Paper or paperboard based packaging laminates

Abstract

The present invention relates to a paper or paperboard based packaging laminate comprising a paper or paperboard base layer, an inorganic coating layer, a PVOH coating layer, and a metallized film layer, wherein the inorganic coating layer is disposed between and in contact with the base layer and the PVOH coating layer, and the metallized film layer is laminated to the PVOH coating layer, and the packaging laminate has a viscosity of less than 5 cc / m2 measured according to standard ASTM F-1927 at 90% relative humidity and 38°C. 2 The present invention relates to a paper or paperboard based packaging laminate having an Oxygen Transfer Rate (OTR) of less than 1 / day.The present invention further relates to a container comprising the paper or paperboard based packaging laminate.

Description

[Technical Field]

[0001] This disclosure relates to paper and paperboard-based packaging materials, and more particularly to paper and paperboard-based packaging laminates that have low and consistent oxygen transmission rates (OTR) at high relative humidity (RH). [Background technology]

[0002] In order to combine the mechanical properties of paperboard with the barrier and sealing properties of plastic films, paper and paperboard are often coated with plastics.Paperboard with a uniform, relatively small amount of suitable plastic material can provide the properties required to make paperboard suitable for many demanding applications, such as liquid packaging board.In liquid packaging board, polyolefin coatings are often used as liquid barrier layers, heat sealing layers, and adhesives.However, because it is difficult to separate the polymer from the fibers, recycling of such polymer-coated cardboard is difficult.

[0003] In addition, in many cases, unless the coating layer is thick or a combination of various polymer coating layers is used, the gas barrier properties of polymer-coated paperboard are still insufficient. Therefore, in order to ensure high gas barrier properties, light barrier properties, and high rigidity, polymer-coated paperboard is often provided with one or more layers of aluminum foil. However, the addition of polymer and aluminum layers adds considerable costs and makes the material more difficult to recycle. Also, due to its high carbon footprint, there is a desire to replace aluminum foil in paper and paperboard-based packaging materials.

[0004] Aseptic packaging for long-term storage products, such as milk and juice, is typically made from liquid packaging board (LPB), which includes a multi-layer paperboard base substrate, an outermost heat-sealable polyolefin (e.g., polyethylene, PE) layer, and an innermost layer of polyolefin and aluminum. The aluminum layer, which is required to provide oxygen barrier properties, is typically incorporated between layers of polyethylene, resulting in the following structure: PE / paperboard / PE / aluminum / PE.

[0005] Attempts have been made in the prior art to replace aluminum foil with more environmentally friendly and / or more recyclable solutions, but to date have not been really successful.

[0006] More recently, microfibrillated cellulose (MFC) membranes and coatings have been developed in which defibrillated cellulose fibrils are dispersed, for example, in water, and then reorganized and recombined together to form dense membranes with excellent gas barrier properties. Unfortunately, the gas barrier properties of such MFC membranes tend to deteriorate at high humidity.

[0007] Therefore, there remains a need for improved solutions to replace plastic films and aluminum foil in paper and paperboard based packaging materials while maintaining acceptable liquid and oxygen barrier properties. At the same time, there is a need to replace plastic films and aluminum foil with alternatives that facilitate the repulping and recycling of the used packaging materials. Summary of the Invention

[0008] It is an object of the present disclosure to provide an alternative to plastic films and aluminum foils that are commonly used as barrier films to provide oxygen barrier properties in packaging materials, such as liquid packaging paperboard.

[0009] It is a further object of the present disclosure to provide a paper or paperboard based packaging laminate, such as a liquid packaging paperboard, that provides good oxygen barrier properties even at higher relative humidities and higher temperatures.

[0010] A further object of the present disclosure is to provide a method for determining the viscosity of a liquid at 90% relative humidity and 38°C, with a viscosity of 5 cc / m 2 measured in accordance with standard ASTM F-1927. 2 The present invention provides a paper or paperboard based packaging laminate having an oxygen transfer rate (OTR) of less than 1 / day.

[0011] It is a further object of the present disclosure to provide a paper or paperboard based packaging laminate, such as a liquid packaging paperboard, that includes an oxygen barrier layer that facilitates repulping of the paperboard compared to packaging laminates that use traditional plastic films and aluminum foil.

[0012] It is a further object of the present disclosure to provide a paper or paperboard based packaging laminate having a reject rate of less than 30%, preferably less than 20%, in accordance with PTS RH021 / 97.

[0013] The above objectives, as well as other objectives that will be recognized by those skilled in the art in light of this disclosure, are achieved by various aspects of the present disclosure.

[0014] According to a first aspect described herein, a paper or paperboard substrate; an inorganic coating layer; a PVOH coating layer, and metallized film layer 1. A paper or paperboard based packaging laminate comprising: an inorganic coating layer disposed between and in contact with the base layer and the PVOH coating layer; A metallized membrane layer is laminated to the PVOH coating layer; Packaging laminates have a permeability of 5 cc / m2 measured in accordance with standard ASTM F-1927 at 90% relative humidity and 38°C. 2A paper or paperboard based packaging laminate is provided having an oxygen transfer rate (OTR) of less than 1 / day.

[0015] Paper generally refers to a material produced in thin sheets from wood pulp or other fibrous substances, including cellulose fibers, used for writing, drawing, or printing, or as a packaging material.

[0016] Paperboard generally refers to strong, thick paper or cardboard containing cellulose fibers used for boxes and other types of packaging. Paperboard may be bleached or unbleached, coated or uncoated, and produced in a variety of thicknesses, depending on the end-use requirements.

[0017] A paper or paperboard-based packaging laminate is a packaging material formed primarily or entirely from paper or paperboard. It can be made from pulp, including pulp from untreated fibers, such as mechanical pulp, chemical pulp, and / or thermomechanical pulp. It can also be made from broke or recycled paper. In addition to paper or paperboard, a paper or paperboard-based packaging laminate can contain additional layers or coatings designed to improve the performance and / or appearance of the packaging laminate.

[0018] Paper or paperboard-based packaging laminates typically have a first outermost surface to serve as the exterior or print surface, and a second outermost surface to serve as the interior surface of the package. The base side of the paper or paperboard, including the metallized film layer, is intended to serve as the interior surface of the package.

[0019] The packaging laminate layers of the present invention can provide excellent oxygen barrier properties, water vapor barrier properties, and liquid barrier properties. Particularly useful is the combination of high oxygen barrier properties and high water vapor barrier properties at high humidity and high temperature, made possible by the combination of the PVOH layer and the metallized film layer. The term high humidity, in the context of this disclosure, generally refers to a relative humidity (RH) greater than 80%. The term high temperature, in the context of this disclosure, generally refers to a temperature greater than 23°C. More specifically, the term high temperature, in the context of this disclosure, can refer to a temperature in the range of 25-50°C. The oxygen barrier properties and water vapor barrier properties of packaging laminates at high humidity and high temperature are typically measured at a representative relative humidity (RH) of 90% and a temperature of 38°C.

[0020] The packaging laminate of the present invention has a moisture content of 5 cc / m 2 measured according to standard ASTM F-1927 at 90% relative humidity and 38°C. 2 / day, which makes the packaging laminate of the present invention an interesting and viable alternative to traditional materials that use aluminum foil layers.

[0021] Furthermore, the paper or paperboard-based packaging laminate of the present invention can provide an alternative to conventional materials using aluminum foil layers, and they can be more easily repulped and recycled. The paper or paperboard-based packaging laminate of the present invention includes an inorganic coating layer disposed between the substrate and the PVOH coating layer, and in contact with the substrate and the PVOH coating layer. It has been found that the combination of the inorganic coating layer and the PVOH coating layer of the present invention can effectively decompose the metallized film layer from the substrate during repulping. In addition, the inorganic coating layer can inhibit undesired migration of PVOH into the substrate and protect the PVOH coating against water vapor. In some embodiments, the paper or paperboard-based packaging laminate has a reject rate of less than 30%, preferably less than 20%, and more preferably less than 10% according to PTS RH021 / 97.

[0022] In some embodiments, the inorganic coating layer comprises, based on the total dry weight of the inorganic coating layer: 50-95 wt% particulate inorganic matter, and Binder 5-50wt% Includes.

[0023] In some embodiments, the inorganic coating layer comprises 10-35 wt % of a binder.

[0024] In some embodiments, the inorganic coating layer comprises, based on the total dry weight of the inorganic coating layer: 10 to 35 wt %, preferably 10 to 20 wt %, of a binder; and Particulate inorganic matter: 90 to 65 wt%, preferably 90 to 80 wt% Includes.

[0025] The high amount of particulate inorganic matter in the inorganic coating layer facilitates the removal of the metallized membrane layer from the substrate during repulping.

[0026] In some embodiments, the particulate mineral is selected from the group consisting of kaolin, calcium carbonate, bentonite, talc, and combinations thereof, preferably kaolin or calcium carbonate, more preferably kaolin.

[0027] In some embodiments, the particulate inorganic material comprises 80-100 wt % calcium carbonate and 0-20 wt % clay, calculated on a dry weight basis of the total particulate inorganic material in the inorganic coating layer. The use of a high amount of calcium carbonate with a low shape factor in the inorganic coating layer allows for a higher solids content and a lower amount of binder in the coating layer while still achieving good coverage. The low amount of binder also facilitates removal of the metallized film layer. Preferably, the shape factor of the calcium carbonate is less than 10, preferably between 0.1 and 10, or between 0.1 and 5. As used herein, "shape factor" is a measure of the average weight ratio of the average particle diameter to the particle thickness, which can be measured using electrical conductivity methods. Furthermore, calcium carbonate is less reactive than clay, which more readily dissolves calcium carbonate in an acid environment, thereby further facilitating recycling.

[0028] The calcium carbonate used is preferably 20m 2 / g, more preferably less than 15m 2 / g or less, e.g., 3 to 20 m 2 / g or 3-15m 2 / g. Compared to clays, pigments with such low surface areas are easier to recycle, especially since they require less chemicals. As used herein, "surface area" is measured by adsorption using the BET isotherm (ISO 9277:2010).

[0029] In one embodiment, the calcium carbonate contained in the particulate inorganic material is a mixture of a first calcium carbonate containing 50 to 70 weight percent particles having a particle size of less than 2 μm and a second calcium carbonate containing 80 to 100 weight percent particles having a particulate size of less than 2 μm. The particle sizes can be measured using a Mastersizer 2000. Preferably, the first calcium carbonate has a median particle size (d50) by weight between 1 and 2 μm, and the second calcium carbonate has a median particle size (d50) by weight between 0.5 and 0.9 μm. In a preferred embodiment, the inorganic coating layer contains 20 to 40 wt %, preferably 20 to 30 wt %, of the first calcium carbonate and 80 to 60 wt %, preferably 80 to 70 wt %, of the second calcium carbonate, calculated based on the total dry weight of calcium carbonate in the inorganic coating layer.

[0030] In an embodiment, the particulate inorganic material comprises 80-90 wt % calcium carbonate and 10-20 wt % clay, calculated on the dry weight of the total particulate inorganic material in the inorganic coating layer, and this particulate inorganic material mixture is optimized to provide both high barrier properties and excellent recyclability.

[0031] The binder may be a water-dispersible or water-soluble binder. In some embodiments, the water-dispersible binder is a latex binder. In some embodiments, the water-soluble binder is starch, PVOH, a cellulose derivative such as CMC, protein, or seaweed. The advantage of using a water-soluble binder is that the laminate is even more easily recycled.

[0032] In some embodiments, the basis weight of the inorganic coating layer is 4 to 25 g / m 2 More preferably, it is in the range of 6 to 20 g / m 2 The range is.

[0033] The inorganic coating layer is preferably applied in at least two different coating steps, with drying of the coating between steps.

[0034] The inorganic coating layer preferably has a PPS (Parker Printsurf) smoothness according to ISO 8791-4 of less than 5 μm. The inorganic coating layer preferably has a Cobb-Unger value (30 seconds, bs) of 20 g / m 2 less than 1 to 20 g / m 2 in the range of 5 to 15 g / m 2 The Cobb-Unger value is a measure of oil absorption and is determined by the SCAN-P37:77 (30 seconds) method.

[0035] The packaging laminate of the present invention includes a polyvinyl alcohol (PVOH) coating layer. The PVOH coating layer is disposed between the inorganic coating layer and the metallized film layer. In some embodiments, the PVOH coating layer is in direct contact with the inorganic coating layer. The PVOH coating layer can be applied to the inorganic coating layer before the metallized film layer is laminated to the PVOH coating layer.

[0036] The PVOH in the PVOH coating layer is soluble in cold water for a predetermined period of time or after heating to a temperature of less than 100°C. The water solubility of the PVOH coating layer improves separation of the metallized membrane layer from the base layer during repulping. The PVOH can have a degree of hydrolysis ranging from 80 to 99 mol%, preferably from 85 to 98 mol%. The crystallinity of the PVOH, as measured by wide-angle x-ray scattering, is preferably less than 0.6, preferably less than 0.5, and more preferably less than 0.4.

[0037] In some embodiments, the PVOH coating layer comprises at least 50 wt% PVOH, preferably at least 70 wt% PVOH, based on the total dry weight of the PVOH coating layer.

[0038] The PVOH may be unmodified PVOH or modified PVOH. The modified PVOH may preferably be ethylene-modified PVOH.

[0039] The PVOH may be a single type of PVOH, or may comprise a mixture of two or more types of PVOH, for example, with different degrees of hydrolysis or viscosities. The PVOH may have a degree of hydrolysis ranging from 80 to 99 mol%, preferably from 85 to 99 mol%. Furthermore, the PVOH preferably has a viscosity of greater than 5 mPa × sec in a 4% aqueous solution according to DIN 53015 / JIS K6726 at 20°C (without additives and without pH change, i.e., obtained by dispersing and dissolving in distilled water, for example). Examples of useful products include Kuraray Poval 4-98, Poval 6-98, Poval 10-98, Poval 20-98, Poval 30-98, or Poval 56-98, or mixtures thereof. Partially hydrolyzed grades such as Poval 4-88, Poval 6-88, Poval 8-88, Poval 18-88, Poval 22-88, or Poval 49-88 are preferred. Alternatively, fully hydrolyzed grades (98-99.9%) of PVOH can also be used. The PVOH preferably has an ash content of less than 0.9 wt%, preferably less than 0.7 wt%, less than 0.4 wt%, or less than 0.2 wt%.

[0040] To minimize the risk of pinholes in the PVOH coating layer, the PVOH coating layer is preferably applied in at least two different coating steps, with the coating film being dried between steps. In some embodiments, the PVOH coating layer is multi-layered, with at least one layer containing low-molecular-weight PVOH. This will further facilitate subsequent removal of the metallized film layer from the base layer of paper or paperboard during repulping.

[0041] The PVOH coating layer is preferably formed in the form of an aqueous solution or dispersion by a liquid thin-film coating method, i.e., by spreading it on the substrate to form a thin, uniform layer, and then drying. The PVOH coating layer can be applied by a contact 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-dwell time blade coating), jet applicator coating, spray coating, gravure coating, or reverse gravure coating.

[0042] In some embodiments, at least one PVOH coating layer is applied in the form of a foam. Foamed coatings are advantageous because they allow for the formation of thin films with higher solids and lower water content than non-foamed coatings. The lower water content of foamed coatings also reduces the problem of rewetting the substrate. 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 ethylhydroxyethyl cellulose.

[0043] The basis weight of the PVOH coating layer is generally between 1 and 20 g / m 2 In some embodiments, the basis weight of the PVOH coating layer can range from 2 to 15 g / m 2 in the range of 3 to 12 g / m 2 The range is.

[0044] In some embodiments, a cross-linking agent is added to the inorganic coating layer and / or the PVOH coating layer. The cross-linking agent can improve water resistance and adhesion at the inorganic coating-PVOH coating interface. Suitable cross-linking agents include, but are not limited to, glyoxal, citric acid, and glutaraldehyde. The concentration of the cross-linking agent can be, for example, 1 to 20 wt %, preferably 1 to 15 wt %, based on the weight of the inorganic layer or PVOH. To increase cross-linking at the interface between the inorganic coating layer and the PVOH coating layer, a cross-linking agent solution can be applied on top of the inorganic coating layer before forming the PVOH coating layer.

[0045] The paper or paperboard based packaging laminate of the present invention comprises a metallized film layer laminated to the PVOH coating layer, which preferably further improves the oxygen and / or water vapor barrier properties of the laminate.

[0046] The metallized film layer includes a substrate film and a metallized layer applied to at least one surface of the substrate film.

[0047] The metallized film layer preferably comprises a metallized polymer film or a metallized cellulose-based film. The combination of the metallized polymer film and the PVOH coating layer further improves the barrier properties of the laminate and protects both the PVOH coating layer and the metallized layer from cracking during laminate conversion. The metallized cellulose-based film can also improve the barrier properties of the laminate, making the laminate more recyclable.

[0048] The substrate film of the present invention may be any substrate film suitable for the continuous application of a substantially continuous vacuum coating layer thereon, having a thickness in the range of 1 to 500 nm. The substrate film preferably comprises a material in the form of a thin film or sheet, having a smooth, dense, and relatively low porosity surface onto which the vacuum coating can be applied. The substrate film preferably has almost no pinholes or should have no pinholes. The amount of pinholes in a thin film or sheet-form substrate film can be determined, for example, in accordance with standard EN13676:2001. The substrate film preferably has a pinhole density of 10 pinholes / m or less. 2 Less than 8 pinholes / m 2 Less than 2 pinholes / m 2 Includes less than 1m 2 The amount of pinholes per 100 ml can be measured, for example, by optical inspection, for example, according to standard EN 13676:2001. The substrate membrane preferably has a Gurley-Hill porosity of more than 30,000 sec / 100 ml, preferably more than 40,000 sec / 100 ml, measured according to standard ISO 5636 / 5. The OTR of the substrate membrane, determined at 23°C and 50% RH, is >5 cc / m 2 / day, e.g., >10cc / m 2 / day, or >20cc / m 2 / day. The thickness of the substrate film is typically in the range of 10 to 100 μm, preferably in the range of 15 to 80 μm, and more preferably in the range of 20 to 60 μm. The density of the substrate film is typically >850 kg / m 3 or >900 kg / m 3 or >950 kg / m 3 or >1000 kg / m 3 , preferably 1050 to 1250 kg / m 3 The range is.

[0049] The substrate membrane can be composed of a single layer of material or a multilayer structure composed of two or more layers of the same or different materials. The substrate membrane can include or consist of, for example, a polymeric membrane formed from a synthetic or bio-based polymer. Alternatively, the substrate membrane can include or consist of a dense sheet of a fiber-based material. The substrate membrane can also include or consist of a combination of a fiber-based material and a synthetic or bio-based polymer, for example, in the form of a laminate or polymer-coated paper or composite. In some embodiments, the substrate membrane includes or consists of a mixture of fibers and polymers. In some embodiments, the substrate membrane includes one layer of a fiber-based material and one layer of a polymer. For example, the substrate membrane can be composed of a fiber-based layer, e.g., a microfibrillated cellulose (MFC) membrane coated with a polymeric layer, e.g., a polyvinyl alcohol (PVOH) coating, to improve smoothness and reduce porosity of the MFC membrane surface.

[0050] In some embodiments, the substrate film is a polymer film. The polymer of the polymer film may be selected from the group consisting of, for example, polyolefins such as polyethylene or polypropylene, PET, polyimides, fluoropolymers, and polyesters such as PEEK.

[0051] In a preferred embodiment, the polymer of the polymer film is a biaxially oriented polypropylene (BOPP) film. BOPP film is preferred for use in food packaging applications, for example, due to its high moisture resistance, optical clarity, and high tensile strength. Preferably, the BOPP film contains at least 50% recycled PP or PP based on renewable resources.

[0052] Improved solutions are needed to replace barrier layers, aluminum foil and polyolefin films, in packaging laminates, such as liquid packaging board, with alternatives that facilitate repulping and recycling of used packaging laminates.

[0053] The substrate film is preferably bio-based, more preferably cellulose-based. Bio-based or cellulose-based means that more than 50% by weight of the substrate film is of natural, or preferably cellulose, origin. The use of cellulose-based substrate films is particularly useful as barrier films for use in paper or paperboard laminates, as the laminate can be recycled as a single material.

[0054] The metallized membrane layer can advantageously be produced almost entirely from bio-based materials, preferably cellulose-based materials, thereby facilitating the repulping and recycling of used paper and paperboard-based packaging laminates. Such packaging materials containing 95% or more by weight of cellulose material, with the remaining 5% being other materials that do not affect the recycling of the packaging material, are sometimes referred to as monomaterials. Thus, in some embodiments, more than 95% by weight of the metallized membrane layer is cellulose-based.

[0055] In some embodiments, the base film comprises a high density paper, such as a superfinished or half-glazed paper, formed from chemical or mechanical pulp or a mixture thereof.

[0056] In some embodiments, the substrate membrane comprises a high density paper, e.g., a superfinished paper, formed from chemical or mechanical pulp or a mixture thereof, and is subsequently coated or laminated with an MFC membrane or layer to provide a surface suitable for the successive application of a substantially continuous vacuum coating layer thereon, having a thickness in the range of 1 to 500 nm.

[0057] In some embodiments, the substrate membrane comprises a regenerated cellulose membrane, for example, cellophane.

[0058] Microfibrillated cellulose (MFC) has been identified as an interesting component for use in the barrier film of paper and paperboard packaging materials.In some embodiments, the substrate film is composed of or includes an MFC film.In other words, the substrate can be completely made of an MFC film, or can include an MFC film as one of multiple layers.

[0059] Microfibrillated cellulose (MFC) in the context of the present application is intended to mean cellulose particles, fibres or fibrils having a width or diameter between 20 nm and 1000 nm.

[0060] There are various methods for producing MFC, such as single or multiple beating, prehydrolysis, followed by beating or high-shear fibrillation or liberation of fibrils. To make MFC production energy-efficient and sustainable, one or more pretreatment steps are usually required. Thus, the cellulose fibers of the pulp used in producing MFC can be intact or can be enzymatically or chemically pretreated, for example, to reduce the amount of hemicellulose or lignin. Cellulose fibers can also be chemically modified before fibrillation, so that the cellulose molecules contain other (or more) functional groups than those found in the original cellulose. These groups include, among others, carboxymethyl (CM) groups, aldehyde groups, and / or carboxyl groups (cellulose obtained by N-oxyl-mediated oxidation, e.g., "TEMPO"), or quaternary ammonium (cationic cellulose). After being modified or oxidized in one of the aforementioned methods, the fibers are easily defibrated by MFC.

[0061] MFCs can be made from wood-based cellulose fibers, both hardwood and softwood. They can also be made from microbial sources, agricultural fibers such as straw pulp, bamboo, bagasse, or other non-wood fiber sources. They can also be made from pulp from virgin fibers, including mechanical, chemical, and / or thermomechanical pulps. They can also be made from broke or recycled paper.

[0062] Fibrous or porous substrate membranes, such as MFC membranes, can preferably be combined with a surface treatment to improve smoothness, reduce the porosity of the substrate surface, and make the surface more suitable for metallization. Possible surface treatments include, but are not limited to, providing the surface with a smoothing precoat or mechanical smoothing, for example by calendering.

[0063] Surface treatment can include, for example, applying a precoat or primer layer to the fibrous or porous substrate layer. The precoat layer preferably acts to smooth out irregularities and fill pores and pinholes present in the fibrous or porous substrate film. Surface treatment can also include corona or plasma treatment of the substrate surface to improve adhesion.

[0064] Calendering can include hard-nip or soft-nip calendering in one or more steps or nips. Mechanical smoothing can also be combined with a pre-coat treatment step performed before or after calendering.

[0065] Thus, in some embodiments, the metallized film layer further comprises a precoat layer disposed between the substrate film and the vacuum coating layer.

[0066] 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.

[0067] The PVOH may be a single type of PVOH, or may comprise a mixture of two or more types of PVOH, differing, for example, in degree of hydrolysis or viscosity. The PVOH may have a degree of hydrolysis ranging, for example, from 80 to 99 mol%, preferably from 85 to 99 mol%. Furthermore, the PVOH preferably has a viscosity of greater than 5 mPa × sec in a 4% aqueous solution according to DIN 53015 / JIS K6726 at 20°C (without additives and without pH change, i.e., obtained when dispersed and dissolved in distilled water, for example). Examples of useful products include Kuraray Poval 4-98, Poval 6-98, Poval 10-98, Poval 20-98, Poval 30-98, or Poval 56-98, or mixtures thereof. From the partially hydrolyzed grades, Poval 4-88, Poval 6-88, Poval 8-88, Poval 18-88, Poval 22-88 or, for example, Poval 49-88 are preferred.

[0068] The modified polysaccharide may 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 a starch ether or starch ester. Some preferred modified starches include hydroxypropylated starch, hydroxyethylated starch, dialdehyde starch, and carboxymethylated starch.

[0069] In some embodiments, the basis weight of the precoat layer is from 0.1 to 12 g / m 2 range, preferably 0.5 to 8 g / m 2 range, more preferably 1 to 6 g / m 2 The range is.

[0070] To minimize the risk of pinholes in the precoat layer, the precoat layer is preferably applied in at least two different coating steps, with the coating drying between steps.

[0071] The precoat layer can be applied by contact or non-contact coating methods. For application to the MFC layer, non-contact coating methods are typically preferred to minimize the risk of damage to the substrate during coating. Examples of useful coating methods include, but are not limited to, rod coating, curtain coating, film pressure coating, cast coating, transfer coating, size press coating, flexographic printing coating, gate roll coating, twin-roll HSM coating, blade coating (e.g., short-dwell time blade coating), jet applicator coating, spray coating, gravure coating, or reverse gravure coating. In some embodiments, the coating is applied in the form of a foam. Foam coatings are advantageous because they allow for the formation of thin films with higher solids and lower water content compared to non-foam coatings. The lower water content of foam coatings also reduces rewetting issues in the MFC layer.

[0072] Metallization refers to a class of methods used to vapor-deposit layers of metals or metal oxides onto solid surfaces atom by atom or molecule by molecule. Multiple layers of the same or different materials may be combined. Methods may be further specified based on the vapor source; physical vapor deposition (PVD) uses liquid or solid sources, while chemical vapor deposition (CVD) uses chemical vapor.

[0073] In some embodiments, the metallization layer is formed by vapor deposition of a metal or metal oxide on the substrate film, preferably by physical vapor deposition (PVD) or chemical vapor deposition (CVD).

[0074] In some embodiments, only one surface of the substrate membrane is metallized, hi some embodiments, both surfaces of the substrate membrane are metallized.

[0075] In some embodiments, the metallization layer comprises a metal, metal oxide, or ceramic oxide selected from the group consisting of aluminum, magnesium, silicon, copper, aluminum oxide, magnesium oxide, silicon dioxide, and combinations thereof, preferably aluminum oxide. Aluminum oxide vacuum coatings, also known as AlOx coatings, can provide similar barrier properties to aluminum metal coatings, but have the added advantage that thin AlOx coatings are transparent to visible light.

[0076] The metallized layer of the present invention can have a thickness in the range of 1 to 500 nm. In some embodiments, the metallized layer has a thickness in the range of 1 to 100 nm, preferably in the range of 10 to 100 nm, and more preferably in the range of 20 to 50 nm. In some embodiments, the metallized layer has a thickness in the range of 50 to 250 mg / m 2 in the range of 75 to 150 mg / m 2 The base weight ranges from 1000 to 10 ...

[0077] One preferred type of metallized coating, often used for its barrier properties, particularly water vapor barrier properties, is a physical vapor deposition (PVD) coating of aluminum metal. Such coatings, consisting essentially of aluminum metal, can typically have a thickness of 10-50 nm. The thickness of the metallized layer represents less than 1% of the aluminum metal material typically present in conventional thickness, i.e., 6.3 μm, aluminum foil for packaging.

[0078] The basis weight of the metallized membrane layer will depend on the substrate membrane used. The basis weight of the metallized membrane layer is typically between 1 and 100 g / m 2 In some embodiments, the basis weight of the metallized membrane layer is in the range of 10 to 70 g / m 2 in the range of 10 to 70 g / m 2 For metallized polymeric films, the basis weight is typically at the lower end of the range, e.g., 10 to 30 g / m 2whereas for metallized cellulose-based membranes, the basis weight may be higher, e.g., 20 to 100 g / m 2 The range may be:

[0079] The metallized film layer is laminated to the PVOH coating layer. The metallized film layer may be laminated to the PVOH layer using any suitable means of adhesion.

[0080] In some embodiments, the metallized membrane layer is laminated to the PVOH coating layer using the PVOH of the PVOH layer as the adhesive.

[0081] In some embodiments, the metallized membrane layer is attached to the PVOH coating layer by an adhesive tie layer disposed between the PVOH coating layer and the metallized membrane layer. The adhesive tie layer can comprise any suitable adhesive for providing or improving lamination adhesion between the PVOH coating layer and the metallized membrane layer. The tie layer can be, for example, an extruded polyolefin adhesive, preferably polyethylene, or a dispersion adhesive, preferably a latex or polyolefin dispersion. In some embodiments, the tie layer can comprise ethylene vinyl acetate (EVA) or a polymeric acrylate, such as ethylene butyl acrylate. The coating weight of the adhesive tie layer is typically 0.5 to 15 g / m. 2 in the range of 1 to 12 g / m 2 may be in the range of

[0082] In some embodiments, the adhesive bonding layer comprises polyethylene or ethylene modified PVOH.

[0083] In some embodiments, the paper or paperboard base layer has a density of 20 to 500 g / m 2 range, preferably 80 to 400 g / m 2 The base weight ranges from 1000 to 10 ...

[0084] In some embodiments, the paper or paperboard substrate is a multi-ply paperboard.

[0085] The construction of the paper or paperboard-based packaging laminate of the present invention allows for the use of higher amounts of recycled fibers in the paper or paperboard base layer because the barrier structure prevents migration of mineral oil-based compounds. Thus, in some embodiments, the paper or paperboard base layer comprises at least 5 wt% recycled fibers, preferably at least 10 wt% recycled fibers.

[0086] Paper or paperboard based packaging laminates may further comprise an outermost protective polymeric layer on one or both sides.

[0087] In some embodiments, the paper or paperboard based packaging laminate further comprises a first protective polymeric layer, preferably a polyethylene layer, disposed on the paper or paperboard base layer.

[0088] In some embodiments, the paper or paperboard based packaging laminate further comprises a second protective polymer layer, preferably a polyethylene layer, disposed on the metallized film layer.

[0089] A protective polymer layer may, of course, interfere with repulpability, but may still be required or desired in some applications. Additional polymer layers may be applied, for example, by extrusion coating, thin film lamination, or dispersion coating.

[0090] The protective polymer layer can generally comprise any of the thermoplastic polymers commonly used in paper or paperboard-based packaging laminates, or in particular, polymers used in liquid packaging boards. Examples include polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), polyhydroxyalkanoate (PHA), polylactic acid (PLA), polyglycolic acid (PGA), starch, and cellulose. Polyethylene, particularly low-density polyethylene (LDPE) and high-density polyethylene (HDPE), is the most common and versatile polymer used in liquid packaging boards.

[0091] Thermoplastic polymers are useful because they can be conveniently processed by extrusion coating techniques to form extremely thin, uniform films with good liquid barrier properties. In some embodiments, the additional polymer layer comprises polypropylene or polyethylene. In a preferred embodiment, the protective polymer layer comprises polyethylene, more preferably LDPE or HDPE.

[0092] In some embodiments, the protective polymer layer is formed by extrusion coating of a polymer onto the surface of the barrier film. Extrusion coating is a method in which molten plastic material is applied to a substrate to form an extremely thin, smooth, and uniform layer. The coating can be formed by extruding plastic itself, or molten plastic can be used as an adhesive to laminate a solid plastic film onto the substrate. Common plastic resins used in extrusion coating include polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET).

[0093] The basis weight of each of the protective polymer layers is preferably 50 g / m 2 To achieve a continuous, substantially defect-free thin film, typically at least 8 g / m 2 , preferably at least 12 g / m 2 In some embodiments, the basis weight of the protective polymer layer is from 8 to 50 g / m 2 range, preferably 12 to 50 g / m 2 The range is.

[0094] It has been found that the combination of a metallized film layer and a polyvinyl alcohol (PVOH) layer results in paper and paperboard packaging laminates with excellent gas and water vapor barrier properties.

[0095] In some embodiments, the paper or paperboard based packaging laminate has a moisture content of 5 cc / m 2 measured according to standard ASTM F-1927 at 50% relative humidity and 23°C. 2 / day, preferably less than 3cc / m 2 / day, preferably less than 2cc / m 2 have an oxygen transfer rate (OTR) of less than 1 / day.

[0096] In some embodiments, the paper or paperboard based packaging laminate has a moisture content of 3 cc / m 2 measured according to standard ASTM F-1927 at 90% relative humidity and 38°C. 2 / day, preferably less than 2cc / m 2 have an oxygen transfer rate (OTR) of less than 100 / day.

[0097] In some embodiments, the paper or paperboard based packaging laminate has a surface area of ​​5 g / m 2 measured according to standard ASTM F1249 at 50% relative humidity and 23°C. 2 / day, preferably less than 0.5 g / m 2 / day water vapor mobility rate (WVTR) of less than

[0098] In some embodiments, the paper or paperboard based packaging laminate has a surface area of ​​5 g / m 2 measured according to standard ASTM F1249 at 90% relative humidity and 38°C. 2 / day, preferably less than 1 g / m 2 / day water vapor mobility rate (WVTR) of less than

[0099] Improved solutions are needed to replace the barrier layers of aluminum foil and polyolefin films in packaging laminates, such as liquid packaging board, with alternatives that facilitate repulping and recycling of used packaging laminates. The combination of an inorganic coating layer and a PVOH coating layer according to the present disclosure has been found to facilitate repulping and recycling of used packaging laminates.

[0100] In some embodiments, the paper or paperboard based packaging laminate has a reject rate according to PTS RH021 / 97 of less than 30%, preferably less than 20%, more preferably less than 10%.

[0101] According to a second aspect described herein, there is provided a container, in particular a liquid packaging container, comprising a paper or paperboard based packaging laminate according to the first aspect.

[0102] In some embodiments, the metallized membrane layer faces the inside of the container.

[0103] Generally, products, polymers, materials, layers, and methods are described in terms of "comprising" various components or various steps, but the products, polymers, materials, layers, and methods may also "consist essentially of" or "consist of" the various components and various steps.

[0104] While the present invention has been described in terms of various exemplary embodiments, it will be understood by those skilled in the art that various modifications can be made and equivalents can be substituted for the elements of the present invention without departing from the scope of the invention. In addition, many modifications 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 invention. Therefore, it is not intended that the invention be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but rather that the invention will include all embodiments falling within the scope of the appended claims. [Example]

[0105] Four samples were prepared as follows: Base cardboard: Three-ply cardboard with a first surface layer of bleached sulfate pulp, a second surface layer of unbleached sulfate pulp, and a middle layer of unbleached sulfate pulp and unbleached CTMP, 195-281 g / m 2 Inorganic coating: The base cardboard was coated on the first surface layer with an inorganic coating according to Table 1 below, to a total coating weight of about 22 g / m 2 It was double coated (precoat + topcoat). TIFF2024525657000001.tif73170

[0106] The inorganic coated base cardboard was then coated with a PVOH dispersion coating layer at a coating weight of 5 g / m 2 It was covered up to.

[0107] 18μm metallized BOPP film (basis weight approx. 16g / m 2 ) was laminated onto the PVOH coating layer by extrusion lamination using LDPE as a tie layer.

[0108] Finally, a layer of LLDPE was extrusion coated onto the metallized BOPP.

[0109] The oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) were measured for the samples (see Table 2). As can be seen in Table 2, both the OTR and WVTR were extremely low, even at high temperatures and humidity. TIFF2024525657000002.tif40170

Claims

1. A base layer of paper or cardboard, An inorganic coating layer, A PVOH coating layer, and A metallized film layer A packaging laminate based on paper or cardboard, comprising: The inorganic coating layer is disposed between the base layer and the PVOH coating layer and in contact with the base layer and the PVOH coating layer, The metallized film layer is laminated on the PVOH coating layer, The packaging laminate has an oxygen transmission rate (OTR) of less than 5 cc / m ２ / day, measured in accordance with standard ASTM F-1927 at a relative humidity of 90% and 38°C, A packaging laminate based on paper or cardboard.

2. The inorganic coating layer is based on the total dry weight of the inorganic coating layer, 65-90 wt% of particulate inorganic matter, and 10-35 wt% of a binder The packaging laminate according to claim 1, comprising:

3. The particulate inorganic matter is selected from the group consisting of kaolin, calcium carbonate, bentonite, talc, and combinations thereof, preferably from kaolin or calcium carbonate, more preferably from kaolin. The packaging laminate according to claim 2, based on paper or cardboard.

4. The inorganic coating layer contains 80-100 wt% of calcium carbonate and 0-20 wt% of clay, calculated based on the dry weight of all the particulate inorganic matter in the inorganic coating layer. The packaging laminate according to claim 3, based on paper or cardboard.

5. The calcium carbonate contains a mixture of a first calcium carbonate containing 50-70 wt% of particles having a particle size of less than 2 μm and a second calcium carbonate containing 80-100 wt% of particles having a particle size of less than 2 μm. The packaging laminate according to claim 4, based on paper or cardboard. Claim 6 The packaging laminate based on paper or cardboard according to claim 2, wherein the binder is a latex binder. Claim 7 The packaging laminate based on paper or cardboard according to claim 1, wherein the basis weight of the inorganic coating layer is in the range of 4 to 25 g / m ２ , more preferably in the range of 6 to 20 g / m ２ . Claim 8 The packaging laminate based on paper or cardboard according to claim 1, wherein the PVOH coating layer contains at least 70 wt% of PVOH based on the total dry weight of the PVOH coating layer. Claim 9 The packaging laminate based on paper or cardboard according to claim 1, wherein the basis weight of the PVOH coating layer is in the range of 1 to 20 g / m ２ , preferably in the range of 2 to 15 g / m ２ , more preferably in the range of 3 to 12 g / m ２ . Claim 10 The packaging laminate based on paper or cardboard according to claim 1, wherein the metallized film layer comprises a metallized polymer film or a metallized cellulose-based film. Claim 11 The packaging laminate based on paper or cardboard according to claim 1, wherein more than 95% by weight of the metallized film layer is cellulose-based. Claim 12 The packaging laminate based on paper or cardboard according to claim 1, wherein the metallized film layer comprises a metallized layer formed by vapor deposition of a metal or metal oxide on a thin film layer, preferably by physical vapor deposition (PVD) or chemical vapor deposition (CVD). Claim 13 The packaging laminate based on the paper or cardboard according to claim 12, wherein the metallized layer is selected from the group consisting of aluminum, magnesium, silicon, copper, aluminum oxide, magnesium oxide, silicon oxide, and combinations thereof, and is a metal, metal oxide, or ceramic oxide, preferably containing aluminum oxide.

14. The packaging laminate based on the paper or cardboard according to claim 12, wherein the metallized layer has a layer thickness in the range of 1 to 100 nm, preferably in the range of 10 to 100 nm, more preferably in the range of 20 to 50 nm.

15. The grammage of the metallized film layer is in the range of 10 to 70 g / m ２ and more preferably in the range of 10 to 50 g / m ２ for the packaging laminate based on the paper or cardboard according to claim 1.

16. The packaging laminate based on the paper or cardboard according to claim 1, wherein the metallized film layer is adhered to the PVOH coating layer by an adhesive bonding layer.

17. The packaging laminate based on the paper or cardboard according to claim 16, wherein the adhesive bonding layer contains polyethylene or ethylene-modified PVOH.

18. The base layer of the paper or cardboard has a basis weight in the range of 20 to 500 g / m ２ and preferably in the range of 80 to 400 g / m ２ for the packaging laminate based on the paper or cardboard according to claim 1.

19. The packaging laminate based on the paper or cardboard according to claim 1, wherein the base layer of the paper or cardboard is a multi-ply cardboard.

20. The packaging laminate based on the paper or cardboard according to claim 1, wherein the base layer of the paper or cardboard contains at least 5 wt% recycled fibers, preferably at least 10 wt% recycled fibers.

21. The packaging laminate based on the paper or cardboard according to claim 1, further comprising a first protective polymer layer, preferably a polyethylene layer, disposed on a base layer of paper or cardboard.

22. The packaging laminate based on the paper or cardboard according to claim 1, further comprising a second protective polymer layer, preferably a polyethylene layer, disposed on a metallized film layer.

23. Having an oxygen transmission rate (OTR) of less than 5 cc / m ２ / day, preferably less than 3 cc / m ２ / day, more preferably less than 2 cc / m ２ / day, of the packaging laminate based on the paper or cardboard according to claim 1, measured in accordance with standard ASTM F-1927 at a relative humidity of 50% and 23 °C.

24. Having an oxygen transmission rate (OTR) of less than 3 cc / m ２ / day, preferably less than 2 cc / m ２ / day, of the packaging laminate based on the paper or cardboard according to claim 1, measured in accordance with standard ASTM F-1927 at a relative humidity of 90% and 38 °C.

25. Having a water vapor transmission rate (WVTR) of less than 5 g / m ２ / day, preferably less than 0.5 g / m ２ / day, of the packaging laminate based on the paper or cardboard according to claim 1, measured in accordance with standard ASTM F1249 at a relative humidity of 50% and 23 °C.

26. Having a water vapor transmission rate (WVTR) of less than 5 g / m ２ / day, preferably less than 1 g / m ２ / day, of the packaging laminate based on the paper or cardboard according to claim 1, measured in accordance with standard ASTM F1249 at a relative humidity of 90% and 38 °C.

27. Having a defect rate of less than 30%, preferably less than 20%, more preferably less than 10%, compliant with PTS RH021 / 97, of the packaging laminate based on the paper or cardboard according to claim 1. Claim 28 A container comprising a packaging laminate based on paper or cardboard according to claim 1. Claim 29 The container according to claim 28, wherein the metallized film layer faces the inside of the container.