Film packaging having cavities and being oriented in the direction of movement of the machine

Abstract

The invention relates to a recyclable, cold-sealing packaging (11, 13) comprising a first film (1) and a cold-sealing compound (2) and a print (4). The film (1) consists of a substantially homogeneous polyolefin, is stretched monoaxially in the machine direction and comprises at least two layers (5, 6). At least one layer (6) includes an inorganic filler material for producing cavities in the layer.

Description

[0001] MACHINE DIRECTION-ORIENTED FILM PACKAGING WITH CAVITIES

[0002] Description

[0003] The invention relates to a recyclable, cold-sealing packaging comprising at least a first film and a cold-sealing compound and a print, wherein the film is formed from a largely pure polyolefin, is stretched monoaxially in the machine direction and has at least two layers

[0004] Packaging is important for protecting products and / or extending the shelf life of food. The range of different packaging options is broad, ranging from paper packaging, glass and metal packaging, to composite packaging and plastic packaging.

[0005] The properties of low mass, durability, and longevity make plastics ideal for food packaging. Polyethylene (PE) and polypropylene (PP)-based packaging are particularly environmentally advantageous, as they are particularly easy to recycle.

[0006] Packaging is usually understood as a multi-layered, one-piece arrangement of partially different films, which can be produced by extrusion. The term laminate refers to the bonding of one film to another to form a packaging unit. A print or printed image can be placed between the films.

[0007] At the same time, the way plastic packaging is currently produced and disposed of can also be harmful to the environment. The consequences range from high CO2 emissions to ocean pollution. To counteract this, the European Union aims to reduce the landfilling of plastic waste as part of its Green Deal. By 2030, 55% of plastic packaging waste is to be recycled.

[0008] The term "mechanical recycling" refers to the processing of plastic waste into secondary raw materials or products in which the chemical bonds of the plastics are not broken down. The waste is mechanically shredded and melted using an extruder. Plastic granules are then produced again in the same process. This form of recycling is particularly suitable for waste streams of a relatively clean plastic type.

[0009] Of course, this also presents challenges for recycling. Plastics streams consist of a mix of materials, often with a high degree of contamination. The effort required for collection, sorting, washing, and recycling is expensive and results in a raw material of limited quality. This makes it commercially unattractive to use the recycled raw materials from these streams in new products.

[0010] The focus will therefore also be on more sustainable product design, such as the construction of more mono-materials, better separation at source and further technical developments around automatic sorting and decolorization, which will make mechanical recycling of these waste streams more attractive.

[0011] Now that many European countries have signed the European Plastics Pact, this situation could soon improve. According to this pact, all packaging and single-use plastics must be designed to be reusable or recyclable by 2025. The term "cold seal" refers to the sealing of a plastic package at ambient temperature, typically 15-26°C, as opposed to a high-temperature sealing polymer, which seals upon application of heat and pressure. Due to their ability to form seals without heat, cold seal compounds are ideal for packaging heat-sensitive products such as ice cream, baked goods, and confectionery. Furthermore, cold seal pressure sensitive adhesives enable faster packaging speeds than heat sealing methods.

[0012] Cold-sealable compositions are adhesives that feel non-tacky after application and drying to a substrate, but adhere to each other when pressed together with pressure at room temperature. Because of their non-stick properties, coated substrates can be rolled up and stored until use without adhesion to the opposite side of the carrier substrate, which is preferably provided with a release coating. Polymer dispersions based on natural rubber latex are typically used for cold-seal adhesives.

[0013] WO 2014 / 154507 A1 describes the use of a polymer dispersion for cold sealing, wherein the polymer dispersion contains a polymer dispersed in water and having a glass transition temperature in the range from -20 to +10°C, which can be prepared by emulsion polymerization of radically polymerizable monomers in the presence of at least one polymeric protective colloid and wherein the polymer is formed from 0.05 to less than 1% by weight of a monomer M selected from the group consisting of (meth)acrylate monomers having a substituent of the formula wherein X is CH2, O, NH or NR and R is a Ci to C4 alkyl group.US 7,569,279 B2 discloses a packaging film with a cold seal release film comprising a cold seal release layer for releasably engaging a cold seal adhesive. The packaging film has a cold seal receiving layer opposite the cold seal release layer, the cold seal receiving layer retaining the cold seal adhesive thereon, and the cold seal adhesive retained on the receiving layer can releasably engage the cold seal release layer. The cold seal release layer contains a silicone oil lubricant and is oxidatively treated.

[0014] DE 602 08 583 T3 describes a polyolefin multilayer film with a polyolefin core layer and a first polyolefin cover layer adjacent to the core layer, which provides a cold-seal-accepting surface for a cold-seal adhesive. The first polyolefin cover layer contains no thermoplastic or natural rubber. The first polyolefin cover layer comprises a mixture of a random ethylene-propylene copolymer in an amount of 50-90 wt.% of the cover layer and a metallocene-catalyzed plastomer in an amount of 10-50 wt.% of the cover layer.

[0015] WO 2020 / 098947 A1 discloses a recycling-friendly, easily tearable packaging laminate with good barrier properties and low density, comprising a first laminate layer and a second laminate layer. The first laminate layer is a co-extruded and stretched composite of a cavitated substrate layer with 5-30 wt.% cavitating agent and a PE content of at least 60 wt.%, a bonding layer, and a barrier layer made of a barrier polymer.

[0016] The object of the present invention is to provide packaging that meets the requirements of the Plastics Pact 2025 and is fully recyclable. The packaging should also be suitable for packaging food. Furthermore, the packaging should be designed to be very rigid and opaque. The packaging should be shrink-free. The packaging should be harmless to health and ecologically sustainable. Furthermore, the packaging should not emit any odors. Furthermore, the packaging should have a pleasant feel.

[0017] This object is achieved according to the invention by a recyclable, cold-sealed packaging, a method, and two uses according to the independent main claims. Preferred variants can be found in the dependent claims, the description, the exemplary embodiment, and the drawings.

[0018] According to the invention, at least one layer comprises an inorganic filler for creating cavities in the layer.

[0019] In abstract terms, a cavity is an empty or gas-filled space inside something solid. The space is thus surrounded by a solid boundary that separates it from the outside. In the case of a polymer film, the space is separated from the outside by polymer material.

[0020] Preferably, one cavity and / or a plurality of cavities and / or all cavities of the layer can be designed in the form of vacuoles.

[0021] The inorganic, solid filler serves to create these cavities or vacuoles through monoaxial stretching after extrusion. This gives the film and / or packaging a beneficial opacity.

[0022] Opacity is the opposite of transparency. It is a measure of the light impermeability or opacity expressed as a percentage. Specifically, the opacity of a completely opaque film is 100%, and a completely or fully transparent film has an opacity of 0%.

[0023] In a particularly advantageous variant, the film has an opacity according to DIN 53416 of more than 80%, preferably more than 90%, especially more than 95%. This allows the film to be printed directly and eliminates the need for an opaque layer underneath the print, which must first be created or applied.

[0024] In a highly advantageous embodiment of the invention, the film for packaging products and / or foodstuffs does not contain titanium dioxide to create opacity. This embodiment particularly satisfies the requirements of environmental and health protection.

[0025] The film, which is virtually free of titanium dioxide, complies with both the European Chemicals Regulation REACH and the amending regulation to the CLP Regulation. The film can therefore be described as free of harmful substances.

[0026] In a particularly advantageous variant of the invention, the filled layer is formed as the inner layer. The inner layer is preferably surrounded by two unfilled layers. This creates a three-layer film in the most minimalist version.

[0027] Surrounding the filled layer with unfilled layers ensures both the containment and the sealing of the cavities to the outside. This ensures that no cavity has a direct and / or indirect connection to the outside.

[0028] In further variants of the invention, the filled layer can be surrounded by several unfilled layers, preferably resulting in a symmetrical film structure. This means that the filled layer is surrounded on both sides by the same number of unfilled layers. This preferably results in a five-layer, seven-layer, or nine-layer film.

[0029] Hard and inorganic fillers are particularly suitable for the film according to the invention. The proportion of fillers is such that stretching results in only microporous cavities that do not exhibit a network of interconnections.

[0030] The filler content can be determined using well-known measurement methods such as ashing. A sample with a known initial weight is heated to a temperature at which the polymer thermally decomposes but the filler does not. A temperature of 560 °C, for example, has proven effective for this purpose. The sample weight is then measured again. The polymer content per square meter can be calculated from the difference between the initial and final weight.

[0031] As an alternative to ashing, a TGA measurement is possible, in which the weight of a sample is continuously measured during heating. This test method can also clearly differentiate between polymer and filler and allows the polymer content of the film to be determined.

[0032] In one variant of the invention, calcium carbonate (CaCO3) is used as a filler, preferably with an average particle size of less than 6.5 pm. During the stretching process, the elastic polymeric components of the filled layer are stretched and voids are created in the layer. In one variant of the invention, the proportion of calcium carbonate is more than 40 wt. %, preferably more than 50 wt. %, in particular more than 60 wt. % and / or less than 90 wt. %, preferably less than 80 wt. % and in particular less than 70 wt. In addition to or as an alternative to calcium carbonate (CaCO3), a metal oxide component can be used as a filler. Alkaline earth oxides are particularly advantageous as metal oxide components, both as a filler to ensure the formation of pores in the layer and as an adhesive to ensure the adhesion of the printed image.Calcium oxide (CaO) has proven particularly advantageous, although the use of magnesium oxide is also conceivable.

[0033] Tale and / or titanium dioxide and / or dolomite have also proven particularly effective as fillers.

[0034] In a particularly advantageous variant of the invention, a cold sealant is applied to the film. This is preferably applied to the film using a rotary printing process. This allows the film to be sealed into a package in a packaging system at the manufacturer of, for example, ice cream, baked goods, and / or sweets.

[0035] Ideally, the cold sealant is applied directly to the film. This eliminates the need for additional intermediate and / or adhesive layers.

[0036] In a favorable variant of the invention, the cold seal compound is applied and arranged over a large area of ​​the film. "Overall" can mean that the entire film has a layer of cold seal compound. Furthermore, partial areas and / or geometric patterns made of cold seal compound can also be applied to the film, preferably depending on the packaging shape and design. The cold seal compound preferably consists of a natural latex base. Furthermore, synthetically produced cold seal compounds are also included within the scope of the invention.

[0037] The cold seal compound may also contain functional additives such as fillers, pigments, antiblocking agents, slip agents, and stabilizers. However, it is preferable to keep this surface as additive-free as possible to minimize any reduction in adhesion to cold seal self-adhesive compounds. Antiblocking agents are typically used in this layer to ensure excellent processability and roll formation. Examples of antiblocking agents include amorphous silica, cross-linked synthetic silicone particles, cross-linked polymethyl methacrylate particles, silicate-based antiblocking agents, and other commercially available antiblocking agents.

[0038] In an alternative variant of the invention, the film is formed into a package with another film. The second film is bonded to the second film after a print has been applied.

[0039] In an alternative variant of the invention, the film has at least one additional layer of EVOH and / or PA. This additional layer can be designed as an outer layer, to which the print adheres better. At the same time, this additional outer layer improves the heat resistance of the film. For this purpose, the additional layer 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.

[0040] 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 0.95 g / cm 3 , in particular less than 0.90 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 This is achieved in particular by the monoaxial stretching of the film and the formation of cavities in the filled layer.

[0041] Advantageously, the formation and inclusion of voids in a middle layer leads to a density of the film that is safely below 1.00 g / cm 3 lies.

[0042] In a particularly advantageous variant of the invention, the polyolefin is polyethylene. Polyethylene (PE) is a thermoplastic produced by chain polymerization of petrochemically produced ethylene. Polyethylene is semi-crystalline and non-polar.

[0043] Ideally, the polyolefin is formed exclusively as polyethylene. This means the film meets the requirements of the Plastics Pact, is based on a monomaterial construction, and is recyclable.

[0044] The film thickness was measured according to DIN 53370 and reported as an average value. After stretching in the monoaxial direction, the film has a thickness of less than 40 μm, preferably less than 35 μm, in particular less than 30 μm, and / or more than 5 μm, preferably more than 10 μm, in particular more than 15 μm. This distinguishes the film according to the invention significantly from previously known filled polyolefin films (FPO), whose thickness is usually more than 100 μm.

[0045] Ideally, the film is designed to be particularly thin and use minimal material. The film's construction thus complies with the design specifications of the Plastics Pact. Nevertheless, due to the special manufacturing process, the film exhibits outstanding properties that make it an ideal film, especially for food. In an advantageous variant of the invention, the film has a gas permeability of less than 500 cm³ 3 / m2 • d • bar, preferably less than 300 cm 3 / m 2 • d • bar, especially of less than 100 cm 3 / m 2 • d • bar according to DIN EN ISO 2556. DIN EN ISO 2556:2000 is the German version for determining the gas permeability of films and thin sheets under atmospheric pressure using the pressure gauge method (ISO 2556:1974).

[0046] Films and sheets up to 1 mm thick are tested using strip or shoulder specimens. According to ISO 527-3 and ASTM D 882, strips are the usual specimen shape. This specimen shape can be easily produced using a cutting press or a film cutter. Shoulder specimens are often used in quality control. In this case, a direct-measuring extensometer is required, which can record the specimen strains directly on the specimen. Typical test results include yield stress, yield strain, maximum stress, and nominal strain at break.

[0047] The tensile properties are determined according to DIN EN ISO 527. In the tensile test, a sample strip of a film is stretched at a constant speed specified in the test standard and the force F is recorded with the change in length AL of the measuring section Lo.

[0048] In film packaging applications, the linear-elastic and linear-viscoelastic loading ranges usually play a role. Films are frequently loaded precisely in these slight deformation ranges, for example, at 2% of the secant modulus. In an advantageous variant of the invention, the film has a tensile stiffness at 2% secant modulus according to DIN EN ISO 527-3 of more than 500 MPa, preferably more than 550 MPa, in particular more than 600 MPa.

[0049] Ideally, the film has a tensile strength in the machine direction according to DIN EN ISO 527-3 of more than 90 MPa, preferably more than 100 MPa, and especially more than 110 MPa. This makes the film particularly stiff and tough, which also allows for the application of a high-quality printed image.

[0050] Shrinkage of plastics refers to a change in the dimensional stability of test specimens at temperatures T > TG (amorphous) or T > Ts (semi-crystalline), which is caused by the recovery of molecular orientations and the relaxation of residual stresses. These orientations arise as a result of the processing process (extrusion, injection molding, or deep drawing) and are therefore dependent on processing parameters. These parameters include the temperature of the mold and the melt, the injection and holding pressure, the flow path length, and the cooling gradient of the film.

[0051] In a favorable variant of the invention, the film has a shrinkage according to DIN 55543-4 of less than 4%, preferably less than 3%, in particular less than 2%.

[0052] The dart drop test, also called falling dart impact test, drop hammer method or free falling dart method according to DIN EN ISO 7765-1, is a traditional method for assessing the impact resistance or toughness of a plastic film. A drop hammer with a variable weight and a diameter of 28 mm falls from a height of 0.66 m onto a wrinkle-free and firmly clamped film with a film thickness of 0.04 mm, under standard climate conditions. The weight of the drop hammer is determined which punctures the film in 50% of the drop tests. For example, the film has a dart drop according to DIN EN ISO 7765-1 of more than 95 g, preferably more than 115 g, in particular more than 135 g.

[0053] Optionally, the dynamic puncture energy according to DIN EN ISO 7765-2 is more than 10 J / mm, preferably more than 12 J / mm, in particular more than 14 J / mm.

[0054] In a favorable variant of the invention, the multi-layer structure of the film is symmetrical, whereby the printability of both outer layers can be realized.

[0055] The special properties of the film are achieved through the use and selection of special polymers.

[0056] Ideally, the outer, unfilled layer of the film comprises a blend of two polyethylenes of different densities, with the higher density polyethylene having a density of more than 0.94 g / cm 3 and the low-density polyethylene has a density of less than 0.94 g / cm 3 has.

[0057] Advantageously, the proportion of higher-density polyethylene in the mixture is more than 10 wt.%, preferably more than 20 wt.%, in particular more than 25 wt.% and / or less than 50 wt.%, preferably less than 40 wt.%, in particular less than 35 wt. The proportion of higher-density polyethylene imparts the film excellent rigidity and heat resistance.

[0058] In a particularly advantageous variant of the invention, the proportion of low-density polyethylene in the mixture is more than 50 wt.%, preferably more than 60 wt.%, in particular more than 65 wt.% and / or less than 90 wt.%, preferably less than 80 wt.%, in particular less than 75 wt.%. The proportion of low-density polyethylene ensures favorable toughness of the film.

[0059] Ideally, the higher density polyethylene is made of HDPE whose density is more than 0.942 g / cm 3, preferably more than 0.944 g / cm 3 and / or less than 0.96 g / cm 3 , preferably less than 0.95 g / cm 3 amounts.

[0060] Preferably, the low-density polyethylene is formed from an MDPE whose density is more than 0.91 g / cm 3 , preferably more than 0.92 g / cm 3 and / or less than 0.95 g / cm 3 , preferably less than 0.94 g / cm 3 amounts.

[0061] In variants of the inventions that have more than three layers, one or more intermediate layers are arranged between the filled layer and the unfilled, outermost layer. These intermediate layers are preferably unfilled and consist of an MDPE whose density is more than 0.91 g / cm 3 , preferably more than 0.92 g / cm 3 and / or less than 0.95 g / cm 3 , preferably less than 0.94 g / cm 3 amounts.

[0062] The flow behavior of polyolefins is described using the melt index Ml (melt index) according to ASTM 1238, usually 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 has a melt index M1 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 index 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.

[0063] The HDPE preferably has a medium molecular weight and a particularly narrow molecular weight distribution, which leads to good bubble stability and processability. Furthermore, the HDPE layers exhibit excellent tensile strength and good elongation at break with a low tendency to fibrillation.

[0064] The MDPE advantageously has a melt index M1 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. Furthermore, the melt index 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 layers with MDPE and the film achieve high toughness and, at the same time, high stiffness values.

[0065] In a particularly preferred variant, the film comprises more than one intermediate layer, preferably more than two intermediate layers, all made of the same MDPE. This special multi-layer construction gives the film particularly high toughness and rigidity, while simultaneously preventing the formation of fibrils.

[0066] Ideally, the filled layer comprises, in addition to the filler, a mixture of different polymers, wherein the mixture comprises a proportion of LDPE, a proportion of MDPE and a proportion of HDPE.

[0067] In a particularly advantageous variant of the invention, the proportion of LDPE in the mixture of the filled layer is more than 6 wt.%, preferably more than 10 wt.%, in particular more than 14 wt.% and / or less than

[0068] 24 wt.%, preferably less than 20 wt.%, in particular less than

[0069] 16 wt%.

[0070] Advantageously, the proportion of MDPE in the mixture of the filled layer is more than 7 wt.%, preferably more than 12 wt.%, in particular more than 17 wt.% and / or less than 30 wt.%, preferably less than

[0071] 25% by weight, in particular less than 20% by weight.

[0072] Preferably, the proportion of HDPE in the mixture of the filled layer is more than 4 wt.%, preferably more than 7 wt.%, in particular more than 10 wt.% and / or less than 20 wt.%, preferably less than

[0073] 17 wt%, in particular less than 14 wt%.

[0074] In principle, five-layer and seven-layer films are also included in the scope of the invention, whereby the mechanical properties can be improved with an increasing number of layers.

[0075] Preferably, the print is applied directly to an outer layer of the film. The print or overprint can be applied on the side facing away from the packaged product or as a counterprint between the film and, if applicable, another film. Furthermore, the print can be implemented as a printed motif. In the film sector, the term "print motif" refers to the thematic design element of an overprint. If appropriate, manufacturer-identifying print motifs can also be included in the overprint.

[0076] 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.

[0077] The special selection of polymers and the three- to nine-layer design result in a particularly thin film that nevertheless exhibits impressive mechanical properties, even in a monomaterial construction. Despite the thin design, the rigidity and toughness, achieved in particular by the polyethylene blend in at least one outer layer, result in excellent printability. The filled layer with cavities, in particular, results in an opaque film that is ideal for printing.

[0078] According to the invention, the method for producing packaging comprises several steps. First, the polymer components are mixed, which is then extruded into a film with at least two layers. The polymer mixtures differ with regard to the filled and unfilled layers of the film, with the polymer mixture of the filled layer comprising an inorganic filler to create cavities. Advantageously, the film is stretched monoaxially in the machine direction, thereby achieving the favorable properties of the PE film. This includes, among other things, advantageous opacity, so that the film can be directly printed. Preferably, a cold sealing compound is applied to the inside of the film after and / or before and / or simultaneously with the printing process using a rotary roll process.For this purpose, the cold sealing compound can preferably be applied flatly and directly onto the outer layer of the film.

[0079] The film is produced by monoaxial stretching with machine direction orientation (MDO), where the polymer film is heated to a temperature slightly below its melting point and stretched in a specific orientation. Stretching can also be performed directly after extrusion, when the film is still at a temperature slightly below its melting point.

[0080] MDO stretched and oriented film enables the packaging of food and other items based on a particularly thin film and a uniform, single material structure. MDO stretching achieves properties in PE film that were previously only known from multi-material constructions or from PP and PET films.

[0081] In an advantageous variant of the invention, the film is stretched by a factor of more than three, preferably by a factor of more than four, in particular by a factor of more than five. This gives the film advantageous stiffness and favorable opacity.

[0082] In a particularly advantageous variant, the opaque, printed film is bonded to another film to form a packaging, particularly a packaging laminate. In principle, all common and known bonding methods are suitable for this. The additional film is preferably also based on a monomaterial construction made of polyethylene.

[0083] In a particularly advantageous variant of the invention, the further film is a nine-layer film, preferably based on MDPE, which is also monoaxially stretched in the machine direction.

[0084] In a favorable embodiment of the further film, at least one outer layer has a higher density than the at least one inner layer. The outer layer comprises a mixture of at least two polyethylenes of different densities, with the higher-density polyethylene having a density of more than 0.94 g / cm 3 and the low-density polyethylene has a density of less than 0.94 g / cm 3 on.

[0085] Ideally, the density of the higher density polyethylene is a factor greater than the lower density polyethylene, 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.

[0086] Preferably, the inner layer is formed from an MDPE whose density is more than 0.91 g / cm 3 , preferably more than 0.92 g / cm 3and / or less than 0.95 g / cm 3 , preferably less than 0.94 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.

[0087] In a particularly preferred variant, the polyethylene film comprises more than one inner layer, preferably more than two inner layers, in particular more than four inner layers, all formed from the same MDPE. This special multi-layer construction provides the polyethylene film with particularly high toughness and rigidity, while simultaneously preventing the formation of fibrils in a particularly advantageous manner.

[0088] Ideally, the higher density polyethylene of the further film in the outer layer is made of a HDPE whose density is more than 0.942 g / cm 3, preferably more than 0.944 g / cm 3 and / or less than 0.96 g / cm 3 , preferably less than 0.95 g / cm 3 and / or whose melt flow rate (at 190 °C at 2.16 kg) according to ASTM D 1238 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.

[0089] Advantageously, the low-density polyethylene of the outer layer of the further film is formed from an MDPE whose density is more than 0.91 g / cm 3 , preferably more than 0.92 g / cm 3 and / or less than 0.95 g / cm 3 , preferably less than 0.94 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.

[0090] In a particularly simple design variant of the additional film, the film comprises three layers. The inner layer is preferably made of MDPE, while the two outer layers are made of a polymer blend of HDPE and MDPE.

[0091] In a particularly advantageous variant of the invention, the further film comprises a nine-layer structure. Preferably, three equally thin inner layers made of MDPE form the core of the further film, each surrounded by an inner intermediate layer. Ideally, the inner intermediate layers are also made of MDPE and are approximately twice as thick as the inner layers. An outer intermediate layer is arranged between each inner intermediate layer and the outer layer. The outer intermediate layer is somewhat thicker than the inner intermediate layer and preferably consists of a mixture of high- and low-density polyethylene.The outer layer has a thickness that is slightly greater than the thickness of the outer intermediate layer and also consists of a mixture of high and low density polyethylene, with the outer layer additionally containing a small proportion of additives.

[0092] In a particularly advantageous variant of the additional film, the thickness of the layers increases from the inner layer to the outer layer. This applies to the three-layer to the nine-layer additional film. This version of the additional film achieves particularly advantageous mechanical properties and thus creates a film that can be printed with high quality.

[0093] Furthermore, the further film is ideally 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.

[0094] Advantageously, the further film 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.

[0095] The film according to the invention is used as a recyclable and single-material cold-seal packaging for food. The film offers the advantages of a mono-material construction, while achieving and exceeding many of the features of multi-component constructions and meeting the requirements of the European Union's Plastics Pact.

[0096] According to the invention, the film is combined with another film to form a package. The combined films are used as recyclable, single-material packaging for food.

[0097] 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.

[0098] This shows

[0099] Fig. 1 is a schematic representation of the film according to the invention with a cold sealing compound,

[0100] Fig. 2 a schematic representation of the film with additional layer,

[0101] Fig. 3 is a schematic representation of the packaging according to the invention with a cold sealing compound,

[0102] Fig. 4 shows a further variant of the packaging according to the invention.

[0103] Fig. 1 shows a schematic representation of the packaging 13 according to the invention in the embodiment of film 1 with a cold sealant 2 and the print 4. In the illustrated embodiment, film 1 has a nine-layer structure. Layer 6 is the filled layer, with the CaCO3 content being approximately 55 wt. Furthermore, layer 6 has a LDPE content of approximately 15 wt.%, a MDPE content of approximately 18 wt.%, and a HDPE content of approximately 12 wt.%.

[0104] Layers 5 form the outer layers of film 1, with layers 5 containing no fillers. In layer 5, the MDPE content is approximately 70 wt.% and the HDPE content is 30 wt.%. The HDPE is made, for example, from Hostalen ACP 7740 F3, whose 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.

[0105] Three additional thin layers 10 are arranged between the filled layer 6 and the unfilled layers 5. The layer 10 is made entirely of an MDPE, for example a Borealis Borshape FX1002, 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.

[0106] First example:

[0107] Film 1 has a thickness of 119 pm after blow extrusion. After monoaxial stretching by a factor of 4.82, the thickness of film 1 is 24.7 pm, with a density of 0.92 g / cm 3 .

[0108] Second example:

[0109] Film 1 has a thickness of 147 pm after blow extrusion. After monoaxial stretching by a factor of 5.74, the thickness of film 1 is 40 pm, with a density of 0.86 g / cm 3 .

[0110] Film 1 exhibits a tensile stiffness of more than 632 MPa at a 2% secant modulus and a tensile strength in the machine direction according to DIN EN ISO 527-3 of more than 119.3 MPa. Furthermore, the shrinkage of film 1 according to DIN 55543-4 is less than 2.1%, while the opacity according to DIN EN ISO 2813 is more than 95%. Film 1 exhibits a dart drop of 135.4 g according to DIN EN ISO 7765-1.

[0111] Fig. 2 shows a schematic representation of the packaging 13 according to the invention in the form of film 1 with an additional layer 12. The film

[0112] I essentially corresponds to the embodiments of Fig. 1 , wherein in this embodiment an additional layer 12 of EVOH is arranged between the print 4 and the layer 5.

[0113] Fig. 3 shows a schematic representation of the packaging according to the invention

[0114] II with a cold sealing compound 2. The packaging 11 is formed from the film 1 and the further film 3.

[0115] Between the additional film 3 and the film 1, a print 4 is arranged, which is printed onto the opaque film 1 before bonding. The print 4 serves to label the food to be packaged, as well as for visual recognition and to support the brand image of the food brand.

[0116] In this embodiment, the additional film 3 is constructed with nine layers in a symmetrical structure. The five innermost layers 7 and 9 are made entirely of MDPE, for example, Borealis Borshape FX1002, with the three innermost layers 9 being significantly thinner than the two surrounding layers 7.

[0117] Each of the two outer layers 8 of the further film 3 contains a proportion of HDPE in addition to MDPE. In the illustrated embodiment, the proportion of HDPE is 85 wt.% and is made, for example, from a Hostalen ACP 7740 F3.

[0118] First example

[0119] The nine-layer, further film 3 has a thickness of 139 pm after blow extrusion. After monoaxial stretching by a factor of 5.95, the thickness of further film 3 is 25 pm, with a density of 0.905 g / cm 3 .

[0120] Second example:

[0121] Film 1 has a thickness of 147 pm after blow extrusion. After monoaxial stretching by a factor of 5.74, the thickness of film 1 is 40 pm, with a density of 0.86 g / cm 3 .

[0122] In the embodiment shown in Fig. 3, film 1 has a three-layer structure. Layer 6 is the filled layer, with the CaCO3 content being approximately 55 wt. Furthermore, layer 6 has a LDPE content of approximately 15 wt., a MDPE content of approximately 18 wt., and a HDPE content of approximately 12 wt.

[0123] The filled layer 6 is surrounded by a layer 5, with the unfilled layer 5 containing no fillers. In layer 5, the proportion of MDPE is approximately 70 wt.% and the proportion of HDPE is 30 wt.%.

[0124] Film 1 has a thickness of 140 pm after blow extrusion. After monoaxial stretching by a factor of 4.82, the thickness of film 1 is 29 pm, with a density of 0.87 g / cm 3 .

[0125] The embodiment of the packaging 11 shown in Fig. 4 essentially corresponds to the embodiment in Fig. 3. Only the film 1 has a nine-layer structure as already described in detail in Fig. 1.

Claims

Claims: Recyclable, cold-sealable packaging (11, 13) comprising at least one first film (1), a cold-seal compound (2), and a print (4), wherein the film (1) is made of a largely pure polyolefin, is monoaxially stretched in the machine direction, and has at least two layers (5, 6), characterized in that at least one layer (6) comprises an inorganic filler for creating cavities in the layer. Packaging according to claim 1, characterized in that the cold-seal compound (2) is arranged directly on the film (1). Packaging according to claim 1 or 2, characterized in that the cold-seal compound (2) is arranged planarly on the film (1). Packaging according to any one of claims 1 to 3, characterized in that the filled layer (6) is formed as an inner layer, wherein the inner layer is surrounded by two unfilled layers (5).

5. Packaging according to one of claims 1 to 4, characterized in that the density of the film (1) is less than 0.99 g / cm³ 3 , preferably less than 0.95 g / cm³ 3 , especially less than 0.90 g / cm³ 3 is and / or more than 0.60 g / cm² 3 , preferably more than 0.70 g / cm³ 3 , especially more than 0.80 g / cm² 3 amounts.

6. Packaging according to any one of claims 1 to 5, characterized in that the polyolefin is polyethylene.

7. Packaging according to any one of claims 1 to 6, characterized in that the filler is CaCOs, wherein the filler has a particle size of less than 6.5 pm.

8. Packaging according to one of claims 1 to 7, characterized in that the proportion of filler in layer (6) is more than 5 wt.%, preferably more than 10 wt.%, in particular more than 15 wt.% and / or less than 60 wt.%, preferably less than 50 wt.%, in particular less than 40 wt.%. Packaging according to any one of claims 1 to 8, characterized in that the film (1) has a thickness of less than 40 pm, preferably less than 35 pm, in particular less than 30 pm, and / or more than 5 pm, preferably more than 10 pm, in particular more than 15 pm. Packaging according to any one of claims 1 to 9, characterized in that the film (1) has a gas permeability of less than 500 cm⁻¹. 3 / m 2 d bar, preferably of less than 300 cm 3 / m 2 d bar, especially of less than 100 cm 3 / m 2Packaging according to any one of claims 1 to 10, characterized in that the film (1) has an opacity according to DIN 53416 of more than 80%, preferably more than 90%, and in particular more than 95%. Packaging according to any one of claims 1 to 11, characterized in that the film (1) has a tensile stiffness at 2% secant modulus according to DIN EN ISO 527-3 of more than 500 MPa, preferably more than 550 MPa, and in particular more than 600 MPa. Packaging according to any one of claims 1 to 12, characterized in that the film (1) has a tensile strength in the machine direction according to DIN EN ISO 527-3 of more than 90 MPa, preferably more than 100 MPa, and in particular more than 110 MPa. Packaging according to any one of claims 1 to 13, characterized in that the film (1) has a shrinkage according to DIN 55543-4 of less than 4%, preferably less than 3%, and in particular less than 2%. Packaging according to any one of claims 1 to 14, characterized in that the film (1) comprises a layer (12) of ethylene-vinyl alcohol copolymer (EVOH) or polyamide (PA). Packaging according to any one of claims 1 to 15, characterized in that the packaging (11) comprises at least one further film (3), wherein the film (3) comprises at least two layers of polyethylene of different densities and is stretched in the machine direction.

17. Packaging according to one of claims 1 to 16, characterized in that the film (1 ) has a dart drop according to DIN EN ISO 7765-1 of more than 95 g, preferably of more than 115 g, in particular of more than 135 g.

18. Method for producing a package (11, 13) comprising the following steps: Production of various compositions, Extrusion to form a film (1) with at least two layers (5, 6), Printing the film (1), characterized in that the film (1 ) is stretched monoaxially in the machine direction.

19. Method according to claim 18, characterized in that the extrusion is carried out as bubble extrusion.

20. Method according to claim 18 or 19, characterized in that the film (1) is stretched by more than a factor of 3, preferably more than a factor of 4, in particular more than a factor of 5.

21. A method according to any one of claims 18 to 20, characterized in that the film (1) is combined with at least one further film (3) to form a package (11).

22. A method according to any one of claims 18 to 21, characterized in that a cold-sealable compound (2) is applied to the film (1).

23. Use of a film (1) according to one of claims 1 to 17 as a recyclable, single-material cold-seal packaging (13).

24. Use of a film (1) as a laminate with a further film (3) according to any one of claims 1 to 17 as recyclable, single-material packaging (11)-

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