Recyclable paper packaging material with high barrier properties against water vapor and oxygen.

Abstract

A recyclable, easily manufactured paper packaging laminate having high barrier properties against water vapor, oxygen and / or aromas, The barrier film (3) comprises at least one substrate layer (4), an adhesive layer (5) and a barrier layer (6), wherein the adhesive layer (5) is disposed between the substrate layer (4) and the barrier layer (6); the substrate layer (4) is mainly composed of polyethylene or polypropylene, with a polyethylene or polypropylene content of at least 60% by weight of the substrate layer (4); At least the at least one substrate layer (4) of the barrier film (4) is stretched; the proportion of the paper layer (2) is between 50% and 90% by weight of the paper packaging laminate (1), and The barrier film (3) is adhered to the paper layer (2) using a hydrophilic adhesive layer (9), provided that the paper layer (2) is not coated on the barrier film (3) side. A paper packaging laminate characterized by:

Description

[Technical Field]

[0001] This invention relates to a material with a load capacity of 30 to 360 g / m². 2 This invention relates to a recyclable paper packaging laminate comprising a paper layer using paper having a basis weight up to a certain amount, and a barrier film bonded to the paper layer, which has high oxygen, water vapor, and / or aroma barrier properties in addition to being recyclable. [Background technology]

[0002] In the packaging industry, paper-based packaging laminates with various properties are used depending on the application. These paper-based packaging laminates are typically laminated with multilayer plastic films produced by extrusion, co-extrusion (both flat film and blow film methods), or lamination (joining individual layers using lamination adhesives), or combinations thereof. Paper-based packaging laminates may also incorporate layers that are not made of plastic, such as aluminum or another type of paper. These paper-based packaging laminates usually also have an outer sealing layer for processing into desired packaging materials, such as bags, sacks, paper pouches, etc., by heat sealing.

[0003] One typical requirement for laminates used in paper packaging is a barrier function against water vapor, oxygen, and aromatic substances. For this purpose, laminates for paper packaging generally include a barrier layer made of aluminum or a suitable barrier polymer, such as ethylene-vinyl alcohol copolymer (EVOH) or polyamide (PA).

[0004] Similarly, paper packaging laminates typically include a sealing layer to allow them to be processed into packaging material by heat sealing. The sealing layer is typically made from polyolefins, usually polypropylene (PP) or polyethylene (PE) of various densities such as LLDPE, LDPE, MDPE, or HDPE (blends or multilayers using the same or different types are also included).

[0005] In addition, further layers may be included to impart desired properties such as toughness, rigidity, and tear resistance to the laminated material for paper packaging.

[0006] In order to easily process laminated paper packaging materials, these materials should not warp or curl during processing. Therefore, laminated plastic films typically use a symmetrical layer structure.

[0007] Furthermore, it is known that the properties of paper packaging laminates can be altered by the uniaxial or biaxial orientation of the plastic layer within the paper packaging laminate. Such orientation can be achieved by stretching the plastic film in the mechanical direction (longitudinal direction of the paper packaging laminate) and / or transverse direction (perpendicular to the longitudinal direction) during the extrusion process, for example, in a multiple bubble extrusion process, or only after the extrusion process. This orientation of the plastic film can improve, in particular, its stiffness, tensile strength, and toughness.

[0008] However, it should be noted that in blow film extrusion and flat film extrusion, the extrusion gap (1.5–2.5 mm for blow film) or the gap between the extrusion dies is significantly larger than the final thickness of the extruded film (typically 10–200 μm). Therefore, the extruded molten material is stretched at a temperature significantly higher than the melting point of the polymer being extruded, thereby achieving the final thickness. In blow film extrusion, the molten material is typically stretched, for example, by about 2–3 times in the transverse direction (the so-called blow-up ratio) and 1:10–1:100 times in the longitudinal direction (the so-called draw-off ratio). However, the stretching during extrusion cannot be compared to the stretching of plastic films. This is because stretching is usually performed at a temperature slightly below the melting point of the polymer (typically between 5°C and 20°C) in order to permanently align the disordered polymer and partially crystalline regions in the stretching direction. In so-called MDO stretching (stretching only in the machine direction), the material is typically processed with a stretching gap (roll spacing) of 40 to 100 mm. In biaxial stretching, the material is then stretched laterally in a heated oven.

[0009] Paper is often used as a packaging material, particularly for erocosity reasons, because it is highly recyclable. However, paper alone cannot be used as a packaging material to meet the usual requirements for packaging materials, such as barrier function against water vapor, oxygen, and / or fragrances, or sealing properties for manufacturing packaging materials, because paper alone does not possess significant barrier properties. Therefore, in the field of flexible packaging materials, paper is usually combined with other layers, such as layers made of plastic or metal, to meet barrier requirements. However, such paper packaging laminates, such as the commonly used paper / aluminum / polyethylene structures, are usually difficult or impossible to recycle due to the materials used.

[0010] Recently, paper packaging materials with only a thin barrier layer and sealing layer are increasingly being introduced to the market, ensuring that foreign components / impurities in paper recycling do not exceed 5% of the total weight of the packaging material, as permitted by EN643.1. See, for example, the CPI (Condederation of Paper Industry) "Design Tips for Recycling" at www.wrap.org.uk / packaging.

[0011] It should also be noted that some coating materials, such as silicones and waxes, as well as some colorants, are considered hazardous to the recycling process, even at concentrations of less than 5%.

[0012] WO2013 / 086950A1 (Patent Document 1) discloses a recyclable laminate using a "water-dispersible ionomer (WPI)" as an adhesive, which bonds a thermoplastic material to a base material made of paper or aluminum. The laminate is recyclable because the paper layer and the thermoplastic material can be separated via the WPI, however the recycling step requires a particularly high water temperature of 80°C and a particularly long processing time of 1 hour.

[0013] EP3194164B1 (Patent Document 2) describes a laminated structure for food use comprising paper as a material layer, aluminum as a gas barrier layer, and a polymer layer as a laminated material. In particular, it highlights improved environmental compatibility achieved by omitting ozone treatment during the surface treatment of the polymer. [Prior art documents] [Patent Documents]

[0014] [Patent Document 1] WO2013 / 086950A1 [Patent Document 2] EP3194164B1 [Overview of the project] [Problems that the invention aims to solve]

[0015] One of the objectives of the present invention is to provide a recyclable, paper-based laminate for packaging that is easy to manufacture, readily recyclable, and has high barrier properties against water vapor, oxygen, and / or fragrances. [Means for solving the problem]

[0016] The aforementioned problem is that the barrier film is • comprising at least one base layer, a bonding layer, and a barrier layer, wherein the bonding layer is disposed between the base layer and the barrier layer. The base layer is mainly composed of polyethylene or polypropylene, with a polyethylene or polypropylene ratio of at least 60% by weight, preferably at least 70% by weight, and very preferably at least 80% by weight of the base layer 4. • At least one of the substrate layers of the barrier film is stretched. The proportion of the paper layer is between 50% and 90% by weight of the laminated material for paper packaging, preferably between 70% and 90% by weight, and The barrier film is bonded to the paper layer using a hydrophilic adhesive layer; however, the paper layer is not coated on the side facing the barrier film. This is resolved by using a polyolefin (PE or PP) content of 10 to 50% by weight, particularly 10 to 30% by weight, i.e., a significantly higher polyolefin content than previously considered necessary, and a dominant paper content in the laminate for paper packaging, thereby achieving (high) barrier and recyclability functions. In this way, recyclable paper packaging materials that still have a high barrier effect against water vapor, oxygen, and / or fragrances can be produced.

[0017] The barrier film comprises a base material layer joined to a barrier layer via a joining layer and can be designed asymmetrically. The asymmetric barrier film can be designed to be thinner, thereby reducing the proportion of polymers in the laminate for paper packaging. In this case, the barrier layer is preferably arranged on the paper layer side and joined to the paper layer via an adhesive layer.

[0018] Alternatively, the barrier film is symmetrically designed with a barrier layer joined to the base material layer using joining layers on both sides. At this time, one of the base material layers is joined to the paper layer via an adhesive layer. The symmetric barrier film can be processed more easily because the symmetric film is relatively difficult to curl. Also, similarly, the barrier layer in the symmetric structure is well protected.

[0019] The barrier layer can be designed as a barrier coating in the form of a metal coating or a coating of silicon oxide or aluminum oxide, or as a layer made of a barrier polymer, preferably a polyamide or an ethylene-vinyl alcohol copolymer. Additionally, in order to further enhance the barrier effect, a barrier coating in the form of a metal coating or a coating of silicon oxide or aluminum oxide can also be provided on the layer made of a barrier polymer. This makes it possible to very well adapt the barrier effect to the individual barrier requirements of the laminate for paper packaging.

[0020] Preferably, the barrier film is stretched. This can be achieved, for example, by co-extruding the barrier film as a whole and then stretching it. Additionally, by stretching the barrier polymer, its barrier effect can also be enhanced.

[0021] For many packaging applications, a sealing layer is required, which can be bonded to a barrier film on the opposite side of the paper layer. To improve the recyclability of paper packaging laminates, it is advantageous when the sealing layer is made of PE when the base layer is mainly made of PE, or when the sealing layer is made of PP when the base layer is mainly made of PP. This allows for the production of paper packaging laminates with an exceptionally pure polymer content, which is advantageous for recyclability.

[0022] Advantageously, the sealing layer is also stretched. This allows for a reduction in the thickness of the sealing layer. On the other hand, it also allows the sealing layer to be co-extruded and stretched together with the barrier film, which simplifies manufacturing.

[0023] The present invention will be described in more detail below with reference to Figures 1-3, which illustrate exemplary, schematic, and non-limiting advantageous embodiments of the invention. [Brief explanation of the drawing]

[0024] [Figure 1] The first embodiment of the laminated material for paper packaging according to the present invention is shown. [Figure 2] This shows one design for an asymmetrical barrier film. [Figure 3] This shows one design for a symmetrical barrier film. [Modes for carrying out the invention]

[0025] Figure 1 shows a laminated paper packaging material 1 according to the present invention, comprising a paper layer 2 and a barrier film 3 bonded thereto, which provides the necessary barrier against water vapor, oxygen, and / or fragrance. A sealing layer 7 may be provided on the side opposite to the paper layer 2 of the laminated paper packaging material 1. The paper layer 2 is bonded to the barrier film 3 using an adhesive layer 9 made of a hydrophilic laminating adhesive. The typical thickness of the laminated paper packaging material 1 is from 50 μm to 150 μm.

[0026] Each layer of the laminated paper packaging material 1 will be described in more detail below.

[0027] Paper layer 2 is 30 to 360 g / m² 2 The basis weight, especially for flexible packaging materials, is 30-100 g / m². 2 It consists of paper having a basis weight of . Paper, as is known, is manufactured from fibrous materials, such as cellulose, wood pulp, or recycled paper. In the sense of this application, Pergamin paper is also understood as paper.

[0028] The paper layer is not coated on at least one side (the side facing the barrier film 3 in the paper packaging laminate 1). "Not coated" means that the paper is substantially uncoated on the aforementioned side, in particular, that no plastic material that can penetrate the paper, permeate the paper fibers, and bond with them has been applied to the paper. Such a plastic coating would be an inseparably bonded coating layer to the paper layer on this side. Therefore, specifically, the aforementioned side is not coated with, for example, barrier paint, sealing paint, or other coatings, nor is it extruded coated with a plastic layer. In contrast, layers consisting of layered silicates or minerals (clay coatings), which are often applied in the paper industry, can certainly exist, as they usually do not hinder paper recycling.

[0029] In the paper packaging laminate 1, the laminating adhesive used in the adhesive layer 9 is hydrophilic. Hydrophilic laminating adhesives have a strong interaction with water and are usually (but not always) water-soluble. The hydrophilic laminating adhesive used in the paper packaging laminate 1 according to the present invention loses its adhesiveness to water due to a chemical mechanism, for example, the breaking of hydrogen bonds or the dissolution of the laminating adhesive in water.

[0030] Hydrophilic laminated adhesives can be manufactured based on starch, sugar derivatives, cellulose, amino resins, (poly)acrylates, polyvinyl alcohol (PVOH), polyvinyl acetate, polyacrylic acid, maleic acid-modified ethylene copolymer, methylcellulose, carboxymethylcellulose, carboxy-functional polyester, polyethylene succinate, polybutylene succinate, ionomer, or hydrophilic polyurethane.

[0031] Similarly, hydrophilic lamination adhesives for extrusion lamination, such as (but not all) ethylene copolymers having polar group-containing comonomers, such as ethylene-vinyl acetate copolymer (EVA), ethylene-butyl acrylate (EBA), ethylene-acrylic acid copolymer (EAA), or polyethylene / polypropylene grafted with maleic anhydride (PE-G-Mah, PP-G-Mah), can also be used.

[0032] The aforementioned lamination adhesive is, naturally, selected to ensure sufficient adhesion between the paper layer 2 and the barrier film 3 in order to prevent undesirable delamination of the paper packaging laminate 1 during use. Using the adhesive layer 9, an adhesion between the paper layer 2 and the barrier film 3 should be achieved, preferably at least 1 N / 15 mm, and more preferably at least 1.5 N / 15 mm.

[0033] The adhesive strength is determined by a peel test. In the peel test, a test strip of the paper packaging laminate 1 is pulled apart at the free ends of the paper layer 2 and barrier film 3. At this time, these free ends are clamped in a tensile testing machine and pulled apart at a predetermined peel angle (e.g., 90°), and the force at this time is measured. If the width of the test strip is 15 mm, the adhesive strength value can be obtained as xN / 15 mm. In this case, the adhesive strength value is an approximately constant peel value and is not the maximum value at the beginning of the peel test, which occurs as a force peak at the start of the peel test. Generally, multiple peel tests are performed to determine the adhesive strength, and the measured adhesive strength is obtained as the average value from the individual measurements. The peel test is performed, for example, according to ASTM standard F904.

[0034] Since paper is used in the paper packaging laminate 1, a liquid laminating adhesive, particularly one dissolved in water or a suitable solvent, can be used to form an adhesive layer 9 between the paper layer 2 and the barrier film 3. After applying the liquid laminating adhesive and integrating the paper layer 2 and the barrier layer 3, the laminating adhesive is dried, during which water or solvent may diffuse into the paper. After drying, a bond is formed between the paper layer 2 and the barrier film 3, leaving behind the adhesive layer 9. However, non-liquid laminating adhesives can also be used to form the adhesive layer 9, as long as they are hydrophilic.

[0035] Similarly, an extrusion lamination method can also be considered, in which the molten laminating adhesive is extruded in a molten state onto the paper layer 2 or the barrier film 2, or both, at a high temperature exceeding 180°C, and then the paper layer 2 and the barrier film 3 are integrated. After the laminating adhesive has cured, this forms an adhesive layer 9.

[0036] The barrier film 3 consists of at least one stretched base layer 4, a bonding layer 5, and a barrier layer 6, which are mainly made of polyethylene (PE) or polypropylene (PP) (Figure 2). The thickness of the barrier film 3 is typically between 10 and 40 μm.

[0037] The barrier film 3 can be designed asymmetrically (as shown in Figure 2), comprising a base layer 4, a barrier layer 6, and a bonding layer 5 positioned between them, in which case the bonding layer 5 is directly bonded to the base layer 4 and the barrier layer 6. In the case of the asymmetric barrier film 3, the barrier layer 6 is preferably positioned on the side of the paper layer 2 in the paper packaging laminate 1 and is directly bonded to the uncoated surface of the paper layer 2 using an adhesive layer 9, but it may also be on the side of the sealing layer 7. However, the barrier film 3 can also be designed symmetrically (as shown in Figure 3). In this case, the barrier layer 6 would be bonded on both sides to the base layer 4 (which may be different) via the bonding layer 5. In the symmetric design, the uncoated surface of the paper layer 2 is directly bonded to one of the base layer 4 of the barrier film 3 via the adhesive layer 9.

[0038] In one possible embodiment, the barrier layer 6 is a barrier coating applied to the bonding layer 5 in the form of a metal coating, such as a metal coating using aluminum, or a coating consisting of silicon dioxide (SiOx) or aluminum oxide (AlOx). This embodiment is preferably used in the case of an asymmetrical barrier film 3. This barrier coating forms a thin barrier layer 6 on the bonding layer 5 that is only a few nanometers thick (typically about 10 to 50 nm). The metal coating can be performed, for example, by known vacuum metal coating. The SiOx or AlOx coating can be applied, for example, by chemical vapor deposition or vacuum deposition. Of course, other methods for forming the barrier coating are also possible. The barrier coating can also be additionally covered with a protective coating to protect against microcracking that may impair the barrier function. Using such a barrier coating, 2 cm 3 / m 2 Low oxygen transmission rate (OTR) of less than / d (23°C, 75% relative humidity, both sides) and 3cm 3 / m 2A low water vapour transmission rate (WVTR) (38 °C, 90% relative humidity, both sides) of less than / d can be achieved, where d represents one day, i.e. 24 hours.

[0039] In yet another possible embodiment, the barrier layer 6 is a layer made of a barrier polymer (used in both the asymmetric and symmetric barrier films 3), i.e. a layer made of a polymer having sufficient barrier properties, particularly against oxygen and / or aroma. The barrier polymer is preferably a polyamide (PA) or an ethylene - vinyl alcohol copolymer (EVOH). Preferably, EVOH is used as the barrier polymer. The barrier polymer has a thickness of up to 20%, preferably 5 to 10% of the total thickness of the barrier film 3, i.e. for example, if the thickness of the barrier film is from 10 to 40 μm, it is at most from 2 to 8 μm. Using a barrier polymer as the barrier layer 6 can achieve not only a low water vapour transmission rate (similar to or better than those described above), but also a low oxygen transmission rate (OTR) (23 °C, 75% relative humidity, both sides) of less than 2 cm 3 / m 2 / d and a high aroma barrier can also be achieved. There is no objective scale for the aroma barrier, and the function as an aroma barrier is determined subjectively by an odour test.

[0040] In the barrier film 3, when a barrier layer 6 made of a barrier polymer is provided, the barrier layer 6 can additionally be coated with a barrier coating in the asymmetric or symmetric barrier film 3, particularly, it can be metal-coated, for example, coated with aluminium, or coated with aluminium oxide or silicon oxide. Thereby, the barrier effect of the barrier film 3 can be further enhanced, particularly, thereby, the OTR and WVTR can be further significantly reduced, i.e. 1 cm respectively 3 / m 2It can be less than / d. In this embodiment as well, the barrier coating may be additionally covered with a protective coating.

[0041] Each base layer 4 is primarily made from polyethylene (PE) or polypropylene (PP), with each base layer 4 comprising at least 60% by weight, preferably at least 70% by weight, and very preferably at least 80% by weight of polyethylene or polypropylene. The higher the polyethylene or polypropylene content (i.e., the higher the purity of the base layer 4), the better the recyclability. The thickness of the base layer 4 is preferably 5 to 35 μm, in which case, base layers 4 of different thicknesses and / or different compositions can also be used in symmetrical barrier films 3. However, in symmetrical structures, preferably, both base layers 4 are designed using PE or PP as the same main component. Conventional additives (e.g., slip agents, antiblocking agents, fillers, etc.) can be added to the base layer 4. Different polyethylene or polypropylene species can also be used in each base layer 4 as mixtures or co-extruded products. Similarly, in addition to their respective main components PE or PP, the base layer 4 may contain polyolefin materials that are compatible with them.

[0042] For example, the polyethylene type for the base layer 4 is HDPE (0.94~0.97 g / cm³). 3 High-density polyethylene (MDPE), medium-density polyethylene (LDPE), and LDPE (0.915~0.935 g / cm³) have densities between 0.915 and 0.935 g / cm³. 3 Low-density polyethylene (LLDPE) with a density between 0.87 and 0.94 g / cm³ 3 Linear low-density polyethylene (MLLDPE) or linear low-density metallocene polyethylene (MLLDPE) having densities between 1 and 2 is considered. Preferably, HDPE or MDPE is used. As for the polypropylene species of the base layer 4, for example, atactic, syndiotactic, or isotactic PP is considered.

[0043] As polyolefin materials compatible with PE, basically any type of polyethylene is considered, and in particular ethylene copolymers, such as ethylene-vinyl acetate copolymer (EVA), ethyl methacrylate (EMA), ethylene / acrylic acid copolymer (MAA), or ethylene-butyl acrylate copolymer (EBA), are also considered. Similarly, propropylene (PP) or cycloolefin copolymer (COC) can also be used as PE-compatible polyolefin materials in amounts up to 20% by volume. In the case of PP, in order to achieve at least limited recyclability, preferably, polypropylene random copolymers, ethylene-containing polypropylene copolymers, or polypropylene homopolymers having ethylene as a conomomer (usually 5-15%) are used, which are well compatible with linear PE types, such as mLLDPE, LLDPE, or HDPE.

[0044] Suitable polyolefin materials for PP include PP copolymers, such as random copolymers and block copolymers. Similarly, the addition of up to 20% polyethylene has little impact on recyclability.

[0045] When a PE or PP-compatible polyolefin material is included in the base layer 4, in order to improve recyclability, the proportion of polyethylene (PE) or polypropylene (PP) as the main component in the base layer 4 is preferably at least 60% by weight, preferably at least 70% by weight, and very preferably at least 80% by weight (based on the base layer 4). In this case, PE or PP and the respective compatible polyolefin materials can exist as a mixture in the base layer 4.

[0046] However, the base layer 4 may also be constructed in a multilayer manner (by extrusion or co-extrusion) comprising one (or more) PE or PP layers and one (or more) layers made of a compatible polyolefin material.

[0047] A cavity-forming agent (Kavitierungsmittel) may be added to the main component of the base layer 4, which is PE or PP. In this case, the cavity-forming agent is added in an amount of 5 to 30% by weight, preferably 15 to 25% by weight, of the base layer 4. As the cavity-forming agent, polymers incompatible with PE or PP (i.e., polymers that remain isolated in the PE or PP matrix), such as polyamide (PA), polyester (e.g., PET or PBT), and polylactide (PLA) may be considered. Similarly, mineral cavity-forming agents, such as calcium carbonate or mica, can be used. The cavity-forming agent usually exists as a fine powder, which is embedded in the PE or PP matrix as a masterbatch before extrusion and then mixed with the PE or PP granules.

[0048] When a hollowed PE or PP layer is used in the base layer 4, it is preferably surrounded on one or both sides by a non-hollowed PE or PP layer. One possible structure of the base layer 4 of the laminate layer 3 would be, for example, a hollowed PE layer bonded (e.g., co-extruded) on one side with a non-hollowed PE layer. In this case, the hollowed PE layer is on the side of the paper layer 2 in the paper packaging laminate 1. Another preferred structure of the base layer 4 would be, for example, a hollowed PE layer bonded (e.g., co-extruded) on both sides with a non-hollowed PE layer. Similarly, there is also such a structure using PP as the main component in the base layer 4. The use of a hollowed layer in the base layer 4 can also improve the sealing properties of the paper packaging laminate 1.

[0049] The total amount of PE or PP, cavity-forming agents, any additives present, and any compatible polyolefin materials present in the base layer 4 is naturally only 100% by weight. In this case, the proportion of the main component, polyethylene or polypropylene, is important, and the proportions of the other materials must be adjusted accordingly.

[0050] At least the substrate layer 4 in the barrier film 3 is stretched in one or two directions, i.e., in the machine direction (MDO) (usually longitudinal or extrusion direction) and / or transverse direction (TDO) (rotated 90° relative to the machine direction). When a barrier polymer is used as the barrier layer 6 in the barrier film 3, preferably the entire barrier film is stretched. When the bonding layer 5 or barrier layer 6 is to be coated, it is stretched before coating. In this case, the stretching ratio in the machine direction and the transverse direction do not need to be the same. In this case, the stretching ratio in the machine direction is preferably at least 4:1 to 8:1. In this case, the stretching ratio in the transverse direction is preferably at least 5:1 to 10:1. Unidirectional MDO stretching is preferred because it is simpler than bidirectional stretching.

[0051] By stretching the barrier film 3, or at least the base layer 4 of the barrier film 3, the weight ratio of polyolefin (PE or PP) in the paper packaging laminate 1 can be kept low, because this stretching is the only way to produce a thin but still rigid film.

[0052] As is known, stretching a barrier polymer can significantly enhance its barrier properties. Stretching a barrier polymer can achieve a barrier value approximately 3 to 4 times higher than that of an unstretched barrier polymer of the same type, thereby allowing the use of a relatively inexpensive barrier polymer while maintaining the same barrier properties. This significantly reduces the cost of the paper packaging laminate 1.

[0053] The bonding layer 5 is used to bond the barrier layer 6 and the substrate layer 4. In this case, sufficient adhesion should be achieved, especially to prevent undesirable delamination of the barrier film 3. A suitable polar bonding layer 5 is preferably made of a polymer with increased polarity, such as a polymer based on a maleic anhydride-modified polyolefin (e.g., PE or PP), ethylene-vinyl acetate copolymer (EVA), ethylene / acrylic acid copolymer (EAA), ethylene-butyl acrylate (EBA), or similar polyolefin copolymer. The material of the bonding layer 5 is preferably selected to match the main component of the substrate layer 4. The thickness of the bonding layer 5 is a maximum of 10% of the total thickness of the barrier film 3, for example, 1 to 5 μm when the thickness of the barrier film 3 is 10 to 40 μm.

[0054] The sealing layer 7 is preferably polyethylene, such as LLDPE, LDPE, MDPE, or HDPE, when the main component of the base layer 4 is PE. Just as in the case of a multilayer sealing layer 7 made of the same or different PE types, a mixture of different PE types in the sealing layer 7 can also be considered. When the main component of the base layer 4 is polypropylene, the sealing layer 7 is preferably polypropylene, such as unstretched PP (CPP). In this case as well, the sealing layer 7 can be a mixture of different PPs and / or can be configured in a multilayer form. The thickness of the sealing layer 7 should be as thin as possible in terms of improved recyclability, and in particular, less than 50 μm, especially less than 30 μm.

[0055] Between the barrier film 3 and the sealing layer 7, a bonding layer 8, such as the one described above (as suggested in Figure 3), may be provided as needed to improve adhesion.

[0056] To ensure that the paper packaging laminate 1 is easily recyclable, the polymer component of the paper packaging laminate 1 (essentially the barrier film 3 and, if present, the sealing layer 7) should constitute between 10% and 50% by weight, preferably a maximum of 30% by weight, and particularly preferably a maximum of 20% by weight. Therefore, the paper packaging laminate 1 according to the present invention follows a different approach from the recommendations in the prior art, which require keeping the polymer content below 5% by weight. Nevertheless, to achieve good recyclability, the paper layer 2 is not coated on the barrier film 3 side and is bonded to the barrier film 3 using a hydrophilic adhesive layer 9.

[0057] When recycling the paper packaging laminate 1, it is typically subjected to a pulp process (soaking in water at a specified temperature for a specified time) after mechanical shredding. Due to the properties of the paper packaging laminate 1 according to the present invention, the paper layer 2 peels off from the barrier film 3, along with all layers and potential impurities of recycled paper, during the pulp process for recycling. The hydrophilic adhesive layer 9 reacts with water during the pulp process, losing its adhesive properties or dissolving completely in the water, resulting in the separation of the paper layer 2 from the barrier film 3. Thus, the paper layer 2 can dissolve in water to form pulp, from which recycled paper can be produced again. For recycling the paper packaging laminate 1, it is advantageous when the adhesive layer 9 sufficiently loses its adhesive properties or dissolves within a maximum of 20 minutes, preferably a maximum of 10 minutes, and particularly preferably a maximum of 5 minutes, at a water temperature of 40°C, resulting in the easy separation of the paper layer 2 and the barrier film 3 with the sealing layer 7.

[0058] The metal coating (if present) remains on the peeled barrier film 3 after separation during the pulp process in paper recycling, thus preventing the blackening of recycled paper that would inevitably occur when the paper surface is coated with a barrier metal.

[0059] The barrier film 3 (which may include a sealing layer 7) separated from the paper layer 2 during paper recycling can be fed into a further recycling process to allow for the reuse of the polyolefin (main component PE or PP) contained therein. By designing the barrier film 3 and the sealing layer 7 as purely as possible, using either PE or PP as the main component and compatible materials, the barrier film 3, which may include a sealing layer 7, can also be easily and cost-effectively reused in mechanical recycling using conventional methods. If the barrier layer 6 in the barrier film 3 is thin, the recyclability of the polyolefin stream discharged from the paper recycling pulp is not impaired.

[0060] The barrier film 3 is advantageously formed by co-extrusion, which allows for particularly simple and cost-effective manufacturing. Preferably, a known blow film method or flat film extrusion method is used. In this case, the individual layers of the symmetrical or asymmetrical layer structure of the barrier film 3 as described above (i.e., base layer(s) 4 and bonding layer(s) 5, optionally and barrier layer(s) consisting of the barrier polymer) are preferably co-extruded in a single step, with the exception of any coatings that may be present. After co-extrusion, the laminate is stretched in one or two directions. After this stretching, another barrier coating may be applied as a barrier layer 6 on the bonding layer(s) 5 or on the barrier polymer of the barrier layer(s) 6.

[0061] The barrier film 3 can also be co-extruded with the sealing layer 7 in a single process. In this case, the sealing layer 7 is also stretched together with the barrier film 3. Alternatively, the sealing layer 7 can be bonded to the stretched barrier film 3 by an extrusion lamination method (extrusion of the sealing layer 7 onto the barrier film 3) or a lamination method (bonding the barrier film 3 and the sealing layer 7 using a lamination adhesive). When laminating the sealing layer 7, the stretched sealing layer 7 can also be used.

[0062] Particularly preferably, the sealing layer 7 is directly integrated into the barrier film 3, for example by co-extrusion, when it is formed on the barrier film 3 on the side opposite to the barrier layer 6. This allows the sealing layer 7 to be designed to be thinner and the total proportion of polymer in the paper packaging laminate 1 to be reduced compared to the case where the sealing layer 7 is applied later. In addition, this simplifies manufacturing.

[0063] In this case, the stretching of the barrier film 3 (which may have a sealing layer 7) can be done in-line (i.e., directly after co-extrusion) or offline (i.e., at a later point after co-extrusion). In the case of bidirectional stretching, it can also be considered to stretch first in the machine direction and then in the transverse direction, or to stretch in both directions simultaneously. This stretching is typically carried out at a temperature about 10°C to 30°C lower than the lowest melting temperature of the plastic in the barrier film 3 or, optionally, the sealing layer 7, typically about 20°C lower (approximately 128°C to 130°C for HDPE). In either case, this stretching is carried out before coating, which may be done in the case of the barrier layer 6 and / or bonding layer 5.

[0064] In the case of PE or PP in which cavities are formed in the substrate layer 4 by unidirectional or bidirectional stretching, microcavities are generated in the PE or PP due to the cavity-forming agent, as is known. In this case, these microcavities increase the density of the substrate layer 4 from 0.4 to 0.85 g / cm³. 3 It was confirmed that the value could be significantly reduced. Therefore, barrier film 3 can be made lighter, which further reduces the polymer content.

[0065] The paper layer 2 is laminated with a barrier layer 3 which optionally includes a sealing layer 7. For this purpose, a hydrophilic laminating adhesive can be applied in liquid form to either the paper layer 2 or the barrier film 2, or both, for example, by roller application, printing, or spraying. The paper layer 2 and the barrier film 3 are then pressed together, for example, between two rollers, to produce a laminated paper packaging material 1. The laminating adhesive can then be dried, for example, by passing it through a heat tunnel, to form an adhesive layer 9, if necessary.

[0066] Alternatively, the paper layer 2 and the stretched barrier film 3 can be joined using an extrusion lamination method with a suitable laminating adhesive. In this extrusion lamination method, molten laminating adhesive is extruded onto the paper layer 2 or the barrier film 3, or both, and then the paper layer 2 and the barrier film 3 are pressed against each other, for example, between two rollers, to produce a paper packaging laminate 1. The laminating adhesive can then be cooled, which can usually be assisted by cooled rollers.

[0067] The sealing layer 7 of the paper packaging laminate 1 may be laminated even after the paper layer 2 and the barrier film 3 have been laminated.

[0068] In one exemplary embodiment, a barrier film 3 having a thickness of 10 to 40 μm is used, with a base layer 4 containing PE (at least 60% by weight of PE), preferably HDPE, as the main component accounting for at least 60% of the thickness of the stretched barrier film 3. A polar PE or PP material is used as the bonding layer 5 (depending on the main component of the base layer 4). A barrier layer 6 made of EVOH (barrier polymer) is bonded to this bonding layer 5. The barrier film 3 is co-extruded and then stretched in one or two directions. Additionally, the barrier polymer may be coated with a barrier coating (metal coating, SiOx, or AlOx) after stretching. In one alternative embodiment, a barrier coating is applied to the stretched base layer 4 with the bonding layer 5. The barrier film 3, at least partially stretched, is bonded to the paper layer 2 using an adhesive layer 9 made of a hydrophilic laminating adhesive. Additionally, the paper packaging laminate 1 may have a sealing layer 7 made of PE material on the side opposite to the paper layer.

Claims

1. 30 to 360 g / m ２ It consists of a paper layer (2) made of paper having a basis weight up to a certain amount, and a barrier film (3) bonded thereto. The barrier film (3) includes at least one substrate layer (4), a bonding layer (5), and a barrier layer (6), wherein the bonding layer (5) is disposed between the substrate layer (4) and the barrier layer (6). The base layer (4) is mainly composed of polyethylene or polypropylene, with a polyethylene or polypropylene ratio of at least 60% by weight, preferably at least 70% by weight, and very preferably at least 80% by weight of the base layer (4). - At least one of the substrate layers (4) of the barrier film (3) is stretched. Recyclable paper packaging laminate, - The proportion of the paper layer (2) is between 50% and 90% by weight of the laminated paper packaging material (1), preferably between 70% and 90% by weight, and - The barrier film (3) is bonded to the paper layer (2) using a hydrophilic adhesive layer (9), provided that the paper layer (2) is not coated on the barrier film (3) side. A recyclable paper packaging laminate characterized by the following features.

2. The recyclable paper packaging laminate according to claim 1, characterized in that the barrier film (3) is asymmetrically designed, comprising a base layer (4) bonded to the barrier layer (6) via a bonding layer (5).

3. The recyclable paper packaging laminate according to claim 2, characterized in that the barrier layer (6) is positioned on the paper layer (2) side and is bonded to the paper layer (2) via an adhesive layer (9).

4. The recyclable paper packaging laminate according to claim 1, characterized in that the barrier film (3) is symmetrically designed to have barrier layers (6) bonded to a base material layer (4) on both sides via bonding layers (5), and one of these base material layers (4) is bonded to a paper layer (2) via an adhesive layer (9).

5. The recyclable paper packaging laminate according to any one of claims 1 to 4, characterized in that the barrier layer (6) is formed as a barrier coating in the form of a metal coating or a coating of silicon oxide or aluminum oxide.

6. The recyclable paper packaging laminate according to any one of claims 1 to 4, characterized in that the barrier layer (6) is formed as a layer made of a barrier polymer, preferably a polyamide or an ethylene-vinyl alcohol copolymer.

7. The recyclable paper packaging laminate according to claim 6, characterized in that a barrier coating in the form of a metal coating or a silicon oxide or aluminum oxide coating is provided on a layer made of a barrier polymer.

8. The recyclable paper packaging laminate according to claim 6, characterized in that the barrier film (3) is stretched.

9. A recyclable paper packaging laminate according to any one of claims 1 to 8, characterized in that the barrier film (3) is bonded to the sealing layer (7) on the opposite side from the paper layer (2).

10. The recyclable paper packaging laminate according to claim 9, characterized in that when the base layer (4) is mainly made of polyethylene, the sealing layer (7) is made of polyethylene, or when the base layer (4) is mainly made of polypropylene, the sealing layer (7) is made of polypropylene.

11. The recyclable paper packaging laminate according to claim 9 or 10, characterized in that the sealing layer (7) is stretched.

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