Method for manufacturing a paperboard-based packaging laminate

Abstract

The present invention relates to a method for manufacturing a paperboard-based packaging laminate. The method comprises: a) providing a paperboard-based layer; b) providing a vacuum-coated film layer; c) applying an adhesive composition to the paperboard-based layer and / or the vacuum-coated film layer; d) using the adhesive composition of a press nip to laminate the surface of the paperboard-based layer onto the surface of the vacuum-coated film layer such that the adhesive composition forms an adhesive bonding layer between the paperboard-based layer and the vacuum-coated film layer to form a laminate, wherein the position of the press nip is adjusted in a direction perpendicular to the lamination plane during lamination to correct for changes in the curl of the formed laminate.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a paperboard-based packaging material. More particularly, the present disclosure relates to the manufacture of a paperboard-based packaging laminate comprising a vacuum-coated film layer.

Background Art

[0002] Coating paperboard with plastic is often used to combine the mechanical properties of paperboard with the barrier and sealing properties of plastic film. Even in relatively small amounts, adding an appropriate plastic material to paperboard can provide the properties necessary for the manufacture of paperboard suitable for many demanding applications, such as liquid or food packaging cartons. In liquid or food packaging cartons, polyolefin coatings are frequently used as liquid barrier layers, heat seal layers, and adhesives. However, recycling such polymer-coated paperboard is difficult because it is difficult to separate the polymer from the fibers.

[0003] Also, in many cases, the water vapor barrier properties of polymer-coated paperboard are still insufficient unless the coating layer is thick or a combination of different polymer coating layers is used. Therefore, to ensure high water vapor barrier properties, polymer-coated paperboard is often combined with one or more layers of aluminum foil. However, adding polymers and aluminum foil significantly increases the cost, and the combination of the polymer coating layer and aluminum foil makes material recycling more difficult. Also, because of its large carbon footprint, it is desirable to replace aluminum foil with paperboard-based packaging materials.

[0004] The aseptic packaging of long-term storable products such as milk and juice is usually made of thick paper for liquid or food packaging, including a multi-layer paper-based substrate, an outermost layer of heat-sealable polyolefin (e.g., polyethylene, PE), and an innermost layer of polyolefin and aluminum. The aluminum foil layer necessary to provide water vapor and oxygen barrier properties is usually incorporated between the layers of polyethylene to provide a structure of PE / paper / PE / aluminum / PE.

[0005] In the prior art, attempts have been made to replace aluminum foil with more environmentally friendly and / or recyclable solutions, but so far, they have not been actually successful. For example, microfibrillated cellulose (MFC) films and coatings have been developed in which fibrillated cellulose fibers and microfibrils are dispersed, for example, in water and then reorganized and recombined to form high-density films or coatings with excellent gas barrier properties. Unfortunately, the water vapor and gas barrier properties of such MFC films tend to deteriorate at high humidity.

[0006] One of the solutions discussed in the prior art is to directly deposit a thin vacuum coating layer on the substrate using, for example, chemical vapor deposition or physical vapor deposition methods. The thin vacuum coating layer may include, for example, a thin layer of aluminum, Al2O3, AlOx, or SiOx. The problem with these deposition methods is that the coating process is carried out under vacuum, which means that the substrate needs to be degassed. In the case of paper, especially thick and low-density paper, this means that the process is costly, but it also means that the substrate is dried to a very low water content by degassing. By drying and then rehumidifying to the ambient moisture level, the mechanical properties of the paper change. Drying not only increases the tendency of the paper to crack and its post-processability but also poses a significant risk of cracking in the thin and sensitive vacuum coating layer when the substrate is re-wetted.

[0007] Also, instead of aluminum foil, it has been proposed to use metallized polymers or cellulose-based films laminated to a paperboard-based substrate by an adhesive bonding layer, such as metallized polyethylene or polypropylene films. The adhesive bonding layer can be applied in a molten state, for example, by extrusion coating, or in the form of an aqueous solution or dispersion using a liquid coating method.

[0008] The problem with metallized films is that the thin metallized layer is sensitive to the operation of the substrate film on which it is applied and the operation of the finished laminate, and cracks or pinholes can occur in the metallization.

[0009] When high temperatures are applied to the lamination process when the bonding layer or heat seal layer is extruded, the metallized polymer or cellulose-based film may be stretched (expanded) and then shrink upon cooling, which can cause pinholes and cracks in the thin and sensitive metallized layer and adversely affect the gas barrier properties of the laminate.

[0010] The problem with laminating a metallized film to paperboard using an aqueous adhesive is that the large amount of water applied with the adhesive can cause the paperboard-based substrate to become wet and cause web curl.

[0011] Therefore, there is still a need for an improved solution to replace the combination of plastic film and aluminum foil in paperboard-based packaging materials while maintaining acceptable liquid and oxygen barrier properties. At the same time, it is necessary to replace the combination of plastic film and aluminum foil with alternatives that facilitate the repulping and recycling of used packaging materials. SUMMARY OF THE INVENTION

[0012] The object of the present disclosure is to provide an alternative method for manufacturing a paperboard-based packaging laminate, such as paperboard for liquid or food packaging, that provides good water vapor barrier properties even at higher relative humidity and temperature.

[0013] A further object of the present disclosure is to provide an alternative method for manufacturing a paperboard-based packaging laminate comprising a vacuum-coated film layer, which overcomes at least some of the problems such as web curl and / or pinhole formation, or cracking of the thin and sensitive vacuum coating layer associated with conventional manufacturing methods.

[0014] A further object of the present disclosure is to provide an alternative method for manufacturing a paperboard-based packaging laminate having a water vapor transmission rate (WVTR) of less than 30 cc / m 2 / 24 h, measured in accordance with ASTM standard F1249-20 at 50% relative humidity and 23 °C.

[0015] The above-described objects, as well as other objects that will be realized by those skilled in the art in light of the present disclosure, are achieved by various aspects of the present disclosure.

[0016] The present invention is based on the understanding that a very thin coating layer, typically in the range of 20 to 600 nm, more preferably in the range of 5 to 250 nm, formed by a vacuum coating process such as physical vapor deposition (PVD) or chemical vapor deposition (CVD), can provide good oxygen and water vapor barrier properties comparable to those of thick aluminum foil. Since the thickness of the vacuum coating layer is usually at least one order of magnitude thinner than that of conventional foils, the metal content of the product can be significantly reduced.

[0017] However, it has been found that so-called direct vacuum coating, which is carried out directly on the substrate to be vacuum-coated, has problems with thick and low-density paperboard-based layers. Also, when a vacuum-coated film is laminated to a paperboard-based layer, the web often curls and / or pinholes or cracks form in the thin and sensitive vacuum coating layer.

[0018] The present invention is based on the recognition that at least some of these problems can be overcome by performing lamination using a press nip whose position can be adjusted in a direction perpendicular to at least the lamination surface with respect to the web surface during lamination. In other words, the position of the press nip can be adjusted in a direction perpendicular to the lamination surface during lamination.

[0019] According to a first aspect shown herein, a method of manufacturing a paperboard-based packaging laminate, a) providing a paperboard-based layer, b) providing a vacuum-coated film layer, c) applying an adhesive composition to the paperboard-based layer and / or the vacuum-coated film layer, d) laminating the surface of the paperboard-based layer to the surface of the vacuum-coated film layer using the adhesive composition in a press nip such that the adhesive composition forms an adhesive bond layer between the paperboard-based layer and the vacuum-coated film layer to form a laminate comprising, wherein the position of the press nip is adjusted in a direction perpendicular to the lamination surface during lamination to correct for changes in curl of the formed laminate, a method is provided.

[0020] Paperboard generally refers to strong and thick paper or cardboard containing cellulose fibers used for boxes and other types of packaging. Paperboard can be manufactured in various thicknesses, either bleached or unbleached, coated or uncoated, depending on the requirements of the end use. Paperboard can be a single layer of material or a multi-layer material composed of two or more layers. A common type of multi-layer paperboard is composed of a low-density intermediate layer (sometimes called "bulk ply") sandwiched between two high-density outer layers. The low-density intermediate layer typically has a density of less than 750 kg / m 3 less than, preferably less than 700, less than 650, less than 600, less than 550, less than 500, less than 450, less than 40(), or less than 350 kg / m 3It may have a lower density. The high-density outer layer typically has a density at least 100 kg / m less than that of the intermediate layer 3 higher, preferably at least 200 kg / m higher than the density of the intermediate layer 3 and has a high density.

[0021] The paperboard-based packaging laminate is a packaging material mainly formed from a paperboard-based layer. The paperboard-based layer can be manufactured from pulp containing fibers from virgin fibers, such as mechanical pulp, chemical pulp, and / or thermomechanical pulp. It can also be manufactured from broken paper or recycled paper. In some embodiments, the paperboard-based layer is so-called double or triple paperboard. In addition to the paperboard-based layer, the paperboard-based packaging laminate may include additional layers or coatings designed to improve the performance and / or appearance of the packaging laminate.

[0022] The paperboard-based packaging laminate typically has a first outermost surface intended to function as the outer or printed surface and a second outermost surface intended to function as the inner surface of the packaging container. It is preferred that one side of the paperboard-based layer including the vacuum coating layer is intended to function as the inner surface of the packaging container.

[0023] The paperboard-based packaging laminate obtained by the method of the present invention can provide both excellent water vapor barrier properties and liquid barrier properties. Particularly useful are the high water vapor barrier properties at high humidity and high temperature enabled by the vacuum-coated film layer. The term high humidity in the context of the present disclosure generally refers to a relative humidity (RH) of 50% or more. The term high temperature in the context of the present disclosure generally refers to a temperature of 23°C or more. The water vapor barrier properties of the packaging laminate at high humidity and temperature are usually measured at a typical relative humidity (RH) of 50% and a temperature of 23°C. By the method of the present invention, a paperboard-based packaging laminate having a water vapor transmission rate (WVTR) of less than 30 cc / m 2 / 24 h can be obtained when measured in accordance with ASTM standard F1249-20 at a relative humidity of 50% and a temperature of 23°C.

[0024] The method of the present invention is particularly useful for the manufacture of paperboard-based packaging laminates comprising a thick, low-density paperboard base layer. The paperboard base layer used in the method of the present invention typically has a basis weight in the range of at least 100 g / m 2 , preferably 100 to 1000 g / m 2 and is a relatively thick paperboard. The density of the paperboard base layer is typically less than 800 kg / m 3 . The bending resistance of the paperboard base layer measured in the machine direction in accordance with ISO 2493 (L&W, 15°) can typically exceed 80 mN.

[0025] The paperboard base layer can be heavier. In some embodiments, the paperboard base layer has a basis weight of at least 150 g / m 2 , 200 g / m 2 , 250 g / m 2 , 300 g / m 2 , 350 g / m 2 , or 400 g / m 2 . The basis weight of the paperboard base layer is preferably less than 1000 g / m 2 , 800 g / m 2 , or 600 g / m 2 . Unless otherwise specified, the basis weight is determined in accordance with ISO standard 536.

[0026] In some embodiments, the paperboard base layer has a density of less than 700 kg / m 3 , preferably less than 600 kg / m 3 . Unless otherwise specified, the density is determined in accordance with ISO standard 534.

[0027] In some embodiments, the bending resistance of the paperboard base layer in the machine direction (MD) measured in accordance with ISO 2493 (L&W, 15°) is greater than 90 mN, preferably greater than 100 mN.

[0028] In some embodiments, the bending resistance of the paperboard base layer in the cross machine direction (CD) measured in accordance with ISO 2493 (L&W, 15°) is greater than 40 mN, preferably greater than 45 mN.

[0029] In some embodiments, the paperboard base layer has a bending resistance index of at least 1.3, preferably at least 1.5, as measured in accordance with ISO 2493-2. In some embodiments, the paperboard base layer has a bending resistance index of at least 1.7, as measured in accordance with ISO 2493-2.

[0030] The paperboard base layer can be single-ply paperboard or multi-ply paperboard. In some embodiments, the paperboard base layer is multi-ply paperboard. In some embodiments, the paperboard base layer is multi-ply paperboard consisting of two or more plies. In some embodiments, the paperboard base layer is multi-ply paperboard consisting of three or more plies. In some embodiments, the paperboard base layer is multi-ply paperboard consisting of a low-density intermediate ply sandwiched between two high-density outer plies.

[0031] In some embodiments, the paperboard base layer includes foamed paperboard. In some embodiments, the paperboard base layer is foamed paperboard. In some embodiments where the paperboard base layer is multi-ply paperboard, at least one ply, preferably the intermediate ply, is foamed.

[0032] The structure of the paperboard-based packaging laminate of the present invention allows for the use of a large amount of recycled fibers in the paperboard base layer because the barrier structure prevents the movement of undesirable contaminants such as mineral oil-based compounds. Thus, in some embodiments, the paperboard base layer includes at least 5 wt% recycled fibers, preferably at least 10 wt% recycled fibers.

[0033] In some embodiments, the paperboard base layer further includes a mineral coating layer on one or both of the main surfaces.

[0034] In some embodiments, the mineral coating layer, based on the total dry weight of the mineral coating layer, contains 50 to 95 wt% particulate mineral, and 5 to 50 wt% binder and.

[0035] In some embodiments, the mineral coating layer comprises 65 to 95 wt% particulate mineral and 5 to 35 wt% binder. In some embodiments, the mineral coating layer comprises 80 to 94 wt% particulate mineral and 6 to 20 wt% binder. In some embodiments, the mineral coating layer comprises 86 to 94 wt% particulate mineral and 6 to 14 wt% binder.

[0036] In some embodiments, the particulate mineral is selected from the group consisting of kaolin, calcium carbonate, bentonite, talc, and combinations thereof, preferably from the group consisting of kaolin or calcium carbonate, and more preferably kaolin.

[0037] The binder may include a single binder or a combination of binders. The binder may preferably include a water-dispersible or water-soluble binder, or a combination thereof. In some embodiments, the water-dispersible binder may include a latex binder. In some embodiments, the water-soluble binders include starch or starch derivatives, PVOH or its modified forms, CMC, proteins, or cellulose derivatives such as seaweed. The advantage of using a water-soluble binder is that the recycling of the laminate becomes easier.

[0038] In some embodiments, the basis weight of the mineral coating layer is in the range of 4 to 30 g / m 2 and more preferably in the range of 6 to 14 g / m 2 .

[0039] The mineral coating layer can preferably be applied in at least two different coating steps while drying the coated film between each step. The mineral coating layer can also preferably be calendared with a soft calender or a belt calender.

[0040] In some embodiments, the packaging laminate is further provided with a barrier coating layer for improving the gas barrier properties of the laminate, particularly the oxygen barrier properties. The barrier coating layer is preferably disposed between the paperboard base layer and the vacuum-coated film layer. In some embodiments, the barrier coating layer is in direct contact with the base layer.

[0041] The barrier coating layer is preferably soluble in cold water or water-soluble after heating at a temperature below 100 °C for a given fixed time. The water solubility of the barrier coating layer improves the separation of the vacuum-coated film layer from the base layer during repulping.

[0042] In some embodiments, the barrier coating layer comprises a polymer selected from the group consisting of polyvinyl alcohol (PVOH), copolymers of ethylene and polyvinyl alcohol, starch, carboxymethyl cellulose, and combinations thereof. In some embodiments, the polymer of the barrier coating layer is PVOH.

[0043] PVOH can have a degree of hydrolysis in the range of, for example, 80 to 99 mol%, preferably in the range of 85 to 98 mol%. The crystallinity of PVOH, determined by wide-angle X-ray scattering, is preferably less than 0.6, preferably less than 0.5, more preferably less than 0.4.

[0044] In some embodiments, the barrier coating layer comprises at least 50 wt% PVOH, preferably at least 70 wt% PVOH, based on the total dry weight of the barrier coating layer.

[0045] PVOH may be unmodified PVOH or modified PVOH. Modified PVOH may preferably be ethylene-modified PVOH.

[0046] To minimize the risk of pinholes occurring in the barrier coating layer, the barrier coating layer can preferably be applied in at least two different coating steps while drying the coated film between steps.

[0047] The barrier coating layer is preferably formed in the form of an aqueous solution or dispersion by a liquid film coating process, i.e., spread onto the substrate as a thin, uniform layer upon application and then dried. The barrier coating layer can be applied by a contact coating or non-contact coating method. Examples of useful coating methods include, but are not limited to, rod coating, curtain coating, film press coating, cast coating, transfer coating, size press coating, flexographic coating, gate roll coating, twin roll HSM coating, blade coating (e.g., short time blade coating), jet applicator coating, spray coating, gravure coating, or reverse gravure coating.

[0048] In some embodiments, at least one barrier coating layer is applied in foamed form. The foamed coating is advantageous because it can form a film with a higher solids content and a lower water content compared to an unfoamed coating. The low water content of the foamed coating also reduces the problem of rewetting of the paperboard-based layer. The foam can be formed using a polymeric or non-polymeric foaming agent. Examples of polymeric foaming agents include PVOH, hydrophobically modified starch, and hydrophobically modified ethyl hydroxyethyl cellulose.

[0049] In some embodiments, a crosslinking agent is added to the barrier coating layer. The crosslinking agent can improve the water resistance and adhesion of the barrier coating layer. Suitable crosslinking agents include, but are not limited to, glyoxal, citric acid, and glutaraldehyde. The concentration of the crosslinking agent can be, for example, 1 to 20 wt%, preferably 1 to 15 wt% based on the weight of the barrier coating layer.

[0050] In some embodiments, the barrier coating layer further contains water-insoluble particles in an amount less than 30 wt% based on the dry weight of the barrier coating layer. As used herein, the term water-insoluble means that the particles are insoluble in water at 23 °C and pH 7 - 8. In some embodiments, the water-insoluble particles are microfibrillated cellulose (MFC) or cellulose nanocrystals. In preferred embodiments, the coating of the barrier coating layer contains 70 - 100 wt% of PVOH and 30 - 0 wt% of MFC or cellulose nanocrystals. MFC or cellulose nanocrystals provide reinforcement and improve the mechanical properties of PVOH.

[0051] In some embodiments, the coating weight of the barrier coating layer ranges from 0.5 to 15 g / m 2 preferably in the range of 0.5 to 10 g / m 2 more preferably in the range of 1 to 8 g / m 2 even more preferably in the range of 2 to 6 g / m 2 is in the range.

[0052] In some embodiments, the barrier coating layer also functions as an adhesive bonding layer between the paperboard base layer and the vacuum-coated film layer.

[0053] In some embodiments, the paperboard base layer is subjected to plasma treatment, corona treatment, flame treatment, or steam treatment before lamination.

[0054] The PPS (Parker Print Surf) smoothness of the mineral coating layer conforming to ISO 8791-4 is preferably less than 5 μm, more preferably in the range of 0.3 to 4 μm. The Cobb-Unger value (30 s, bs) of the mineral coating layer is preferably less than 20 g / m 2 2, preferably in the range of 1 to 20 g / m 2 , more preferably in the range of 5 to 15 g / m 2 . Here, the Cobb-Unger value is a measure of oil absorption and is measured by the SCAN-P 37:77 (30 seconds) method.

[0055] The paper base layer before lamination typically has a high water vapor transmission rate (WVTR) value, i.e., insufficient water vapor transmission resistance. In some embodiments, the paper base layer has a water vapor transmission rate (WVTR) of more than 100 g / m 2 / 24 h, typically more than 200 g / m 2 / 24 h, more than 300 g / m 2 / 24 h, or more than 1000 g / m 2 / 24 h, as measured in accordance with ASTM standard F1249-20 at a relative humidity of 50% and 23°C.

[0056] A vacuum-coated film layer is laminated on the provided paper base layer using an adhesive composition. The surface of the paper base layer is laminated on the surface of the vacuum-coated film layer using the adhesive composition in a press nip so that the adhesive composition forms an adhesive bonding layer between the paper base layer and the vacuum-coated film layer.

[0057] The vacuum-coated film layer typically includes a vacuum coating layer formed on a substrate film.

[0058] As used herein, the term "film" generally refers to a thin, continuous sheet-forming material. The film may be a plastic film or a fiber-based film, and preferably can be formed from a highly purified fiber material, such as highly purified cellulose or microfibrillated cellulose. Depending on its composition, purpose, and properties, the film can also be regarded as thin paper or a membrane.

[0059] In some embodiments, the substrate film is a plastic film, preferably a film formed from polyethylene (PE), polypropylene (PP), or polyethylene terephthalate (PET).

[0060] In some embodiments, the substrate film is a fiber-based film, preferably a cellulose-based film. When the substrate film is a fiber-based film, the film is preferably formed from a highly purified fiber material.

[0061] In some embodiments, the substrate film is a thin, high-density paper such as kraft paper, greaseproof paper, glassine paper, tracing paper, translucent paper, transparent paper, roll paper, or parchment paper. The thin, high-density paper preferably has a basis weight in the range of 25-95 g / m 2 and a density greater than 800 kg / m 3 and more preferably greater than 900 kg / m 3 .

[0062] In a preferred embodiment, the substrate film is formed from microfibrillated cellulose (MFC).

[0063] In some embodiments where the substrate film is a fiber-based film, the substrate film may be surface-treated to improve the smoothness of the substrate surface, reduce porosity, and make the surface more suitable for vacuum coating. Possible surface treatments include, but are not limited to, applying a smoothing precoat to the surface or mechanical smoothing by, for example, calendering.

[0064] Surface treatment may include, for example, applying a precoat or primer layer to the substrate film. The precoat layer preferably functions to flatten irregularities and fill pores and pinholes present in the fibrous or porous substrate film. Surface treatment may also include subjecting the substrate surface to corona treatment or plasma treatment to improve adhesion.

[0065] Calendering may include hard nip or soft nip calendering in one or more passes or nips. Mechanical smoothing can also be combined with a precoating step performed before or after calendering.

[0066] Thus, in some embodiments, the metallized film layer further includes a precoat layer disposed between the substrate film and the vacuum coating layer.

[0067] In some embodiments, the precoat layer comprises a water-soluble polymer selected from the group consisting of polyvinyl alcohol, modified polyvinyl alcohol, polysaccharides and modified polysaccharides, or combinations thereof, preferably polyvinyl alcohol.

[0068] The PVOH may be a single type of PVOH or, for example, a mixture of two or more types of PVOH having different degrees of hydrolysis or viscosities. The PVOH may have a degree of hydrolysis in the range of, for example, 80 to 99 mol%, preferably 85 to 99 mol%. Examples of useful products include, for example, Kuraray Poval 4-98, Poval 6-98, Poval 10-98, Poval 15-99, Poval 20-98, Poval 30-98, or Poval 56-98, or mixtures thereof. As grades with a low degree of hydrolysis, Poval 4-88, Poval 6-88, Poval 8-88, Poval 18-88, Poval 22-88, or for example Poval 49-88 are preferred.

[0069] The modified polysaccharide can be, for example, a modified cellulose such as carboxymethyl cellulose (CMC) or hydroxypropyl cellulose (HPC), or a modified starch such as hydroxyalkylated starch, cyanoethylated starch, cationic or anionic starch, or starch ether or starch ester. Some preferred modified starches include hydroxypropylated starch, hydroxyethylated starch, dialdehyde starch, and carboxymethylated starch.

[0070] In some embodiments, the primer coat layer contains, based on dry weight, up to 50 wt%, preferably in the range of 1 to 20 wt% of microfibrillated cellulose (MFC) or nanocrystalline cellulose (NCC).

[0071] In some embodiments, the primer coat layer contains, based on dry weight, up to 20 wt%, preferably in the range of 1 to 15 wt% of platelet-shaped phyllosilicate, graphene, or graphene oxide, or a mixture thereof.

[0072] In some embodiments, the basis weight of the primer coat layer is in the range of 0.1 to 12 g / m 2 preferably in the range of 0.5 to 8 g / m 2 more preferably in the range of 1 to 6 g / m 2 of the film.

[0073] To minimize the risk of pinholes occurring in the primer coat layer, the primer coat layer can preferably be applied in at least two different coating steps while drying the coated film between each step.

[0074] The precoat layer can be applied by contact coating or non-contact coating methods. In the application to the MFC layer, non-contact coating methods are typically preferred to minimize the risk of substrate damage during coating. Examples of useful coating methods include, but are not limited to, rod coating, curtain coating, film press coating, cast coating, transfer coating, size press coating, flexographic coating, gate roll coating, twin roll HSM coating, blade coating (e.g., short-time blade coating), jet applicator coating, spray coating, gravure coating, or reverse gravure coating. In some embodiments, the coating is applied in a foamed form. Foamed coatings are advantageous because they can form films with higher solids content and lower water content compared to unfoamed coatings. The low water content of the foamed coating also reduces the problem of rewetting of the paperboard-based layer.

[0075] The vacuum coating layer is formed on the substrate film. Vacuum coating refers to a series of processes typically used to deposit layers of metals, metal oxides, and other inorganic and organic compositions atom-by-atom or molecule-by-molecule onto a solid surface. Multiple layers of the same or different materials can be combined. The processes can be further specified based on the vapor source, using a liquid source or a solid source in physical vapor deposition (PVD) and chemical vapor in chemical vapor deposition (CVD).

[0076] The vacuum coating layer can be formed on one or both sides of the substrate film.

[0077] Vacuum coating typically results in a very thin coating. In some embodiments, the vacuum coating layer has a thickness in the range of 10 to 600 nm, preferably in the range of 10 to 250 nm, more preferably in the range of 50 to 250 nm. This should be compared with the conventional aluminum foil used in the laminated body for packaging (this foil typically has a thickness in the range of about 3 to 12 μm).

[0078] The vacuum coating layer may be inorganic or organic. In some embodiments, the vacuum coating layer includes an inorganic vacuum coating layer such as a metal, metal oxide, or ceramic vacuum coating layer. Vacuum coatings of metals and metal oxides are often referred to as metallization.

[0079] In some embodiments, the vacuum coating layer includes a metal or metal oxide selected from the group consisting of aluminum, magnesium, silicon, copper, aluminum oxide, magnesium oxide, silicon oxide, and combinations thereof, preferably aluminum or aluminum oxide.

[0080] One preferred type of vacuum coating that is often used for its barrier properties, particularly its water vapor barrier properties, is a physical vapor deposition (PVD) coating of aluminum metal. Such a coating consists essentially of aluminum metal and can typically have a thickness from 50 to 250 nm, although thicknesses thinner than 50 nm can also be useful and may be preferred in some embodiments. The typical thickness of the vacuum coating layer corresponds to less than 1% of the aluminum metal material normally present in a conventional thickness for packaging, i.e., a 6.3 μm aluminum foil. Thus, in some embodiments, the vacuum coating layer includes aluminum.

[0081] The thickness of the vacuum coating layer can also be characterized by the optical density of the layer. In some embodiments, the vacuum coating layer has an optical density greater than 1.8, preferably greater than 2.0, greater than 2.5, greater than 2.7, or greater than 3.0.

[0082] The aluminum oxide vacuum coating layer, also known as an AlOx coating, can provide similar barrier properties as an aluminum metal coating, but also has the additional advantage that a thin AlOx coating is transparent to visible light.

[0083] In some embodiments, the vacuum coating layer includes an organic vacuum coating layer. The organic vacuum coating can be, for example, a vacuum coating carbon layer such as a diamond-like carbon (DLC) layer formed from carbon or an organic compound.

[0084] In some embodiments, the vacuum coating layer is applied to the substrate film by a transfer coating process. When the coating includes a metal, the transfer coating is generally also referred to as transfer metallization and generally involves using an adhesive layer applied between the vacuum coating layer and the substrate film to be coated to transfer a thin vacuum coating layer from the transfer coating substrate to the substrate film to be coated.

[0085] The transfer coating substrate includes a vacuum coating layer and a backing layer, and the vacuum coating layer and the backing layer are separated by a release layer having low adhesion to the vacuum coating layer and / or the backing layer such that the vacuum coating layer can be easily separated from the backing layer.

[0086] In the transfer coating process, an adhesive layer is applied onto the substrate film, or onto the vacuum coating layer, or onto both layers. The vacuum coating layer is transferred onto the substrate film using the adhesive layer applied onto the substrate film and / or the vacuum coating layer. The vacuum coating layer contacts and adheres to the substrate film using the adhesive layer applied onto the substrate film and / or the vacuum coating layer. Once the vacuum coating layer has adhered to the substrate film, the backing layer is removed from the vacuum coating layer, leaving the adhered vacuum coating layer and optionally the release layer on the substrate film. Any additional possible layers added between the release layer and the vacuum coating layer and / or on top of the vacuum coating layer will also remain on the substrate film.

[0087] The vacuum-coated film layer may further include a protective layer applied on top of the vacuum coating layer to protect the thin and sensitive vacuum coating layer during manufacture, handling, and transportation prior to the lamination process.

[0088] An adhesive composition is applied to the paperboard-based layer and / or the vacuum-coated film layer, and the paperboard-based layer is laminated to the vacuum-coated film layer using the adhesive composition in a press nip such that the adhesive composition forms an adhesive bonding layer between the paperboard-based layer and the vacuum-coated film layer. The adhesive composition may be applied directly to the paperboard-based layer surface, or first to the vacuum-coated film layer and then together with the vacuum-coated film layer to the paperboard-based layer, or both. The advantage of applying the adhesive composition to both surfaces is that surface wetting can be reduced.

[0089] The adhesive composition can be any composition that provides adhesion between the laminated layers. Typically, the adhesive composition includes an adhesive polymer. The adhesive composition can also include two or more adhesive polymers. The adhesive composition may consist of only one or more adhesive polymers, or may further include other additives to facilitate the coating process or to improve the properties of the adhesive bond layer. In some embodiments, the adhesive composition includes at least 50 wt% of an adhesive polymer, or a mixture of adhesive polymers, based on the dry weight.

[0090] The adhesive composition can be applied to the paperboard-based layer and / or the vacuum-coated film layer, for example, by extrusion coating or by liquid coating in the form of a dispersion, latex, or solution of the adhesive polymer in an aqueous carrier.

[0091] In some embodiments, the adhesive composition is applied by extrusion coating. Extrusion coating of thermoplastic polymers is useful because it can conveniently form a very thin and homogeneous adhesive film. In some embodiments, the adhesive composition includes one or more adhesive polymers selected from the group consisting of polyolefins, polyurethanes, and acrylic copolymers. In some embodiments, the adhesive composition includes a polyolefin, preferably polyethylene (PE).

[0092] The basis weight of the extrusion-coated adhesive bond layer can be in the range of 3 - 20 g / m 2 based on the dry weight.

[0093] The adhesive composition is preferably applied in the form of a solution or dispersion, which is spread into a thin and uniform layer on the substrate during application, i.e., and then dried, by a liquid film coating process. The liquid phase of the solution or dispersion is preferably water or an aqueous solution, but an organic solvent, or a mixture of water or an aqueous solution and an organic solvent can also be used. One or more adhesive polymers can be present in the form of being dissolved in the solution or dispersion, or in the form of polymer particles such as latex. The adhesive composition can be applied by a contact coating or non-contact coating method. Examples of useful coating methods include, but are not limited to, rod coating, curtain coating, film press coating, cast coating, transfer coating, size press coating, flexographic coating, gate roll coating, twin roll HSM coating, blade coating (e.g., short time blade coating), jet applicator coating, spray coating, gravure coating, or reverse gravure coating.

[0094] In some embodiments, the adhesive composition is applied in the form of a dispersion, latex, or solution of an adhesive polymer in an aqueous carrier.

[0095] In some embodiments, the dispersion, latex, or solution comprises polyvinyl alcohol (PVOH), styrene-acrylate (SA) latex, styrene-butadiene (SB) latex, starch, carboxymethyl cellulose (CMC), or polyolefin.

[0096] The basis weight of the adhesive bond layer applied in the form of a dispersion, latex, or solution can be in the range of 0.5 to 8 g / m 2 based on the dry weight. In some embodiments, the dispersion, latex, or solution is based on the dry weight in a single application step, in the range of 0.5 to 8 g / m 2It is applied as a single layer with a basis weight within the range. To minimize the risk of pinholes occurring in the adhesive bonding layer, the adhesive composition can preferably be applied in at least two different coating steps while drying the coated adhesive film between steps. In some embodiments, the dispersion, latex, or solution is applied in two or more consecutive application steps, such as 2+2 g / m 2 or 1+3 g / m 2 or 2+4 g / m 2 . By applying in two or more consecutive application steps, the first adhesive layer functions as the first coating and seals the surface, thereby reducing the penetration of the adhesive into the paperboard base layer.

[0097] In some embodiments, the adhesive composition contains at least 50% by weight of a water-soluble polymer or a water-soluble polymer mixture based on the dry weight. The water-soluble polymer of the adhesive composition dissolves in cold water within a given time or in hot water at a temperature, for example, below 100 °C or above 100 °C. In addition to functioning as an adhesive for the laminate, the water-soluble polymer also promotes the separation of the laminated layers during repulping. In some embodiments, the water-soluble polymer is selected from the group consisting of polyvinyl alcohol (PVOH), carboxymethyl cellulose (CMC), starch, alginate, and hemicellulose, preferably PVOH.

[0098] In some embodiments, the dispersion, latex, or solution has a solids content in the range of 10 to 70% by weight, preferably in the range of 15 to 65% by weight, at the time of its application. If the solids content is at least 10% by weight, more preferably at least 15% by weight, at the time of application, the adhesive can be fixed quickly and a good concentration of the adhesive composition on the surface can be obtained. If the solids content is low, there is too much water, which may cause the substrate to swell and problems may occur in dimensional stability and curing.

[0099] In some embodiments, the dispersion, latex, or solution has a viscosity in the range of 100 to 4000 mPas, preferably in the range of 300 to 2500 mPas, as determined using a Brookfield viscometer, such as a Brookfield DVNext rheometer, at a rotational speed of 100 rpm. This viscosity ensures good operability when using the rod coating method or the gravure coating method.

[0100] In some embodiments, the dispersion, latex, or solution has an AAGWR water retention value (Obo Academy water retention value) in the range of less than 250 g / m 2 , preferably in the range of 30 to 150 g / m 2 , as determined in accordance with TAPPI standard T701 pm-01. This water retention ensures good operability when using the rod coating method or the gravure coating method, minimizes the penetration of the coating composition into the base layer, and enables good dispersion of the adhesive on the surface of the base layer.

[0101] In some embodiments, at least one adhesive composition is applied in a foamed form. Foam coating is advantageous because it can form a film with a higher solids content and a lower water content compared to non-foam coating. Since the water content of the foam coating is low, the problem of rewetting of the paperboard base layer is also reduced. The foam can be formed using a polymeric or non-polymeric foaming agent. Examples of polymeric foaming agents include PVOH, hydrophobically modified starch, and hydrophobically modified ethyl hydroxyethyl cellulose.

[0102] In some embodiments, the adhesive composition further comprises a crosslinking agent capable of crosslinking the water-soluble polymer. Crosslinking improves the water vapor barrier properties of the adhesive layer. Suitable crosslinking agents include, but are not limited to, polyfunctional organic acids or aldehydes such as citric acid, glyoxal, zirconium carbonates, and glutaraldehyde. In some embodiments, the crosslinking agent is an organic acid, more preferably citric acid. The concentration of the crosslinking agent can be, for example, 1 to 20% by weight, preferably 1 to 15% by weight, based on the dry weight of the adhesive layer.

[0103] In some embodiments, the adhesive composition comprises PVOH and citric acid. Crosslinking PVOH with citric acid improves the water vapor barrier properties of the adhesive bonding layer.

[0104] In some embodiments, the adhesive composition further comprises, based on the dry weight, up to 50% by weight of microfibrillated cellulose (MFC), nanocrystalline cellulose, chemically modified cellulose derivatives such as sodium carboxymethyl cellulose, hydroxypropyl cellulose, ethylhydroxyethyl cellulose, cellulose acetate, hydroxyethyl cellulose, hemicellulose, or combinations thereof.

[0105] In some embodiments, the adhesive bonding layer also functions as a barrier coating layer. In some embodiments, the composition of the adhesive bonding layer can be selected as described above with reference to the barrier coating layer.

[0106] The surface of the paperboard base layer is laminated onto the surface of the vacuum-coated film layer using the adhesive composition in a press nip such that the adhesive composition forms an adhesive bonding layer between the paperboard base layer and the vacuum-coated film layer to form a laminate.

[0107] The press nip is formed by a press roll configured to apply pressure to the moving laminate. The press roll can typically be made of steel, or optionally of steel coated or surface-treated. The radius of the press roll is preferably at least 10 cm. In some embodiments, the radius of the press roll is at least 20 cm, at least 30 cm, or at least 40 cm. In some embodiments, a press nip is formed between the press roll and a counter roll or belt. The counter roll can be made of steel, optionally of steel coated or surface-treated, or can be made of a polymeric material such as plastic or rubber. The counter belt can be made of steel, optionally of steel coated or surface-treated, or can be made of a polymeric material such as plastic or rubber. A paperboard-based layer and a vacuum-coated film layer, and an adhesive composition disposed therebetween are supplied to the press nip and are subjected to pressure between the press roll and the counter roll or belt. In some embodiments, guide rolls are further provided before and / or after the press nip. The guide rolls can be used to guide the paperboard-based layer, the vacuum-coated film layer, and / or the formed laminate along a desired path. The guide rolls can also be used to adjust the angle between the paperboard-based layer and the vacuum-coated film when they are fed into the press nip.

[0108] In a conventional roll press nip, the nip is short and is formed between a press roll and a counter roll. Therefore, the press load of the nip typically cannot be increased beyond a certain limit without crushing or damaging the paperboard base layer. Also, in modern papermaking machines, the machine speed is high, so the residence time is impaired. Thus, in some embodiments, the press nip is an extended nip, i.e., a nip in which the contact point between the press roll and the laminate is extended in the machine direction. Thereby, the time for which the laminate is under pressure within the nip is extended, and the press load and / or temperature required to achieve the same laminating effect as a shorter nip can be reduced. In some embodiments, the extended nip is a shoe nip. In some embodiments, the extended nip or shoe nip has a nip contact length in the range of at least 10 mm, preferably at least 50 mm, more preferably at least 100 mm, for example from 100 mm to 1000 mm.

[0109] In some embodiments, the press nip has a press load in the range of 0.5 to 150 kN / m, preferably in the range of 1 to 100 kN / m, more preferably in the range of 2 to 75 kN / m, or in the range of 3 to 50 kN / m. The press load is large enough to achieve sufficient contact between the paperboard base layer, the vacuum-coated film layer, and the adhesive composition disposed therebetween, but not so large as to crush and damage the paperboard base layer. In a preferred embodiment, at least 80% of the average thickness of the paperboard base layer is retained after the press nip. Preferably, at least 85%, more preferably at least 90%, even more preferably at least 93% of the average thickness of the paperboard base layer is retained after the press nip. The press load also enables the adhesive composition to solidify more uniformly between the paperboard base layer and the vacuum-coated film layer rather than being pressed against the paperboard base layer.

[0110] The press roll and / or counter roll or belt may be heated to heat the laminate within the nip. Heating the laminate can improve the contact between the paperboard base layer, the vacuum-coated film layer, and the adhesive composition disposed therebetween, and can also promote drying and / or curing of the adhesive composition. In some embodiments, the press roll and / or counter roll or belt is heated to a temperature in the range of 40 to 250 °C, preferably in the range of 70 to 250 °C.

[0111] When an adhesive composition is applied to the paperboard base layer during the lamination process, not only the paperboard base layer but also the completed laminate may curl. As the paperboard reel is consumed and the diameter of the reel decreases, the inherent curl of the paperboard base layer supplied to the lamination step will increase, so the curl of the base layer and the laminate may also deteriorate as the process progresses.

[0112] The inventors have discovered that the curl of the completed laminate can be advantageously reduced by adjusting the position of the press nip in a direction perpendicular to the lamination plane during lamination.

[0113] Accordingly, in some embodiments of the method of the present invention, the position of the press nip is adjustable in a direction perpendicular to the lamination plane during lamination to correct for changes in the curl of the formed laminate.

[0114] In some embodiments of the method of the present invention, the position of the press nip is adjusted in a direction perpendicular to the lamination plane during lamination to correct for changes in the curl of the formed laminate.

[0115] In some embodiments of the method of the present invention, the curl is reduced by adjusting the press nip in a direction perpendicular to the lamination plane and towards the paperboard base layer side of the laminate. Adjusting the press nip towards the paperboard base layer side of the laminate will cause a bend or curve in the path of the web, where the paperboard base layer will be on the outside and the vacuum-coated film layer will be on the inside of the bend or curve.

[0116] In some embodiments of the method of the present invention, the curl is reduced by adjusting the press nip in a direction perpendicular to the lamination plane and towards the side of the vacuum-coated film layer of the laminate. Adjusting the press nip in the direction towards the side of the vacuum-coated film layer of the laminate creates a bend or curve in the path of the web, where the vacuum-coated film layer will be on the outside and the paperboard base layer will be on the inside of the bend or curve.

[0117] The inventors have further discovered that in order to avoid cracking of the vacuum coating of the vacuum-coated film layer, the angle between the paperboard base layer and the vacuum-coated film when they are fed into the press nip is important. As the paperboard reel is consumed and the diameter of the reel decreases, the inherent curl of the paperboard base layer supplied to the lamination step will increase, so the angle between the paperboard base layer and the vacuum-coated film can increase as the lamination process progresses.

[0118] In some embodiments, the position of the press nip is adjustable in the machine direction during lamination to correct for changes in the angle between the paperboard base layer and the vacuum-coated film at the press nip. Thus, in some embodiments, the position of the press nip is adjustable in both a direction perpendicular to the lamination plane and the machine direction during the lamination process.

[0119] In some embodiments, the position of the press nip is adjusted in the machine direction during lamination to correct for changes in the angle between the paperboard base layer and the vacuum-coated film at the press nip. Thus, in some embodiments, the position of the press nip is adjusted in both a direction perpendicular to the lamination plane and the machine direction during the lamination process.

[0120] In some embodiments, the angle between the paperboard base layer and the vacuum-coated film in the press nip is maintained at less than 50°, preferably less than 45°.

[0121] In some embodiments, the position of the press roll and / or the counter roll or belt is adjustable independently of the other. In some embodiments, one of the press roll and the counter roll or belt is adjustable in a direction perpendicular to the lamination plane and in the machine direction. In some embodiments, the press roll and / or the counter roll or belt are adjustable in both a direction perpendicular to the lamination plane and in the machine direction. In some embodiments, one of the press roll and the counter roll or belt is adjustable in a direction perpendicular to the lamination plane, and the other of the press roll and the counter roll or belt is adjustable in the machine direction. In some embodiments, one of the press roll and the counter roll or belt is adjustable in a direction perpendicular to the lamination plane and in the machine direction, and the other of the press roll and the counter roll or belt is adjustable only in a direction perpendicular to the lamination plane or only in the machine direction. In embodiments where the position of the press roll and / or the counter roll or belt is adjustable independently of the other, the press nip can be tilted. In embodiments where the counter roll or belt is a belt or shoe, the belt or shoe can be tilted, and the press roll can be adjusted accordingly.

[0122] In some embodiments, the position of the press roll and / or the counter roll or belt is adjusted independently of the other. In some embodiments, one of the press roll and the counter roll or belt is adjusted in a direction perpendicular to the lamination plane and in the machine direction. In some embodiments, the press roll and / or the counter roll or belt are adjusted in both a direction perpendicular to the lamination plane and in the machine direction. In some embodiments, one of the press roll and the counter roll or belt is adjusted in a direction perpendicular to the lamination plane, and the other of the press roll and the counter roll or belt is adjusted in the machine direction. In some embodiments, one of the press roll and the counter roll or belt is adjusted in a direction perpendicular to the lamination plane and in the machine direction, and the other of the press roll and the counter roll or belt is adjusted only in a direction perpendicular to the lamination plane or only in the machine direction. In embodiments where the position of the press roll and / or the counter roll or belt is adjusted independently of the other, the press nip can be tilted. In embodiments where the counter roll or belt is a belt or shoe, the belt or shoe can be tilted, and the press roll can be adjusted accordingly.

[0123] In some embodiments, the press nip is tilted. This means that the position of the press roll and / or the counter roll is adjusted relative to the other such that the tangent plane is tilted at the contact point between the rolls. By tilting the press nip during lamination, changes in the curl of the formed laminate can be corrected. Tilting the press nip can increase the contact time between the paperboard base layer, the vacuum-coated film layer, and / or the formed laminate and the press roll or counter roll, respectively. This can be useful, for example, in increasing the contact time between the laminate and the heated press roll.

[0124] The inventors have further discovered that it is important to avoid sharp turns in the web path during the lamination process in order to avoid cracking of the vacuum coating of the vacuum-coated film layer. The vacuum-coated film layer is laminated to a thick paperboard having a basis weight of at least 100 g / m 2 and a density of less than 800 kg / m 3 It is particularly important to avoid sharp turns in the web path after lamination. This is because when subjected to sharp turns, the stress applied to the vacuum coating of such a laminate may increase. Thus, in some embodiments, the paperboard base layer, the vacuum-coated film, and the resulting laminate are not subjected to a radius of curvature of less than 10 cm, preferably less than 20 cm, less than 30 cm, or less than 40 cm. In some embodiments, the resulting laminate is not subjected to a radius of curvature of less than 10 cm, preferably less than 20 cm, less than 30 cm, or less than 40 cm.

[0125] The paperboard-based packaging laminate may further be provided with a polymer seal layer on one or both sides. The polymer seal layer provides a heat-sealing function on the surface of the paperboard-based packaging laminate and can further provide improved liquid barrier properties and mechanical protection. The polymer seal layer can be applied, for example, by extrusion coating, film lamination, or dispersion coating.

[0126] In some embodiments, the method further comprises e) applying at least one polymer seal layer to at least one side of the laminate including.

[0127] In some embodiments, the method comprises e) applying at least one polymer seal layer to both sides of the laminate including.

[0128] The polymer seal layer can generally include any of the thermoplastic polymers commonly used in the heat-sealable layers of paperboard-based packaging laminates, or polymers specifically used in paper for liquid or food packaging. Examples include polyethylene (PE), polypropylene (PP), polyhydroxyalkanoate (PHA), polylactic acid (PLA), polyglycolic acid (PGA), polybutylene terephthalate (PBT), starch, and cellulose. In some embodiments, the polymer seal layer includes a polyolefin layer, preferably a polyethylene layer. Polyethylene, especially low-density polyethylene (LDPE) and high-density polyethylene (HDPE), are the most common and versatile polymers used in paper for liquid or food packaging. The polymer used is preferably manufactured from renewable materials.

[0129] In some embodiments, the polymer seal layer is formed by extrusion coating a polymer onto the surface of the paperboard-based layer or the resulting laminate. Extrusion coating is a process of applying a molten plastic material to a substrate to form a very thin, smooth, and uniform layer. The coating can be formed from the extruded plastic itself, or a solid plastic film can be laminated onto the substrate using the molten plastic as an adhesive.

[0130] The basis weight of each of the polymer seal layers is preferably less than 50 g / m 2 . To achieve a continuous and substantially defect-free film, the basis weight of the polymer seal layer is typically at least 8 g / m 2 , preferably at least 12 g / m 2 . In some embodiments, the basis weight of the polymer seal layer ranges from 8 to 50 g / m 2 , preferably from 12 to 50 g / m 2 .

[0131] In a more specific embodiment, the paperboard-based packaging laminate includes a paperboard-based layer, PVOH as an adhesive composition, and metallized greaseproof paper as a vacuum-coated film layer, and optionally, a polyethylene layer as a polymer seal layer disposed on one or both sides of the laminate.

[0132] In some embodiments, the resulting paperboard-based packaging laminate has an oxygen transmission rate (OTR) of less than 30 cc / m 2 / 24 h, preferably less than 20 cc / m 2 / 24 h, more preferably less than 10 cc / m 2 / 24 h, most preferably less than 5 cc / m 2 / 24 h, measured in accordance with ASTM standard F1927-20 at 50% relative humidity and 23 °C.

[0133] The resulting paperboard-based packaging laminate has significantly improved resistance to water vapor. In some embodiments, the resulting paperboard-based packaging laminate has a water vapor transmission rate (WVTR) of less than 30 g / m 2 / 24 h, preferably less than 20 g / m 2 / 24 h, more preferably less than 10 g / m 2 / 24 h, most preferably less than 5 g / m 2 / 24 h, measured in accordance with ASTM standard F1249-20 at 50% relative humidity and 23 °C. Thereby, the packaging laminate of the present invention becomes an interesting and practicable alternative to conventional materials using an aluminum foil layer.

[0134] In addition, the paperboard-based packaging laminate of the present invention can provide an alternative to conventional materials using an aluminum foil layer and can be more easily repulped and recycled. The adhesive bonding layer of the paperboard-based packaging laminate of the present invention preferably contains at least 50% by weight of a water-soluble polymer based on the dry weight. It has been found that the water-soluble polymer disposed in contact between the paperboard-based layer and the vacuum-coated film layer can effectively separate the vacuum-coated layer from the paperboard-based layer during repulping. In some embodiments, the paperboard-based packaging laminate has a defect rate of less than 30%, preferably less than 20%, more preferably less than 10% in accordance with PTS RH 021 / 97.

[0135] According to a second aspect presented herein, a method of manufacturing a container, particularly a container for liquid or food packaging, comprising: a) manufacturing a paperboard-based packaging laminate as described with reference to the first aspect, and b) converting the paperboard-based packaging laminate into a container is provided.

[0136] In some embodiments, the vacuum-coated layer faces the inside of the container.

Brief Description of the Drawings

[0137]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0138] Referring to FIG. 1, a paperboard base layer is provided from a paperboard reel (1). At a first coating station (2), a dispersion coating is applied to a first surface of the paperboard base layer. At a second coating station (3), an aqueous adhesive composition containing polyvinyl alcohol (PVOH) is applied to the barrier coating. A vacuum-coated film layer is provided from a vacuum-coated film reel (4). The vacuum-coated film layer is laminated to the adhesive-coated surface of the paperboard base layer at a press nip (5) formed between a press roll (6) and a counter roll (7). The position of the press nip is gradually adjusted in a direction (8) perpendicular to the lamination plane and towards the paperboard base layer side of the laminate during the lamination process. Adjusting the press nip towards the paperboard base layer side of the laminate causes a bend or curve in the web path where the paperboard base layer will be on the outside and the vacuum-coated film layer will be on the inside of the bend or curve. Optionally, the position of the press nip is also gradually adjusted in the machine direction (9) during lamination to correct for an increase in the angle (α) between the paperboard base layer and the vacuum-coated film at the press nip. Then, a polymer seal layer is provided on both sides of the laminate by extruding polyethylene in an extrusion station (10). Guide rolls (11, 12) guide the paperboard base layer and the formed laminate along a desired path. Guide roll (11) can also be used to adjust the angle between them when the paperboard base layer and the vacuum-coated film are fed to the press nip. The adjustment of the press nip can be controlled online by measuring appropriate parameters of the paperboard base layer, the vacuum-coated film layer, and / or the formed laminate, such as moisture content or curl, and automatically, preferably using a CPU and an appropriate algorithm, adjusting the press nip to correct for changes in the measured parameters.

[0139] FIG. 2 shows the process described with reference to FIG. 1, but with the position of the press nip (5) adjusted in a direction perpendicular to the lamination plane.

[0140] Figure 3 shows the process described with reference to Figure 1, but the position of the press nip (5) is adjusted in the machine direction.

[0141] Figure 4 shows the process described with reference to Figure 1, but the position of the press nip (5) is adjusted in a direction perpendicular to the lamination plane and the press nip is inclined. This means that the position of the press roll and / or the counter roll is adjusted relative to the other so that the tangent plane is inclined at the contact point between the rolls.

[0142] Generally, products, polymers, materials, layers, and processes are described in terms of "comprising" various components or steps, but products, polymers, materials, layers, and processes can also be said to "consist essentially of" or "consist of" various components and steps.

[0143] The present invention has been described with reference to various exemplary embodiments, but it will be understood by those skilled in the art that various changes can be made without departing from the scope of the present invention and that elements of the present invention can be replaced with equivalents. Furthermore, many changes can be made to adapt a particular situation or material to the teachings of the present invention without departing from the essential scope of the present invention. Accordingly, the present invention is not intended to be limited to the particular embodiments disclosed as the best mode contemplated for carrying out the present invention, but is intended to include all embodiments within the scope of the appended claims.

Claims

1. A method for manufacturing a paperboard-based laminate for packaging, a) To provide a paperboard base layer, b) To provide a vacuum-coated film layer, c) Applying the adhesive composition to the paperboard base layer and / or the vacuum-coated film layer. d) Laminating the surface of the paperboard base layer to the surface of the vacuum-coated film layer using the adhesive composition in a pressnip, such that the adhesive composition forms an adhesive bonding layer between the paperboard base layer and the vacuum-coated film layer to form a laminate. Includes, The position of the press nip is adjusted in a direction perpendicular to the lamination surface during lamination to correct changes in the curl of the formed laminate. method.

2. The method according to claim 1, wherein the position of the press nip is adjusted in the machine direction during lamination to compensate for changes in the angle between the paperboard base layer and the vacuum-coated film at the press nip.

3. The method according to claim 1, wherein the angle between the paperboard base layer and the vacuum-coated film in the pressnip is maintained at less than 50°, preferably less than 45°.

4. The method according to claim 1, wherein the press nip is formed between the press roll and the counter roll or belt.

5. The method according to claim 1, wherein the press nip is an expansion nip, preferably a shoe nip.

6. The method according to claim 1, wherein the press nip has a press load in the range of 0.5 to 150 kN / m, preferably in the range of 1 to 100 kN / m, more preferably in the range of 2 to 75 kN / m or 3 to 50 kN / m.

7. The method according to claim 4, wherein the press roll and / or the counter roll or belt are heated to a temperature in the range of 40 to 250°C, preferably in the range of 70 to 250°C.

8. The aforementioned paperboard base layer is 100 to 1000 g / m² ２ The method according to claim 1, having a basis weight within the range of [specified range].

9. The aforementioned paperboard base layer has a density of 800 kg / m². ３ Less than 600 kg / m ３ The method according to claim 1, having a density less than [amount missing].

10. The method according to claim 1, wherein the cardboard base layer has a bending resistance of more than 80 mN, preferably more than 100 mN, in the mechanical direction, as measured in accordance with ISO 2493 (L&W, 15°).

11. The method according to claim 1, wherein the cardboard base layer has a bending resistance of more than 40 mN, preferably more than 45 mN, in the machine transverse direction, as measured in accordance with ISO 2493 (L&W, 15°).

12. The method according to claim 1, wherein the cardboard base layer is multiply cardboard.

13. The method according to claim 1, wherein the cardboard base layer includes foamed molded cardboard.

14. The method according to claim 1, wherein the vacuum-coated film layer includes a vacuum-coated layer formed on a substrate film.

15. The method according to claim 14, wherein the base film is a plastic film, preferably a film formed from polyethylene (PE), polypropylene (PP), or polyhydroxyalkanoate (PHA).

16. The method according to claim 14, wherein the base film is a fiber-based film, preferably a cellulose-based film, and more preferably a film formed from microfibrillated cellulose (MFC).

17. The method according to claim 14, wherein the vacuum coating layer includes an inorganic vacuum coating layer such as a metal, metal oxide, or ceramic vacuum coating layer, preferably an aluminum or aluminum oxide vacuum coating layer.

18. The method according to claim 14, wherein the vacuum coating layer includes an organic vacuum coating layer.

19. The method according to claim 14, wherein the vacuum coating layer has a thickness in the range of 10 to 600 nm, preferably in the range of 10 to 250 nm.

20. The method according to claim 1, wherein the adhesive composition comprises an adhesive polymer.

21. The method according to claim 1, wherein the adhesive composition is applied by extrusion coating.

22. The method according to claim 21, wherein the adhesive composition comprises a polyolefin, preferably polyethylene (PE).

23. The method according to claim 1, wherein the adhesive composition is applied in the form of a dispersion of adhesive polymer in an aqueous carrier, a latex, or a solution.

24. The method according to claim 23, wherein the dispersion, latex, or solution comprises polyvinyl alcohol (PVOH), styrene-acrylate (SA) latex, styrene-butadiene (SB) latex, starch, carboxymethylcellulose (CMC), or polyolefin.

25. The method according to claim 23, wherein the dispersion, latex, or solution has a solid content in the range of 10 to 70% by weight, preferably 15 to 65% by weight, at the time of application.

26. e) Applying at least one polymer seal layer to at least one side of the laminate. The method according to claim 1, further comprising:

27. e) Applying at least one polymer seal layer to both sides of the laminate. The method according to claim 1, including the method described in claim 1.

28. The method according to claim 26, wherein the polymer seal layer comprises a polyolefin layer, preferably a polyethylene layer.

29. The resulting cardboard-based packaging laminate was measured at 50% relative humidity and 23°C in accordance with ASTM standard F1927-20, yielding 30 cc / m³. ２ Less than 24 hours, preferably 20 cc / m³ ２ Less than 24 hours, more preferably 10 cc / m³ ２ Less than 24 hours, most preferably 5 cc / m³ ２ The method according to claim 1, having an oxygen permeability (OTR) of less than 24 hours.

30. The obtained paperboard-based packaging laminate has a water vapor transmission rate (WVTR) of less than 30 g / m ２ / 24 h, preferably less than 20 g / m ２ / 24 h, more preferably less than 10 g / m ２ / 24 h, most preferably less than 5 g / m ２ / 24 h, according to the method of claim 1, measured in accordance with ASTM standard F1249-20 at a relative humidity of 50% and 23°C.

31. A method for manufacturing containers, particularly containers for liquids or food packaging, a) To manufacture a paperboard-based packaging laminate as described in claim 1, and b) Converting the cardboard-based packaging laminate into a container. Methods that include...

32. The method according to claim 31, wherein the vacuum coating layer faces the inside of the container.

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