Recyclable film with barrier layer

Abstract

The invention relates to a multi-layer, monoaxially stretched, recyclable film (1) for a laminate (7). The film (1) has outer layers (3) and at least one inner barrier layer (6), wherein a respective connecting layer (5) is arranged between same. A respective at least one further functional intermediate layer (4) is arranged between the outer layers (3) and the barrier layer (6).

Description

[0001] Recyclable film with barrier layer

[0002] Description

[0003] The invention relates to a multilayer, monoaxially stretched, recyclable film for a laminate, wherein the film has outer layers and at least one inner barrier layer, with a connecting layer arranged between each of them.

[0004] Current, commercially available plastic packaging is often made up of film laminates made of different layers, tailored to their application and function, such as polyolefins such as polyethylene (PE) and / or polypropylene (PP), often combined with polyethylene terephthalate (PET) and / or polyamide (PA). In addition, laminates made of different plastic layers are often combined with materials such as aluminum or paper.

[0005] Polyethylene has proven itself in the production of food packaging films, food bags, stretch films, shrink films, trash can liners, and shipping bags. Packaging prepared and / or raw foods, in particular, requires protective films with sufficiently low water vapor and oxygen permeability.

[0006] At the same time, the way in which plastic, and thus also food packaging film, is currently produced and disposed of can also be harmful to the environment under certain circumstances. The consequences range from high CO2 emissions to ocean pollution. To counteract this, the European Union aims to reduce the amount of plastic waste going to landfills as part of its Green Deal. By 2030, 55% of plastic packaging waste is to be recycled. To meet the challenges of recycling, packaging design must become increasingly sustainable. This can be achieved, for example, by implementing more mono-material constructions. The challenge here lies in achieving the very different properties of a package that were previously achieved by combining different plastic layers with different material bases using just one recyclable mono-material construction.

[0007] Such typical properties, and thus also requirements, for a packaging laminate include the barrier against water vapor, oxygen, and aroma penetration. Although polyethylene films can provide a sufficient barrier to water vapor due to their hydrophobic nature, they must be combined with additional layers or materials to improve the oxygen barrier properties. This function can be achieved in a packaging laminate using a barrier layer made of aluminum and / or a suitable barrier polymer, such as ethylene-vinyl alcohol copolymer (EVOH) and / or polyamide (PA).

[0008] Packaging itself is usually provided with a print that is visible from the outside. For this purpose, the packaging laminates are made of at least two films, with one film serving as a carrier film ideally adapted for the print, while the other film serves as a sealing film including a barrier layer.

[0009] EP 0 673 759 B1 already describes a multilayer packaging film consisting of a heat-sealing layer, layers of LLDPE, binding layers (and a barrier layer of EVOH), wherein the multilayer film was drawn biaxially in the machine direction and in the transverse direction with a stretch ratio of about 10.EP 2 106 342 B1 discloses a multilayer film comprising an ethylene-vinyl alcohol copolymer (EVOH) layer having a first surface and a second surface, a first tie layer adhesive bonded to the first surface and a second tie layer adhesive bonded to the second surface of the EVOH layer, at least one layer of high density polyethylene bonded to the first tie layer, and at least one polyethylene layer selected from the group consisting of a linear low density polyethylene and a high density polyethylene bonded to the second tie layer, wherein the multilayer film is post-oriented uniaxially in the machine direction with a draw ratio of greater than 5, and wherein the post-oriented film has a water vapor transmission rate of less than 3.5 g ■ mil / m. 2■ day and an oxygen transmission rate of less than 2.5 cm 3 ■ mil / m 2 ■ day.

[0010] EP 3 481 630 B1 describes a recyclable polyethylene film made of at least 80% polyethylene material and a maximum of 20% compatible polyolefin material, wherein the polyethylene film is less than 40 μm thick and has a central layer made of linear low-density polyethylene and / or linear metallocene low-density polyethylene and two outer layers made of high-density polyethylene which are connected to the central layer and surround the central layer, wherein the HDPE proportion of the polyethylene film makes up at least 60% by volume, preferably at least 70% by volume, very particularly preferably at least 80% by volume, and wherein the polyethylene film is stretched in at least one direction and the two outer layers together are at least three times as thick, preferably at least four times as thick, as the central layer.In order to achieve sufficient heat resistance, polypropylene or cyclo-olefin copolymer must be added to the outer layers of this film, which means that a mono-material construction is no longer possible.

[0011] EP 2 860 031 B1 discloses a machine-direction stretched multilayer film suitable for labels, comprising a core layer and two outer layers sandwiched around the core layer, wherein the core layer comprises a bimodal ethylene / 1-butene / C6-C12 alpha-olefin terpolymer having a density between 926 kg / m 3 up to 950 kg / m 3 and the two outer layers are unimodal HDPE with a density of more than 940 kg / m 3 up to 970 kg / m 3 include.

[0012] WO 2018 / 202479 A1 and WO 2020 / 038579 A1 disclose inventions of asymmetrically constructed, recycling-friendly, easily tearable packaging laminates with good barrier properties. The packaging laminates comprise a first laminate layer and a second laminate layer, wherein the first laminate layer is a co-extruded and machine-direction stretched composite of a substrate layer with an HDPE content of at least 60 vol%, a bonding layer, and a barrier layer made of a barrier polymer, preferably polyamide or ethylene-vinyl alcohol copolymer, with a thickness of a maximum of 20% of the total thickness of the first laminate layer. The bonding layer is arranged between the substrate layer and the barrier layer, and the first laminate layer is bonded to the second laminate layer at its barrier layer.The packaging laminate has excellent tearability in both directions, but this is not desirable in all packaging solutions.

[0013] The combination of the barrier function with the sealing requirements significantly limits the selection of possible sealing layers and creates major challenges in the production of packaging laminates. High-quality packaging laminates also usually feature an overprint created using a serial printing process, e.g., gravure or flexographic serial printing. Therefore, PET or PP film webs are often used as the printed film web in such film laminates. Currently, printed film webs with layer thicknesses of only 12 μm are used for this purpose. However, the construction of monolaminates made of polyethylene poses the problem of quality printability at such thin layer thicknesses.

[0014] The object of the present invention is to provide a film for a laminate that meets the requirements of a monomaterial construction and can ensure sufficient barrier properties. The film should be printable inexpensively and with excellent quality. To this end, the film should be particularly stiff and exhibit sufficient toughness. Furthermore, the film should have sufficient heat resistance. At least one film of the laminate should possess the necessary sealing properties. The film should be harmless to health and ecologically sustainable. Furthermore, the film should be odorless.

[0015] This object is achieved according to the invention by a film for a laminate according to the main claim. Preferred variants can be found in the subclaims, the description, and the drawings.

[0016] According to the invention, at least one further functional intermediate layer is arranged between the outer layers and the barrier layer.

[0017] The intermediate layer has to fulfill several functions. Ideally, it ensures favorable toughness while simultaneously maintaining a very rigid film structure. Only in this way can a high-quality print image be applied to the very thin film of the laminate. In a particularly advantageous variant, two functional intermediate layers are arranged one above the other, further enhancing the advantageous mechanical properties.

[0018] To ensure better adhesion of a high-quality print, the outer layers of the film are made of HDPE, which may also contain additives. The density of the HDPE of the outer layers ideally has a value of more than 0.941 g / cm³. 3, preferably more than 0.943 g / cm 3 , in particular more than 0.945 g / cm 3 on.

[0019] For example, the density of the HDPE of the outer layers is less than 0.97 g / cm 3 , preferably less than 0.965 g / cm 3 and / or its melt flow rate (at 190 °C at 21.6 kg) according to ISO 1133-1 is more than 5 g / 10 min, preferably more than 10 g / 10 min and / or less than 25 g / 10 min, preferably less than 20 g / 10 min.

[0020] In a variant of the invention, one or both outer layers may contain a small proportion of additives. For example, the proportion of additives in an outer layer is more than 0.5 wt.%, preferably more than 1.0 wt.%, in particular more than 1.5 wt.%, and / or less than 3.5 wt.%, preferably less than 3.0 wt.%, in particular less than 2.5 wt.%.

[0021] For example, the additives can include a highly transparent silica-based anti-blocking and IR filter masterbatch in a PE carrier resin and / or a processing aid to level the melt flowability. In one variant of the invention, the D97.5 of an additive is less than 12 pm, preferably less than 9 pm, in particular less than 6 pm. This still achieves an excellent anti-blocking effect, for example, while simultaneously supporting and / or protecting the barrier properties of the film.

[0022] Advantageously, the outer layers have a density higher than the functional intermediate layers by a factor, the value of the factor being more than 1.002, preferably more than 1.005, in particular more than 1.008 and / or less than 1.20, preferably less than 1.15, in particular less than 1.10.

[0023] In a particularly advantageous variant of the invention, the functional intermediate layers have a density of more than 0.91 g / cm 3 , preferably more than 0.92 g / cm 3 , in particular more than 0.93 g / cm 3 to and / or less than 0.940 g / cm 3 , preferably less than 0.939 g / cm 3 , in particular less than 0.938 g / cm 3 on.

[0024] The flow behavior of polyolefins is described using the melt flow rate according to ISO 1133-1, typically at a temperature of 190 °C for polyethylene and 230 °C for polypropylene under a load of 2.16 kg, 5 kg, or 21.6 kg. A higher melt index correlates with a lower average molecular weight of the polymer. At the same time, the higher the melt index of a polymer, the lower the melt viscosity, which is advantageous for high output from the extrusion line. On the other hand, polymers with a high molecular weight, i.e., a low melt index, are advantageous in terms of mechanical stability, especially tensile strength and toughness.Ideally, the HDPE of the outer layers has a melt flow rate according to ISO 1133-1 of more than 1.0 g / 10 min, preferably more than 1.25 g / 10 min, in particular more than 1.5 g / 10 min and / or less than 3.0 g / 10 min, preferably less than 2.0 g / 10 min, in particular less than 1.75 g / 10 min at 190 °C and 5 kg. Furthermore, the melt flow rate is more than 11 g / 10 min, preferably more than 13 g / 10 min, in particular more than 15 g / 10 min and / or less than 30 g / 10 min, preferably less than 20 g / 10 min, in particular less than 17 g / 10 min at 190 °C and 21.6 kg.

[0025] Preferably, the high-density polyethylene has a medium molecular weight and a particularly narrow molecular weight distribution, which leads to good bubble stability and processability. Furthermore, the outer layers exhibit excellent tensile strength and good elongation at break with a low tendency to fibrillation.

[0026] For example, high-density polyethylene has a tensile elasticity of more than 880 MPa, a tensile strength of more than 20 MPa, and a melting temperature of more than 129 °C. These special physical parameters result in a film that can fulfill the specified task.

[0027] In an alternative variant of the invention, the high-density HDPE has a melt flow rate according to ASTM D1238 of more than 0.1 g / 10 min, preferably more than 0.5 g / 10 min, in particular more than 0.8 g / 10 min and / or less than 3.0 g / 10 min, preferably less than 2.0 g / 10 min, in particular less than 1.0 g / 10 min at 190 °C and 2.16 kg. For example, this high-density HDPE has a density of more than 0.961 g / cm 3according to ASTM D792 and a tear strength according to Elmendorf of more than 40 g in MD and more than 165 g in TD. Advantageously, the polyethylene of the functional intermediate layers has a melt flow rate according to ISO 1133-1 of more than 1.0 g / 10 min, preferably more than 1.5 g / 10 min, in particular more than 1.9 g / 10 min and / or less than 4.0 g / 10 min, preferably less than 3.0 g / 10 min, in particular less than 2.1 g / 10 min at 190 °C and 5 kg.

[0028] Furthermore, the melt flow rate of the polyethylene of the functional intermediate layers is more than 20 g / 10 min, preferably more than 30 g / 10 min, in particular more than 40 g / 10 min and / or less than 65 g / 10 min, preferably less than 55 g / 10 min, in particular less than 45 g / 10 min at 190 °C and 21.6 kg. As a result, the polyethylene in the intermediate layers and in the film achieves high toughness and, at the same time, high stiffness values.

[0029] In one variant of the invention, the functional intermediate layers are formed from a bimodal polyethylene, preferably from a bimodal terpolymer, in particular from a bimodal ethylene / 1-butene / Ce-Ci2 alpha-olefin terpolymer. The combination of low molecular weight, high-density polymer chains and high molecular weight, low-density polymer chains results in a combination of stiffness and flexibility in the polyethylene of the functional intermediate layers. This enables an optimal balance between strength, impact resistance, stiffness, and processability of the resulting polyethylene of the functional intermediate layer.

[0030] Ideally, the barrier layer is formed as an ethylene-vinyl alcohol copolymer (EVOH) layer. Since the barrier properties of EVOH are superior to those of polyamide and PVDC, it is possible to make the barrier layer thin and stretched. This makes it possible to create a recyclable laminate, with the barrier layer accounting for a maximum of 5% of the total mass of the packaging laminate, allowing the laminate with barrier properties to be considered a monomaterial construction.

[0031] Advantageously, the density of the connecting layers has a value of less than 0.915 g / cm 3 , preferably less than 0.910 g / cm 3 , in particular less than 0.905 g / cm 3 The bonding layers are based on LLDPE grafted with maleic anhydride and improve the adhesion between the PE layers and the EVOH layer in blown film production.

[0032] In a particularly advantageous variant of the invention, the connecting layer is made of a polyethylene whose density is more than 0.880 g / cm 3 , preferably more than 0.900 g / cm 3 and / or less than 0.940 g / cm 3 , preferably less than 0.920 g / cm 3 and / or whose melt flow rate (at 190 °C at 2.16 kg) according to ASTM D 1238 is more than 0.1 g / 10 min, preferably more than 1.0 g / 10 min and / or less than 5.0 g / 10 min, preferably less than 3.0 g / 10 min.

[0033] Ideally, the melt flow rate (at 190 °C at 2.16 kg) of the bonding layer is similar to the melt flow rate of the functional intermediate layer according to ASTM D 1238. The melt flow rates of the bonding layer and the functional intermediate layer differ by a factor of less than 1.5, preferably less than 1.4, and in particular less than 1.3. This particularly improves the adhesion and embedding of the barrier into the polyethylene layer composite and represents a key inventive feature of the laminate construction.

[0034] The haze value is a measure of the haziness or gloss of transparent films. The method for measuring the haze value is described in the ASTM D 1003 standard and DIN EN ISO 2813. Ideally, the film should have a gloss according to DIN EN ISO 2813 of less than 7%, preferably less than 6%, especially less than 5%. This gives the laminate and film a particularly high-quality appearance.

[0035] The gas permeability of films is determined according to DIN EN ISO 2556 under atmospheric pressure. A film test specimen separates two chambers, one of which contains the test gas at atmospheric pressure, while the other, with a known initial volume, is evacuated of air until a near-vacuum is reached. The amount of gas flowing through the test specimen from one chamber to the other is determined as a function of time by measuring the pressure increase in the second chamber with a manometer.

[0036] Advantageously, the film has an oxygen transmission rate of less than 10 cm 3 / m 3 ■ Day ■ bar, preferably less than 6 cm 3 / m 3 ■ day ■ bar, especially less than 2 cm 3 / m 3 ■ day ■ bar, measured at 23 °C and 0% rH. Thus, the film and the packaging laminate have excellent barrier properties for storing sensitive foods.

[0037] The determination of water vapor permeability for dry or moisture-sensitive goods is carried out according to DIN 53116 using a gravimetric measuring method. A test container filled with a desiccant is sealed with a film sample and exposed to a defined test climate. The amount of water permeating through the sample is determined by weighing. The water quantity can be in the range of 1 - 200 g / (m 2■ d) be detected. The detection limit also depends on the sample properties and the sample thickness. In a particularly advantageous variant of the invention, the film has a water vapor permeability of less than 50 g / m 2 , preferably less than 25 g / m 2 , in particular less than 5 g / m 2 in 24 hours according to ASTM D6701-01. This makes the film and laminate particularly suitable for packaging perishable foods.

[0038] Advantageously, the film is monoaxially stretched in the machine direction by a factor of more than 2.0, preferably by a factor of more than 3.0, in particular by a factor of more than 4.0, and / or by a factor of less than 7.0, preferably by a factor of less than 6.5, in particular by a factor of less than 6.0. Among other things, the stretching imparts the film's particularly advantageous mechanical properties.

[0039] The film according to the invention is ideally designed as a carrier film for printing combined with excellent barrier properties. The special selection of polymers and the design in a seven- or nine-layer variant result in a particularly thin film that nevertheless exhibits convincing mechanical properties, even in a monomaterial construction. Despite the thin design, the rigidity and toughness, achieved in particular by the functional intermediate layers, result in excellent printability. In addition, the barrier function, which is usually integrated into the sealing layer, is already implemented in the carrier film, enabling the selection of particularly thin sealing layers that can be sealed at low temperatures.

[0040] A film made of pure HDPE as described in DE 10 2005 003922A 1 would be just stiff enough for printing and heat-resistant as a print substrate, but not tough enough for use as a laminate and would tend to splice in the direction of stretching. The inventive film structure with the functional intermediate layers allows these quite contradictory properties to be combined.

[0041] A frequently used method for printing on film is flexography. This is a direct relief printing process, also known as a web-fed rotary printing process. The flexible printing plates, made of photopolymer or rubber, are used in combination with low-viscosity printing inks. The raised areas of the printing form carry the image. The advantages lie in the cost-effectiveness due to the utilization of a large printing width and high printing speed, as well as the availability of inexpensive printing inks. The printing tools essentially consist of photopolymer printing plates and / or laser-engraved elastomer sleeves. Large print runs can be produced cost-effectively with flexography.

[0042] In a particularly advantageous variant, an imprint is applied directly to an outer layer of the film. The imprint can be applied on the side facing away from the packaged product or as a counterprint between the film and the layer. The imprint can be implemented as a printed motif. In the film sector, the term "print motif" refers to the thematic design element of an imprint. If necessary, manufacturer-identifying print motifs can also be included in the imprint.

[0043] Preferably, the print is applied to an outer layer of the film using a flexographic printing process, whereby all common printing processes are in principle suitable for this purpose and are expressly included in the invention.

[0044] The film thickness was measured according to DIN 53370 and reported as an average value. Advantageously, the film has a thickness of less than 60 μm, preferably less than 50 μm, in particular less than 40 μm, and / or more than 5 μm, preferably more than 10 μm, in particular more than 15 μm. Thus, the film is designed to be as thin and material-efficient as possible, yet still suitable for applying high-quality printing.

[0045] In a particularly advantageous variant of the invention, the multi-layer structure of the film is symmetrical, whereby the printability of both outer layers can be realized and thus a flexible variation can be made between the printing arrangement on the outside or the counter printing.

[0046] To ensure recyclability and thus also sorting in modern waste separation plants, such as the sink-float process, the density of the film is less than 0.99 g / cm 3 , preferably less than 0.98 g / cm 3 , in particular less than 0.97 g / cm 3 and / or more than 0.60 g / cm 3 , preferably more than 0.70 g / cm 3 , in particular more than 0.80 g / cm 3 .

[0047] Heat sealing is a common method for creating seals and seams in flexible packaging. Adhesive systems are also occasionally used. There are many different types of heat seals. The most common, especially for films, are thermal sealing, bar sealing, and impulse sealing.

[0048] Suitable film layers for heat sealing are LDPE and LLDPE, which can then be sealed with the film to form a laminate. LDPE exhibits better heat sealing properties than LLDPE. It seals at lower temperatures, seals over a wider temperature range, and exhibits better hot tack, largely due to its long-chain branching. Metallocene LLDPE with higher alpha olefins was developed to address this disadvantage of LLDPE. Another approach to achieving the best mix of properties for a specific application is to blend LLDPE and LDPE.

[0049] Thermal sealing uses two heated rods that apply pressure to the films to be sealed while simultaneously conducting heat to the interface, melting the films at those points. This pressure ensures good contact between the films and assists the penetration of the molten, viscous materials at the interface. After sufficient sealing time, the pressure of the rods is released, releasing the films. Therefore, the hot tack of the film material is critical for forming an adequate seal. The full strength of the seal develops as the film material cools, but the initial strength must be sufficient to maintain the integrity of the seal during cooling.

[0050] Sealing bars typically have rounded edges to prevent punctures, and one bar is often provided with an elastic surface to ensure even pressure during sealing. The sealing jaws are usually not flat, but rather serrated, creating a patterned seal. In thermal sealing variants, only one bar is heated and the other is not. Another variant uses heated rollers instead of bars; for example, a bag is sealed as it passes through the rollers.

[0051] To design a film with particularly advantageous sealing properties, at least one outer layer and / or outer layer contains a proportion of polypropylene, wherein the proportion is more than 5% by weight, preferably more than 10% by weight, in particular more than 15% by weight, and / or less than 50% by weight, preferably less than 40% by weight, in particular less than 30% by weight. The proportion of polypropylene increases the heat resistance and thus also the temperature at which the film can be sealed without undermining the recyclability of the film.

[0052] Ideally, the layer has a thickness of more than 10 μm, preferably more than 15 μm, in particular more than 20 μm, and / or less than 100 μm, preferably less than 80 μm, in particular less than 60 μm. Thus, depending on the application of the polyethylene film, a thin layer or, for example, a thick layer when enclosing liquids can be realized.

[0053] Advantageously, the layer used to seal the film into a laminate is made of LDPE or LLDPE. Low-density polyethylene (LDPE) is a thermoplastic made from the monomer ethylene. LDPE has more branches (at about 2% of the carbon atoms) than HDPE, so its intermolecular forces are weaker, its tensile strength is lower, and its elasticity is higher. The side branches mean that the molecules are less densely packed and less crystalline, which is why the density is lower.

[0054] The production of LLDPE is initiated by transition metal catalysts, particularly Ziegler- or Philips-type catalysts. The actual polymerization process can be carried out either in the solution phase or in gas-phase reactors. Typically, octene is the comonomer in the solution phase, while butene and hexene are copolymerized with ethylene in a gas-phase reactor. LLDPE has higher tensile strength and higher impact and puncture resistance than LDPE. It is very flexible and expands under load. It can be used to produce thinner films that have better resistance to stress cracking. It has good chemical resistance. It has good electrical properties. However, it is not as easy to process as LDPE, has lower gloss, and a narrower heat-sealing range.

[0055] In a particularly advantageous variant of the invention, the polyethylene film, including the layer, is made entirely of polyethylene. Polyethylene (PE) is a thermoplastic produced by chain polymerization of petrochemically produced ethylene. Polyethylene is semi-crystalline and non-polar. Thus, the film meets the requirements of the Plastics Pact, is based on a monomaterial construction, and is recyclable.

[0056] In an alternative variant of the invention, the film has at least one additional outer layer made of an ethylene-vinyl alcohol copolymer (EVOH) and / or polyamide (PA). This additional layer can be formed as an outer layer, to which the print adheres better due to the higher polarity of the outer layer. At the same time, this additional outer layer improves the heat resistance and stiffness of the film. For this purpose, the additional layer made of EVOH and / or PA is particularly thin, so that the material content of the overall film is particularly low and the film is considered a monomaterial construction for recycling purposes.

[0057] In a variant of the invention, the film comprises at least one further outer layer to produce a matt finish on the film surface.

[0058] For example, the additional outer layer contains no fillers, and the film has a haze value according to ASTM D1003 of more than 65%, preferably more than 75%, in particular more than 85%, due to the additional outer layer. The additional outer layer has, for example, a thickness of more than 4 μm and / or less than 10 μm.

[0059] For example, the additional outer layer can be arranged on the side of the film facing away from the print and / or visible from the outside. The matte surface gives the film a favorable appearance.

[0060] In an alternative variant of the invention, at least one of the layers can contain a proportion of LLDPE in order to increase the elasticity and thus also the Elmendorf tear strength of the film.

[0061] According to the invention, the process for producing a laminate comprises several steps. First, various compositions of the polymer components are prepared, which are then extruded into a film web with at least seven, ideally nine layers. The polymer mixtures differ with regard to the respective layers and the barrier layer. According to the invention, at least one further, functional intermediate layer is arranged between the outer layers and the barrier layer. Advantageously, the film web is stretched monoaxially in the machine direction, whereby the favorable properties with regard to the total density below 0.99 g / cm 3 , transparency and printability, stiffness and toughness, as well as the barrier properties of the film are achieved. The film web can then be directly printed and laminated with a sealing layer.

[0062] Ideally, extrusion is carried out as a blow molding process, which promotes the development of advantageous film characteristics, such as stiffness. The film is produced by monoaxial stretching with a machine direction orientation (MDO) by heating the film to a temperature slightly below its melting point and stretching it in a specific orientation. Stretching can also be performed directly after extrusion, when the film web is still at a temperature slightly below its melting point.

[0063] In an advantageous variant of the invention, the film is stretched monoaxially in the machine direction by a factor of more than 2.0, preferably by a factor of more than 3.0, in particular by a factor of more than 4.0 and / or by a factor of less than 7.0, preferably by a factor of less than 6.5, in particular by a factor of less than 6.0. This gives the film advantageous stiffness and favorable transparency, and at the same time, the density of the film has a value of less than 0.99 g / cm 3 .

[0064] According to the invention, the laminate is used as recyclable and oxygen-impermeable packaging, in particular as packaging for sensitive and perishable food.

[0065] Further advantages and features of the invention will become apparent from the description of an embodiment with reference to drawings and from the drawings themselves.

[0066] This shows

[0067] Fig. 1 shows a schematic structure of the laminate according to the invention,

[0068] Fig. 2 shows a schematic structure of the laminate with a reverse-printed imprint. Fig. 1 shows a schematic structure of the laminate 7, which is formed from film 1 and layer 8. An imprint 2 is arranged directly on an outer layer 3 of film 1. The imprint 2 serves to identify the article to be packaged, as well as for visual recognition and to support the brand image of the article brand.

[0069] In this embodiment, film 1 is designed with nine layers in a symmetrical structure. The innermost layer is formed as a barrier layer 6 and consists of an ethylene-vinyl alcohol copolymer. The properties of the inner barrier layer 6 result in a film 1 with an oxygen transmission rate of less than 2 cm³. 3 / m 3■ Day ■ bar, measured at 23 °C and 0% rH. In addition, the film 1 is almost impermeable to water vapor due to the inner barrier layer 6, with a water vapor permeability of less than 5 g / m 2 in 24 hours according to ASTM D6701-01. The thickness of barrier layer 6 in this design variant is approximately 14 pm before stretching.

[0070] The barrier layer 6 is surrounded by a connecting layer 5, which consists of an LLDPE whose density is 0.910 g / cm 3 and whose melt flow rate (at 190 °C at 2.16 kg) according to ASTM D 1238 is 2.5 g / 10 min. In this embodiment, the bonding layer 5 is formed with a maleic anhydride-grafted polyethylene to create a bond between the other polyethylene-based layers and the EVOH-based barrier layer 6. The thickness of the bonding layer 5 in this embodiment is approximately 8.5 μm before stretching.

[0071] Between the outer layers 3 and the connecting layers 5, two functional intermediate layers 4 are arranged, which realize the toughness despite the enormous stiffness of the film 1. The intermediate layers 4 consist entirely of a polyethylene whose density is 0.937 g / cm 3 and whose melt flow rate (at 190 °C at 5 kg) according to ISO 1133 is 2 g / 10 min. The thickness of a functional intermediate layer 4 in this embodiment is approximately 14 pm before stretching.

[0072] The two outer layers 3 of the film 1 consist of a proportion of additives and HDPE. In the illustrated embodiment, the HDPE content is 98 wt.% and its density is 0.946 g / cm 3 and whose melt flow rate (at 190 °C at 5 kg) according to ISO 1133 is 1.6 g / 10 min.

[0073] The layer thickness of the outer layers 3 before stretching in this embodiment is 15 - 17 pm, whereby the outer layer 3, which is arranged for printing 2, is somewhat thicker.

[0074] The nine-layer film 1 has a thickness of 120.5 μm after blow extrusion. After monoaxial stretching by a factor of 4.82, the thickness is 25 μm, with a density of 0.95 g / cm 3 . Layer 8 is made of LDPE.

[0075] Fig. 2 shows a further schematic structure of the laminate 7, which is formed from the film 1 and the layer 8. The film 1 and the layer 8 correspond to the illustration and description of Fig. 1. The print 2 is arranged directly on an outer layer 3 between the film 1 and the layer 8 and is applied by means of a counter-printing process.

[0076] In the embodiment of Fig. 2, the higher density polyethylene of the outer layers 3 and the outer intermediate layers 4 is designed as a HDPE, the density of which is 0.962 g / cm 3 and whose melt flow rate (at 190 °C at 2.16 kg) according to ASTM 1238 is 0.85 g / 10 min.

[0077] In addition, the film 1 has an optional outer layer 9 made of an ethylene-vinyl alcohol copolymer (EVOH). The print 2 adheres better to the additional outer layer 9 due to its higher polarity. In the illustrated embodiment, the thickness of the outer layer 9 after stretching is 4 μm and is made of a SoarnoL™ from Mitsubishi Chemicals.

Claims

Recyclable film with barrier layer Multi-layer, monoaxially stretched, recyclable film (1) for a laminate (7), wherein the film (1) has outer layers (3) and at least one inner barrier layer (6), wherein a connecting layer (5) is arranged between each of the outer layers (3) and the barrier layer (6), characterized in that at least one further, functional intermediate layer (4) is arranged between each of the outer layers (3) and the barrier layer (6). Film according to claim 1, characterized in that the outer layers (3) have a density higher by a factor than the functional intermediate layers (4), wherein the value of the factor is more than 1.002, preferably more than 1.005, in particular more than 1.008 and / or less than 1.20, preferably less than 1.15, in particular less than 1.

10. Film according to claim 1 or 2, characterized in that the density of the outer layers (3) has a value of more than 0.941 g / cm 3, preferably more than 0.943 g / cm 3 , in particular more than 0.945 g / cm 3 has.

4. Film according to one of claims 1 to 3, characterized in that the density of the functional intermediate layers (4) has a value of more than 0.91 g / cm 3 , preferably more than 0.92 g / cm 3 , in particular more than 0.93 g / cm 3 and / or less than 0.940 g / cm 3 , preferably less than 0.939 g / cm 3 , in particular less than 0.938 g / cm 3 has.

5. Film according to one of claims 1 to 4, characterized in that the functional intermediate layers (4) are formed from a bimodal polyethylene, preferably from a bimodal terpolymer, in particular from a bimodal ethylene / 1-butene / C6-C12-alpha-olefin terpolymer.

6. Film according to one of claims 1 to 5, characterized in that the density of the connecting layers (5) has a value of less than 0.915 g / cm 3 , preferably less than 0.910 g / cm 3 , in particular less than 0.905 g / cm 3 has.

7. Film according to one of claims 1 to 6, characterized in that the barrier layer (6) is formed as an ethylene-vinyl alcohol copolymer layer. Film according to one of claims 1 to 7, characterized in that the connecting layer (5) comprises a maleic anhydride-modified polyethylene and preferably a polyethylene, the density of the connecting layer (5) being more than 0.880 g / cm 3 , preferably more than 0.900 g / cm 3 and / or less than 0.940 g / cm 3 , preferably less than 0.920 g / cm 3and / or whose melt flow rate (at 190 °C at 2.16 kg) according to ASTM D 1238 is more than 0.1 g / 10 min, preferably more than 1.0 g / 10 min and / or less than 5.0 g / 10 min, preferably less than 3.0 g / 10 min. Film according to one of claims 1 to 8, characterized in that the melt flow rate (at 190 °C at 2.16 kg) according to ASTM D 1238 of the connecting layer (5) is similar to the melt flow rate of the functional intermediate layer (4), the melt flow rates of the connecting layer (5) and the functional intermediate layer (4) differing by a factor of less than 1.5, preferably less than 1.4, in particular less than 1.

3. Film according to one of claims 1 to 9, characterized in that the film (1) has a gloss according to DIN EN ISO 2813 of less than 7%, preferably less than 6%, in particular less than 5%. Film according to one of claims 1 to 10, characterized in that the film (1) has an oxygen transmission rate of less than 10 cm 3 / m 3 ■ Day ■ bar, preferably less than 6 cm 3 / m 3 ■ day ■ bar, especially less than 2 cm 3 / m 3 ■ day ■ bar, measured at 23 °C and 0% rH. Film according to one of claims 1 to 11, characterized in that the film (1) has a water vapor permeability of less than 50 g / m 2 , preferably less than 25 g / m 2 , in particular less than 5 g / m 2in 24 h according to ASTM D6701-01. Film according to one of claims 1 to 12, characterized in that the film (1) is stretched monoaxially in the machine direction by a factor of more than 2.0, preferably by a factor of more than 3.0, in particular by a factor of more than 4.0 and / or by a factor of less than 7.0, preferably by a factor of less than 6.5, in particular by a factor of less than 6.

0. Film according to one of claims 1 to 13, characterized in that an imprint (2) is arranged directly on an outer layer (3) of the film (1).

15. Film according to one of claims 1 to 14, characterized in that the film (1) has a thickness of less than 60 pm, preferably less than 50 pm, in particular less than 40 pm and / or more than 5 pm, preferably more than 10 pm, in particular more than 15 pm.

16. Film according to one of claims 1 to 15, characterized in that the density of the film (1) is less than 0.99 g / cm 3 , preferably less than 0.98 g / cm 3 , in particular less than 0.97 g / cm 3 and / or more than 0.60 g / cm 3 , preferably more than 0.70 g / cm 3 , in particular more than 0.80 g / cm 3 amounts.

17. Film according to one of claims 1 to 16, characterized in that the multilayer structure of the film (1) is symmetrical.

18. Film according to one of claims 1 to 17, characterized in that the film (1) has at least one additional outer layer (9) made of an ethylene-vinyl alcohol copolymer (EVOH) or polyamide (PA). Film according to one of claims 1 to 18, characterized in that the film (1) comprises at least one further outer layer for producing a matt finish, which outer layer does not contain any fillers, the film (1) thereby having a haze value according to ASTM D1003 of more than 65%, preferably more than 75%, in particular more than 85%. Film according to one of claims 1 to 19, characterized in that at least one outer layer (3) has a proportion of polypropylene, the proportion being more than 5% by weight, preferably more than 10% by weight, in particular more than 15% by weight and / or less than 50% by weight, preferably less than 40% by weight, in particular less than 30% by weight.

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