underlying problem of the present invention. On the other hand, replacing the intermediate mPE layer with conventional extruded grade LDPE improves the bending resistance of the entire inner layer. Polymer basis weight: 6+20+18 g / m² 2 When the amount was increased to (a sample called "LDPE+"), the uniaxial bending resistance or properties improved only slightly, which is why it can be concluded that simply increasing the amount of polymer in the coating layer is not very efficient. The improvement was similar when the intermediate layer was replaced with a relatively low amount of 20 wt% HDPE. When the intermediate layer was replaced with selected "EC-LLDPE", the results worsened again, so the use of such linear low-density polyethylene is generally not recommended compared to using an intermediate inner layer of HDPE or LDPE polymer.

[0326] However, it was further confirmed that blending EC-LLDPE with 50% by weight of LDPE slightly improved its load-bearing capacity against uniaxial bending.

[0327] Experiment 5 Figures 11a to 11c illustrate how the openability of packaging containers manufactured using the laminated packaging material is ensured by the laminated packaging material of the present invention.

[0328] In the illustrated examples in Figures 11a to 11c, laminated paper barrier A, as described in Figure 9a, was manufactured and laminated with inner polymer multilayer sections of different configurations. For the three types of laminates, using paper straws with identical dimensions and rigidity characteristics, the maximum opening force, maximum energy, and total energy required to penetrate the pre-cut and laminated holes for the straws were tested, and the three samples were compared with each other.

[0329] Therefore, the following applies to Figures 11a to 11c: Extrusion of comparative structure = Conventional co-extruded coating with two inner layers (used in aluminum foil-based carton materials) (adhesive polymer + innermost heat-sealable layer), i.e. / EAA (6g / m²) 2 ) / mL LDPE 70wt% + LDPE 30wt% blend (29g / m²) 2 ) / / Comparative structure film = Film inner layer = / EAA (6g / m²) 2 ) / LDPE (13g / m 2 ) / Pre-manufactured LLDPE film 17g / m 2 / / Laminate of the present invention = Co-extruded coated 3-layer structure with an inner load-bearing layer, i.e., / EAA(6g / m 2 ) / / HDPE (15g / m 2 ) / mL LDPE 70wt% + LDPE 30wt% blend (14g / m²) 2 ) / / The polymer used is the same as described above in relation to Figure 9a.

[0330] Figure 11a shows the maximum relative force required for a paper straw to penetrate the laminated polymer film through a pre-cut opening in the cardboard of the laminated packaging material. Since the pre-cut opening is laminated to the outer and inner polymer layers, the outer and inner polymer layers are laminated to each other within the opening region, resulting in the formation of a film composed solely of polymer layers (including a thin-film barrier layer if necessary, unless pre-cut together with the bulk layer). The unit of measurement is Newtons (N). As expected, the force required for the comparative material with the aforementioned pre-fabricated cast LLDPE film was maximum when penetrating in the mechanical direction (MD) of the material. All values ​​in Figure 11a are shown as relative values ​​to this value. Therefore, the laminate of the present invention reduces the required force to a normal level, keeping it only slightly higher than the conventional two-layer internal laminate as described above.

[0331] Figure 11b shows the relative maximum energy required for a paper straw to penetrate the same three types of laminated materials. The energy required for the inventive laminated material is lowest in the mechanical direction (MD) and at the same level as conventional laminated materials in the transverse direction (CD). The unit of measurement was Nm.

[0332] Figure 11c shows the total relative energy required for a paper straw to penetrate the same three types of laminated materials. As mentioned above, the total energy required for the laminated material of the invention is only slightly higher than that of a typical two-layer internal laminated material, and is within a normal and acceptable level. The unit of measurement is Nm.

[0333] In both Figures 11b and 11c, the measurement results are shown as relative values ​​to the MD measurements in the film-covered comparison structure.

[0334] In conclusion, in the case of a straw opening, i.e., a through-opening mechanism for a pre-cut hole in the membrane, the laminate of the present invention having a load-bearing extruded coating layer exhibits significantly improved openability compared to using a pre-fabricated LLDPE film for load-bearing. This is also true when the extruded coated load-bearing layer exhibits significantly improved flexural rigidity compared to a co-extruded coated inner polymer multilayer without such a load-bearing layer.

[0335] In conclusion, corresponding laminates containing pre-fabricated films in the inner layer configuration may still exhibit superior performance in other aspects of the integrity of the inner polymer multilayer. However, such pre-fabricated films have significant drawbacks, such as making it difficult to supply the laminating material and open the packaging container, making them an undesirable alternative overall compared to conventional mLLDPE blend internal configurations. Furthermore, suitable pre-fabricated films are not only significantly more expensive themselves, but also incur additional costs in the lamination step, further exacerbating these drawbacks.

[0336] It was found that simply adding an extruded, HDPE-coated load-bearing layer to the inner polymer multilayer structure provides a cost-effective alternative to laminating pre-fabricated films, and is also superior in terms of ease of opening.

[0337] Similarly, including an extruded coating layer of a selected load-bearing and load-distributing EC-LLDPE with a melting point of 124°C in the inner polymer multilayer structure is expected to provide good openability. However, due to its high load-distributing properties, the open resistance may be slightly higher, but in any case, the open resistance will be significantly lower than comparative samples containing a pre-fabricated biaxially oriented LLDPE polymer film in the inner layer. In conclusion, a configuration in which the intermediate layer is EC-LLDPE instead of HDPE in an inner polymer multilayer structure (i.e., a 3-layer structure) reliably exhibits superior performance compared to materials containing a pre-fabricated film in the inner polymer multilayer.

[0338] Experiment 6 Furthermore, comparative tests were conducted on OTR bending fastness. In these tests, the HDPE layer was replaced with an HDPE blend layer containing either 20% by weight or 50% by weight of conventional extruded coating grade LDPE. The total basis weight of the inner polymer multilayer in this example was approximately 35 g / m². 2 The main layered structure was as follows: / / LDPE (12g / m 2 ) / Cardboard 80 mN CLC duplex BKG / LDPE (15g / m 2 ) / Thin paper substrate A / 2xPVOH (total g / m²) 2 ) / Metal deposition (OD approx. 2.0) / / EAA(6g / m 2 ) / / HDPE (or HDPE blend) (15g / m 2 ) / mL LDPE 70wt% + LDPE 30wt% blend (14 g / m²) 2 ) / /

[0339] Two types of HDPE polymers were tested: Dow's Dowlex 2006G and Ineos' RigidexFA. Ineos' 19N730 was used as the LDPE blend polymer.

[0340] As shown in Figure 12, additional experiments in which up to 50% by weight of LDPE was blended into the HDPE polymer of the load-bearing "HDPE" intermediate layer yielded comparable good OTR results at a lower value in the OTR bending rigidity test.

[0341] As a result, even when the amount of HDPE polymer in the load-bearing layer was reduced, the oxygen permeability after repeated uniaxial bending remained at a relatively low level. In other words, the blends within the indicated range exhibit the behavior of the inner polymer multilayer of a three-layer structure containing HDPE, rather than the behavior of the inner surface structure of a conventional corresponding mLLDPE blend. This can be further confirmed in Figure 13 (Experiment 7).

[0342] Experiment 7 In another series of tests, the results of which are shown in the table in Figure 13, bending tests were performed in the same manner as in the previous experiment on similar laminates but with a thinner inner layer polymer structure. However, the total weight of the laminate was only about 26 g / m². 2 In this test, the inner layer was processed using a two-stage continuous extrusion coating. For comparison, an inner layer having only an m-LLDPE blend layer was also tested using a two-stage continuous extrusion coating.

[0343] The main layer composition of the laminated packaging material was as follows: / / LDPE (12g / m 2 ) / Cardboard 80 mN CLC Duplex BKG / LDPE (15g / m 2 ) / Paper base material A / 2xPVOH (total 2g / m 2 ) / Metal deposition (OD approx. 2.0) / Inner surface / / Here "Inner self" is one of the following: "HDPE": / EAA (6g / m 2 ) / / HDPE (10g / m 2 ) / mLLDPE 70wt% + LDPE 30wt%(10g / m 2 ) blend / / "mPE": / EAA (6g / m 2 ) / mL LDPE 70wt% + LDPE 30wt% blend (20g / m²) 2 ) / /

[0344] The polymer grade used was the same as in the previous experiment 6, and as shown in the figure, the HDPE grade used in this experiment was RigidexFA from Ineos.

[0345] The results in Figure 13 show that the two-stage extrusion coating of the inner layer of the mLLDPE blend yielded results equivalent to those of a single co-extrusion coating, i.e., obtaining the same layer thickness in a single extrusion coating. Therefore, the two-stage extrusion coating did not contribute to improving the OTR flexural rigidity of this inner layer configuration.

[0346] On the other hand, for laminates containing HDPE as a load-bearing intermediate layer, when the innermost mLLDPE blend layer was extruded separately from the innermost layer, that is, when the extrusion coating of the inner polymer layer was carried out as two consecutive coating steps and the coating layer was solidified in each step, it showed superior OTR bending rigidity compared to the inner layer of mLLDPE blend composed of both a single and a two-step extrusion coating configuration using mLLDPE blend on the inner surface.

[0347] Therefore, it was confirmed that the use of an HDPE load-bearing layer significantly improved the OTR fold rigidity in two and four folds, respectively, compared to a comparative inner surface sample having only the conventional mLLDPE blend innermost layer.

[0348] Furthermore, it was confirmed that when HDPE was blended with 50% by weight of LDPE and subjected to a two-stage extrusion coating, the OTR bending strength was further improved even when processed into a thin layer.

[0349] In most cases, packaging laminates with a three-layer inner layer using 100% HDPE in the middle layer are considered to provide packaging containers that combine excellent package OTR and improved OTR fold strength.

[0350] However, packaging laminates can sometimes produce defective packages (formed by the filling machine), resulting in low integrity and robustness (including fold robustness). In such individual cases, the OTR (Output Traffic Rate) of the defective packages can also be excessively high. This is thought to be due to the anisotropic properties of extruded coated HDPE. Therefore, it has been confirmed that using HDPE mixed with LDPE in the load-bearing layer reduces anisotropic behavior, thereby improving overall fold robustness and reducing the occurrence of defective packaging.

[0351] Experiment 8a In addition to uniaxial bending fatigue along the fold lines of the cardboard, the biaxial bending region of the packaging material used to form box-shaped containers is a particularly defect-sensitive area that sometimes produces defective containers with high package OTR and incomplete inner polymer layers.

[0352] Therefore, a further important aspect of package integrity concerns how well the inner polymer layer withstands damage during biaxial double folding in the folding process of paperboard laminates. To specifically test this integrity characteristic, a 35 g / m² sample was tested in relation to Figure 12. 2 A sample of the same laminated material having an inner polymer layer was first folded 180 degrees in a bending test apparatus, and then folded a second time 180 degrees perpendicular to the first fold. This gave the double fold a specific geometric shape. This created a second fold perpendicular to the first fold, acting severe strain and stress on the inner polymer layer. After unfolding again, a minimum level of high voltage was applied to the planar material to test whether dielectric breakdown occurred due to thinning or defects in the inner polymer layer of the barrier coating paper. If breakdown was not observed, the test was continued by gradually increasing the voltage until dielectric breakdown finally occurred. The voltage value at the time of breakdown was recorded. This is a test to evaluate the risk of thinning of the material layer under stress conditions, i.e., a stress test of the material.

[0353] The results are shown in Figure 14a, demonstrating that in an inner polymer multilayer configuration with a layer of HDPE blended with 20-50% by weight of LDPE as a load-bearing layer, dielectric breakdown does not occur until an applied voltage several kV higher is reached compared to a pure HDPE layer of the same thickness. This effect is confirmed regardless of the grade of HDPE used.

[0354] Therefore, to optimize overall bending strength from the perspective of both uniaxial and biaxial bending along the fold line, it is preferable to blend HDPE with LDPE at a ratio of 20-80% by weight, for example, 20-70% by weight, for example, 20-60% by weight, and even further, for example, 20-50% by weight.

[0355] Experiment 8b We compared the laminate from Experiment 6a with a similar three-layer inner surface packaging laminate, but with the intermediate layer being 100% EC-LLDPE (Dow Elite 5811) as the laminate material in Experiment b. The results are shown in Figure 14b.

[0356] As shown in Figure 14b, the laminated structure with unmixed EC-LLDPE as the inner intermediate layer showed superior performance in biaxial bending compared to all HDPE laminated structure samples. This is an important property because biaxial bending can damage both the thin barrier coating layer and the inner polymer multilayer. Laminates with improved inner layer performance due to the load-bearing and dispersing properties of EC-LLDPE during biaxial bending may compensate for the inferior oxygen permeability fastness during uniaxial bending. Blending a portion of LDPE with EC-LLDPE slightly improves the load-bearing and dispersing effect during uniaxial bending, but blending is undesirable for biaxial bending performance. This is also evident from the comparative test results shown in Figure 14c, namely, as the proportion of LDPE in the EC-LDPE-containing layer increases, the load-bearing and load-dispersing effect of the inner polymer multilayer clearly decreases.

[0357] Experiment 9a A more important aspect of package integrity is the quality of the inner polymer multilayer layers themselves, ensuring they are free from defects such as pinholes and thin sections that may occur during extrusion coating or lamination steps. This characteristic is also evaluated by a voltage withstand test applied with gradually increasing voltage. The test is conducted using a so-called "Fischer HV5" type "poroscope," measuring the basis weight of the inner polymer multilayer structure at approximately 26 g / m². 2 This test is performed on laminated samples. This test demonstrates the integrity of the inner layer in areas of the molded packaging container where the laminated material forms flat, unfolded, and unfolded panels, i.e., in areas corresponding to the unfolded packaging walls of the packaging container.

[0358] Figure 15a is similar to Figures 14a and 12, meaning the basis weight of the inner polymer multilayer is approximately 35 g / m². 2 This figure shows the results for the laminated material samples. A similar trend was observed, meaning that blending with HDPE improved the quality and overall resilience of the inner polymer multilayer. The 100% HDPE layer showed better resistance to low applied voltages, but in any case, there was a risk of dielectric breakdown when higher voltages were applied and in more packaging containers. Blending 20 wt% LDPE with HDPE reduced the total number of weak points, and blending with approximately 50 wt% LDPE further reduced the number of weak points.

[0359] Experiment 9b As shown in Figure 15b, similar laminated materials with an internal polymer multilayer structure using EC-LLDPE in the internal intermediate layer showed surprisingly good performance in the same poroscopy test. This result offsets the low performance of uniaxial bending rigidity and shows improved load support / dispersion effect and layer quality in the internal polymer multilayer structure, resulting in an overall further improved laminated material. This improves the overall integrity of the package related to the internal polymer multilayer section.

[0360] Experiment 10a Furthermore, for similar reasons, laminated materials with an internal polymer multilayer formed by a two-stage extrusion coating were tested using a poroscope in a planar unfolded state. Figure 16a shows that when Ineos 50% HDPE RigidexFA is used for the internal intermediate layer, the two-stage extrusion coating is superior to that of a material where all three layers are co-extruded in one step. In addition, the two-stage extrusion coating layer is superior to the single-step co-extrusion coating sample (36 g / m²). 2 Compared to that, it is thinner (approximately 26g / m²). 2Therefore, it should normally be more sensitive to applied voltage, but on the contrary, surprisingly, it proved to be of higher quality and more robust. In the two-stage extrusion coating, the adhesive polymer EAA and the load-bearing HDPE-containing layer were co-extruded onto the barrier coating paper and solidified, and then the innermost heat-sealable layer was separately extruded onto the solidified coating layer.

[0361] Experiment 10b Similarly, when EC-LLDPE was blended with LDPE and the quality of the resulting planar coating layer was investigated, it was found that there was almost no difference when blended with LDPE, and a slight difference may occur when blended at 50% by weight. Therefore, in order to obtain the best possible performance from the EC-LLDPE polymer, it is recommended to avoid blending with LDPE, as can be inferred from Figure 16b.

[0362] Experiment 11 Figure 17a shows that the inner polymer multilayer section has a total basis weight of 26 g / m². 2 This figure shows the results of further tests performed using poroscopy on flat, unfolded laminated materials without creases or folds. Sample PM 12077, which had a polymer with a two-stage extrusion coating on the inner surface and used 100% HDPE RigidexFA from Ineos as the intermediate layer, had a higher frequency of dielectric breakdown than sample PM12104, which had a two-stage extrusion coating layer and used a blend of 50 wt% HDPE and 50 wt% LDPE as the intermediate layer.

[0363] Since no similar tests were conducted on the method of two-stage extrusion coating of the inner polymer in a three-layer structure with the selected EC-LLDPE as the intermediate layer, it was not possible to verify whether further improvements could be obtained by using EC-LLDPE, which has load-bearing and distribution functions. However, considering the findings obtained from the corresponding two-stage extrusion coating of the inner surface containing HDPE as the intermediate layer, and the corresponding two-stage co-extrusion coating of the conventional inner surface (i.e., having only the EAA adhesion promoting layer and the "mPE" heat-sealing blend layer), it is considered highly probable. In the laminated material shown in Figure 17b, interlayer integrity test results for different types of flat, unfolded inner polymer layers clearly showed that the two-stage extrusion coating method was superior to the single co-extrusion coating method. The basis weight of the inner polymer multilayer shown in Figure 17b is approximately 26 g / m². 2 However, in the third sample (PM12225), the basis weight was 35 g / m². 2 That was the case.

[0364] Experiment 12 Figure 18 shows that in a two-stage extrusion coating of the inner polymer layer, in the high-voltage "Holiday" test described in Experiment 6, when HDPE polymer is blended with 50% by weight LDPE, the intermediate layer made of Ineos HDPE RigidexFA exhibits superior performance during biaxial bending and unfolding compared to a layer made of 100% by weight HDPE.

[0365] This means that, on average, a 100 wt% HDPE sample fractured at half the total thickness of the inner polymer layer compared to a blend of HDPE with 50 wt% LDPE. Therefore, blending HDPE and LDPE resulted in a remarkable improvement of approximately 100%.

[0366] In this comparative measurement, the laminated sample had a thinner inner polymer layer structure (approximately 26 g / m²). 2 It has ), which makes dielectric breakdown more easily induced. The two-stage extruded coating laminate is approximately 35 g / m². 2Naturally, performance will improve further at higher overall thicknesses.

[0367] In a comparison with a comparative laminated sample having an inner layer structure blended with mLLDPE and LDPE, it was shown that blending HDPE slightly surpassed the level of the comparative sample in terms of inner layer integrity performance during biaxial bending.

[0368] Therefore, the performance of the packaging laminate in terms of simple bending strength is remarkably improved by the extruded-coated polymer inner layer configuration containing HDPE as an intermediate layer compared to a layer configuration having only mLLDPE polymer of the same weight. In biaxial bending, the HDPE-containing inner layer polymer configuration shows superior performance when HDPE is blended with LDPE. Furthermore, processing the inner layer containing HDPE as a load-bearing layer with a two-stage extrude coating reduces the number of weak points and defects on the planar polymer layer, thereby improving the integrity of the layer.

[0369] From these findings, it is shown that HDPE or MDPE are particularly suitable materials for the inner polymer structure of paper barrier laminates, providing superior OTR fold rigidity compared to inner polymers made of pre-fabricated cast LLDPE film, and further blending HDPE and LDPE improves integrity during folding. At the same time, compared to using pre-fabricated LLDPE film for the inner layer polymer, using only extruded coated polymer layers in the inner polymer multilayer significantly improves the overall openability of the packaging material. Therefore, a more load-bearing inner polymer multilayer provides robustness to laminated carton-based packaging materials using barrier-coated cellulose sheets or films as the substrate. In particular, a more robust inner multilayer is required when using inferior paper substrates that have low flexibility and are prone to cracking of the thin barrier coating due to damage to the cellulose fiber material when the paper is folded.

[0370] The structure of the laminated packaging material according to the present invention has been demonstrated to be a highly cost-effective solution that maintains excellent OTR properties even after the material has been folded into a package. Furthermore, the inner polymer multilayer itself remains intact without thinning of the polymer layer or other defects, and withstands bending forces, thus better protecting sensitive contents in the filled packaging container. Because the inner multilayer is not damaged, the thin barrier coating also remains undamaged and can continue to perform its intended purpose.

[0371] In this way, the improved laminated packaging material can withstand bending and molding into a packaging container, protecting oxygen-sensitive liquids, fluids, and viscous foods while maintaining sterility during storage.

[0372] Furthermore, these laminated packaging materials, which have a cellulose-based barrier coating structure instead of aluminum foil or thick polymer barrier materials, also offer improved repulping and recyclability after use, meeting the future needs for environmentally sustainable laminated packaging materials.

[0373] Furthermore, a laminated packaging material with improved heat sealing properties is provided, which does not contain aluminum foil but offers good gas barrier and other barrier properties, while reasonably keeping the cost and complexity of raw materials and manufacturing processes down, making it suitable for long-term sterile packaging.

[0374] In a preferred embodiment in which the inner polymer multilayer is extruded and coated in two stages, the integrity of the inner polymer multilayer is also broadly and further enhanced throughout the entire planar direction of the laminated packaging material.

[0375] Conclusions from Experiments 3b, 4b, 8b, 9b, and 10b of the present invention Beyond the subject matter obtained from the above experiments 3a, 4a, 5, 6, 7, 8a, 9a, 10a, 11 and 12, further embodiments of the present invention have been realized, as demonstrated by the above experiments 3b, 4b, 8b, 9b and 10b.

[0376] From Experiment 3b, it can be concluded that a good packaging container can be obtained from the laminated material of the present invention. This packaging container exhibits a package OTR value equivalent to that of a corresponding laminated material having an internal polymer multilayer structure with HDPE as the load-bearing layer, and is similarly improved compared to a corresponding laminated material having a conventional internal polymer structure.

[0377] As is clear from Experiment 4b, the OTR results regarding robustness when the selected EC-LLDPE is used as the intermediate inner layer are significantly better than the conventional inner polymer configuration consisting only of an adhesive polymer layer and a low-temperature heat-sealable polymer layer. However, it does not match the comparative inner polymer multilayer configuration in Experiment 4a, which uses HDPE as the load-bearing layer. Furthermore, a slight improvement can be observed by blending EC-LLDPE for load bearing and load distribution with LDPE.

[0378] From Experiment 8b, it can be concluded that the laminate of the present invention exhibits significantly superior performance in biaxial bending compared to similar laminates having a load-bearing layer containing an arbitrary proportion of HDPE as an intermediate layer in an internal polymer multilayer structure. From Figure 14c, it can be concluded that mixing EC-LLDPE and LDPE is not beneficial from this perspective. Although the extruded coating layer of EC-LLDPE, which has a high melting point, is considered to have lower load-bearing capacity than the HDPE polymer, it still exhibits superior performance due to its excellent load distribution characteristics, as the polymer is deformed without weakening during the biaxial bending step.

[0379] Experiments 9b and 10b confirm that the unfolded laminate of the planar surface constituting the load-supporting and load-distributing interior made of the EC-LLDPE layer of the present invention also exhibits superior quality compared to the corresponding laminate having an HDPE layer. While there may be some slight advantages to blending LLDPE and LDPE in this respect as well, these advantages do not outweigh the advantages of not blending, as seen with respect to the biaxial bending performance demonstrated in Experiment 8b. Furthermore, based on studies that have yielded good properties in concurrently pending subjects, it is believed that the laminated material of the present invention, including the EC-LLDPE inner intermediate layer, can be further improved by extruding the inner layers separately in at least two extrusion coating steps, allowing the previous layer to solidify before coating the next layer.

[0380] The laminate of the present invention has only an extruded polymer layer in its inner polymer multilayer structure, and therefore has good openability, which is significantly better than when a pre-fabricated film is laminated to the inner multilayer portion of the laminate.

[0381] Therefore, a sufficiently functional alternative configuration, or a configuration with even better functionality, is provided for the inner polymer multilayer in a heat-sealable and liquid-tight laminated carton-based packaging material having a non-aluminum foil / paper-based barrier structure. The inner polymer multilayer described in the present invention not only improves the integrity of the laminate layer but also improves load-bearing and load-distributing properties during folding formation in a better manner, and provides an excellent way to protect and integrate such paper-based barrier material in a laminated carton-based packaging material.

[0382] Finally, it should be added that the present invention is not limited to the embodiments shown and described above, and various modifications may be made within the scope of the claims.

Claims

1. A barrier-coated cellulose fiber substrate (10a; 10b) used as an oxygen barrier for materials in heat-sealable laminated containers for oxygen-sensitive foods such as liquid foods, Basis weight 30-80g / m ２ , density 700-900kg / m ３ The system comprises a fibrous cellulose substrate (11) of less than 100 mm, and a first gas barrier coating (13) applied to the first surface of the fibrous cellulose substrate by dispersion or solution coating of an aqueous oxygen barrier composition and subsequent evaporation drying. The barrier-coated cellulose fiber substrate (10a; 10b) further comprises a steam-resistant base coat (12) located beneath the first gas barrier coating and directly adjacent to and in contact with the first surface of the fibrous cellulose substrate (11) coated with an aqueous dispersion coating, thereby imparting gas barrier properties to the heat-sealable laminated packaging material. Barrier-coated cellulose fiber substrates (10a; 10b).

2. The fibrous cellulose substrate (11) has a density of 700 to 850 kg / m³ ３ For example, 700-830 kg / m ３ For example, 700-800 kg / m ３ That is, A barrier-coated cellulose fiber substrate (10a; 10b) according to claim 1.

3. The fibrous cellulose substrate (11) is essentially made from kraft pulp fibers. A barrier-coated cellulose fiber substrate (10a; 10b) according to claim 1 or 2.

4. The steam-resistant base coating (12) comprises 30 to 96% by weight, for example 40 to 96% by weight, for example 50 to 96% by weight, for example 55 to 96% by weight, for example 60 to 96% by weight, for example 65 to 96% by weight, for example 70 to 96% by weight, inorganic particles, 4 to 70% by weight, for example 4 to 60% by weight, for example 4 to 50% by weight, for example 4 to 45% by weight, for example 4 to 40% by weight, for example 4 to 35% by weight, for example 4 to 30% by weight, a polymer binder, and other additives. A barrier-coated cellulose fiber substrate (10a; 10b) according to any one of claims 1 to 3.

5. The steam-resistant base coating (12) is formed by an aqueous dispersion coating and has a dry weight of 5 to 25 g / m ２ , for example, 7 to 22 g / m ２ , for example, 7 to 20 g / m ２ , for example, 7 to 19 g / m ２ , for example, 10 to 20 g / m ２ , for example, 10 to 19 g / m ２ and is A barrier-coated cellulose fiber substrate (10a; 10b) according to any one of claims 1 to 4.

6. The polymer binder of the steam-resistant coating (12) is an aqueous emulsion binder selected from the group consisting of acrylic or methacrylic homopolymer or copolymer aqueous emulsions, such as styrene-acrylate latex, vinyl acrylic copolymer latex, or vinyl acetate acrylate copolymer latex, as well as styrene-butadiene copolymers, such as styrene-butadiene latex, as well as bio-based emulsion binders, such as modified starch latex, as well as vinyl alcohol polymers, such as polyvinyl alcohol (PVOH) or ethylene vinyl alcohol (EVOH), and other modified starch or starch derivatives. A barrier-coated cellulose fiber substrate (10a; 10b) according to any one of claims 1 to 5.

7. The surface roughness of the dried and uncoated free surface of the steam-resistant substrate coating (12) is less than 150 ml / min Bendtsen, for example less than 100 ml / min Bendtsen, for example less than 80 ml / min Bendtsen, for example less than 50 ml / min Bendtsen. A barrier-coated cellulose fiber substrate (10a; 10b) according to any one of claims 1 to 6.

8. The aqueous oxygen barrier composition of the first gas barrier coating (13) comprises a polymer selected from the group consisting of starch and vinyl alcohol polymers and copolymers, for example, a polymer selected from the group consisting of polyvinyl alcohol (PVOH), ethylene vinyl alcohol (EVOH), and starch. A barrier-coated cellulose fiber substrate (10a; 10b) according to any one of claims 1 to 7.

9. The first gas barrier coating (13) is applied by aqueous dispersion or solution coating at a dry weight of 0.5 to 4 g / m². ２ For example, 0.5 to 3 g / m ２ For example, 0.5 to 2 g / m ２ It is applied with A barrier-coated cellulose fiber substrate (10a; 10b) according to any one of claims 1 to 8.

10. The invention comprises at least one further gas barrier coating coated on the first gas barrier coating, the at least one further gas barrier coating comprising at least one barrier deposition coating (14) coated by vapor deposition, thereby providing the barrier-coated fibrous cellulose substrate (10b) with gas barrier properties and water vapor barrier properties in a heat-sealable laminated packaging material. A barrier-coated cellulose fiber substrate (10a; 10b) according to any one of claims 1 to 9.

11. The barrier deposition coating (14) is a vapor deposition coating of a material selected from metals, metal oxides, inorganic oxides, and carbon. A barrier-coated cellulose fiber substrate (10a; 10b) according to claim 10.

12. The barrier deposition coating (14) is a vapor deposition coating selected from the group consisting of aluminum and aluminum oxide (AlOx), and is preferably an aluminum vapor deposition coating. A barrier-coated cellulose fiber substrate (10a; 10b) according to claim 10 or 11.

13. A heat-sealable laminated packaging material (10c; 20a; 20b; 20c; 20d), A barrier-coated cellulose fiber substrate (10a; 10b; 25a; 25b; 25c; 25d) according to any one of claims 1 to 12, further comprising a first outermost protective material layer (15; 22a; 22b; 22c; 22d) and a second innermost liquid-tight and heat-sealable material layer (16; 23a; 23b; 23b'; 23c; 23d), Heat-sealable laminated packaging material (10c; 20a; 20b; 20c; 20d).

14. The second innermost liquid-tight and heat-sealable material layer (16; 23a; 23b; 23b'; 23c; 23d) comprises a polymer selected from the group consisting of polyolefin polymers, such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and blends thereof. The heat-sealable laminated packaging material (20d) according to claim 13.

15. The invention comprises a bulk layer (21a; 21b; 21c; 21d) of paper, cardboard, or other cellulose-based material, wherein the barrier-coated cellulose fiber substrate (10a; 10b; 25a; 25b; 25c; 25d) is disposed inside the bulk layer of the paper or cardboard and between the bulk layer and the second innermost liquid-tight and heat-sealable material layer (16; 23a; 23b; 23b'; 23c; 23d). The heat-sealable laminated packaging material (20d) according to claim 13 or 14.

16. The barrier-coated cellulosic fiber substrate (10a; 10b; 25b; 25c; 25d) is bonded to the substrate layers (21a, 21b; 21c; 21d) via an intermediate adhesive layer (26b; 26c; 26d-1), wherein the intermediate adhesive layer comprises a composition containing a binder selected from the group consisting of acrylic polymers and copolymers, starch, cellulose and polysaccharide derivatives, vinyl acetate and / or vinyl alcohol polymers and copolymers. The heat-sealable laminated packaging material (20d) according to claim 15.

17. The second innermost liquid-tight and heat-sealable material layer (23a'; 23b'; 23c') is a pre-made film made of polyolefin, or is contained in a pre-made film, in order to improve the robustness of the mechanical properties of the packaging material. A heat-sealable laminated packaging material (20d) according to any one of claims 13 to 16.

18. The packaging container has an inner polymer multilayer portion in which all polymer layers are applied on a barrier-coated cellulose fiber substrate, and includes a second innermost liquid-tight and heat-sealable material layer (23d) that is in direct contact with the product filled in the packaging container made from a packaging material containing high-density polyethylene (HDPE), medium-density polyethylene (MDPE), or linear low-density polyethylene with a melting point exceeding 115°C at a melt flow rate (MFR) of 4 to 20 g / 10 min (190°C / 2.16 kg), all of which layers of the inner polymer multilayer portion are formed by extrusion coating on the inner surface of the barrier-coated cellulose fiber substrate, and the second innermost liquid-tight and heat-sealable layer is a low-density polyethylene selected from the group consisting of, for example, low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and blends thereof. A heat-sealable laminated packaging material (20d) according to any one of claims 13 to 16.

19. The main melting point peak, Tm, of the second innermost liquid-tight and heat-sealable material layer (23d) is 88 to 110°C. A heat-sealable laminated packaging material (20d) according to any one of claims 13 to 16 or 18.

20. The intermediate load-bearing layer (28d) comprises a polymer blend composition containing 30 to 90% by weight of HDPE or MDPE and 10 to 70% by weight of LDPE, preferably 50 to 80% by weight of HDPE or MDPE and 20 to 50% by weight of LDPE. The heat-sealable laminated packaging material (20d) according to claim 18 or 19.

21. The intermediate load-bearing layer (28d) may, as an alternative, contain a polymer blend comprising 50 to 95% by weight of LLDPE having a melt flow rate of 4 to 20 g / 10 min (190°C / 2.16 kg) and a melting point exceeding 115°C, and 5 to 50% by weight of HDPE or MDPE. The heat-sealable laminated packaging material (20d) according to claim 18 or 19.

22. The basis weight of the aforementioned intermediate load-bearing layer (28d) is 8 to 25 g / m². ２ For example, 10-25 g / m ２ For example, 12-25 g / m ２ For example, 15-25 g / m ２ For example, 15-20 g / m ２ That is, A heat-sealable laminated packaging material (20d) according to any one of claims 18 to 21.

23. The inner polymer multilayer portion further includes a binding layer (24d) containing an adhesive polymer that is adjacent to and in contact with the barrier-coated inner surface of the cellulose fiber substrate (25d). A heat-sealable laminated packaging material (20d) according to any one of claims 18 to 22.

24. A packaging container (50a; 50b; 50c; 50d) comprising a heat-sealable laminated packaging material (10c; 20a; 20b; 20c; 20d) according to any one of claims 13 to 23.

25. A method for producing a barrier-coated cellulose fiber substrate (10a; 10b; 25a; 25b; 25c; 25d) according to any one of claims 1 to 12, A first step is to supply a fibrous cellulose substrate having a mechanically polished or mechanically finished surface as a moving web (31a) in a roll-to-roll system, A second step involves dispersing (32a) a vapor-resistant base coating dispersion composition containing 25-96% by weight of inorganic particles and 4-75% by weight of polymer binder on a moving fibrous cellulose substrate (31a), and then drying (33a) the applied base coating by forced evaporation. A third step involves performing a smoothing treatment, such as soft calendering, on the surface of the base-coated fibrous cellulose substrate obtained from the second step, A fourth step involves dispersing (32a') an aqueous second dispersion or solution of the first gas barrier coating composition onto a smoothed base-coated fibrous cellulose substrate (31a') in transit, and then drying (33a') the applied first gas barrier coating by forced evaporation. Optionally, repeat step 4 one or more times. As an option, a fifth step is to deposit an additional barrier coating by vapor deposition (40) onto the free surface of the first gas barrier coating on the moving gas barrier coated fibrous cellulose substrate (41-43), Methods that include...

26. The steam-resistant substrate coating composition (12) is an aqueous composition containing 10 to 20% by weight of a polymer binder and 80 to 90% by weight of inorganic particles, by dry weight. The method according to claim 25.

27. The surface roughness of the steam-resistant base coating (12) on the uncoated fibrous cellulose substrate obtained from the third step is measured according to ISO 8791-4 (PPS) to be less than 3 μm, for example less than 2.5 μm, for example 2 μm or less, for example 1.5 μm or less, for example 1.2 μm or less, for example 1.0 μm or less. The method according to claim 25 or 26.

28. The uncoated free surface of the vapor-resistant base coating (12) applied to the substrate obtained from the second or third step has a Gurley air permeability resistance of 1500 seconds / 100 ml or more. The method according to any one of claims 25 to 27.

29. The initial method step is, alternatively, to provide the base-coated and smoothed fibrous cellulose substrate obtained from the first, second, and third steps as a moving web in a roll-to-roll system, and the subsequent next step is the same as the fourth step, and optionally, the next subsequent step is the same as the fifth step, in this order. The method according to any one of claims 25 to 28.

30. A method (30a; 30b, 30c) for producing a heat-sealable laminated packaging material (20d) according to any one of claims 18 to 23, The steps include laminating a barrier-coated cellulose fiber substrate (25d) onto a bulk layer (21d) of paper, cardboard, or other cellulose material (30a; 30b), The process involves a step (30c) of melt-extrude coating (30c) a first outermost protective material layer or coating (33d; 22d) that is on the outside of the packaging container formed from laminated packaging material onto the outer surface of the bulk layer (21d; 31b; 35), Steps (34d; 29d) of extruding and coating the inner polymer multilayer portion, Steps include: extruding and coating an inner polymer multilayer portion onto the inside of a barrier-coated cellulose fiber substrate, which includes a second innermost liquid-tight and heat-sealable material layer (23d) that is in direct contact with the product filled in a packaging container made from packaging material, and an intermediate load-bearing layer (28d) containing high-density polyethylene, MDPE, or linear low-density polyethylene with a melt flow rate of 4 to 20 g / 10 min (190°C / 2.16 kg) and a melting point exceeding 115°C, The second innermost liquid-tight and heat-sealable material layer contains low-density polyethylene selected from the group consisting of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and mixtures thereof. Method (30a; 30b, 30c).

31. The inner polymer multilayer portion (29d) is coated as separate layers in at least two consecutive steps by melt extrusion coating, and the previous melt extrusion coating layers (24d, 28d) are at least partially solidified before the next melt extrusion layer (23d) is coated on the previous layer. The method according to claim 30.

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