Silage film

Abstract

The invention relates to a silage film with a total thickness between 75 µm and 150 µm, comprising at least one outer and at least one inner layer, a central layer composed of a soft polyethylene (PE), selected from linear low-density polyethylene (LLDPE) or low-density polyethylene (LDPE), at least one functional layer arranged on either side of the central layer and at least one intermediate layer positioned between each functional layer and the outer or the inner layer. At least one functional layer is composed of a special polyethylene that replaces conventional barrier layers. The silage film is entirely free of any barrier layers, including polyamide (PA) or ethylene vinyl alcohol (EVOH).

Description

[0001] RKW V684

[0002] Silo film

[0003] Description

[0004] The invention relates to a silage film with a total thickness between 75 pm and 150 pm, comprising at least one outer and at least one inner layer, a central layer composed of a soft polyethylene (PE), selected from linear low-density polyethylene (LLDPE) or low-density polyethylene (LDPE), at least one functional layer arranged on either side of the central layer, at least one intermediate layer positioned between each functional layer and the outer or the inner layer.

[0005] Such multilayer silage films with barrier configurations are used in agricultural applications. An important application is silage films. Silage film technology is an efficient, flexible, and environmentally friendly method for preserving and storing all types of feed in specially designed film bags. Originally developed for the silaging of green material, today a wide variety of substrates can be stored in silage films. Silage films are also utilized for composting organic materials. For instance, pressed pulp, as well as corn and grass silage, are now stored in silage films.

[0006] Sealing against oxygen is of crucial importance for ensiling. Traditionally, stable polyethylene-based films have been used for silage films or silage tubs. However, the use of these conventional films has repeatedly led to the formation of mold due to the penetration of oxygen.

[0007] Conventional films for silage tubes based on typically conventional polyolefins would have to be very thick to ensure sufficient impermeability to oxygen and would therefore be heavy and relatively expensive to produce.

[0008] The use of EVOH as a barrier material leads to excellent barrier results, but EVOH cannot provide sufficient mechanical properties for use in silage tubes. RKW V684

[0009] 2

[0010] For this reason, films with special barrier arrangements were developed for silage tubes. These barrier arrangements are polymers that have a particularly high impermeability to gases, especially oxygen.

[0011] DE 698 17 012 T2 describes a multi-layer film for agricultural silage products. The film has a layer made of a polyamide that acts as an oxygen barrier. The film product can consist of two or more layers, for example co-extruded layers, of which at least one layer or possibly even several layers consist of an insulating plastic layer. In the case of a multilayer film with at least two insulating layers, these insulating layers may consist of the same plastic material or of different plastic materials, all of which are airtight.

[0012] DE 10 2009 052 948 B4 describes a covering system for silage with an underlay film made of a polyamide and a silage film made of a polyethylene.

[0013] Polyamide has excellent puncture resistance, but the tear resistance is often not sufficient for the challenging use as a silage film in agriculture.

[0014] DE 10 2017 107 060 A1 discloses a method for increasing the tear resistance of a multilayer film. The multilayer film has at least one barrier arrangement which comprises a total thickness for reducing gas permeability. According to the invention, the barrier arrangement is divided into at least two layers to increase the tear resistance.

[0015] As part of the European Green Deal and the Circular Economy Action Plan, the EU has formulated the target that all packaging placed on the market in the EU should be either reusable or fully recyclable by 2030.

[0016] By 2025, at least 65 % of all packaging waste is to be recycled, with a quota of at least 50 % to be achieved for plastics, of which films are often made. By 2030, this figure is to rise to 55 % for plastic based films. RKW V684

[0017] 3

[0018] Recycling PE plastic films containing EVOH can be problematic because EVOH has barrier properties that complicate processing. EVOH is water-soluble and difficult to separate from polyethylene, which negatively affects the quality of the recycling. Additionally, the different melting points and chemical properties of these materials can result in poor mixing during recycling. The outcome is often lower quality recyclates that do not meet the requirements for new applications.

[0019] The problem with recycling polyethylene films that contain PA (polyamide) is primarily due to the differences in their chemical and physical properties. PA has a higher melting point and different thermal behavior compared to polyethylene, which can complicate the recycling process. During recycling, these materials may not blend well, leading to a lower-quality recycled product. Additionally, the presence of PA can create challenges in achieving the desired properties for the recycled material, making it less suitable for new applications.

[0020] PA or EVOH can cause nozzle blockages and negatively affect bubble stability during the blow extrusion of polyethylene films. This occurs because both materials have different thermal and viscoelastic properties. Polyamide has a higher melting point and a different flow behavior, which can prevent it from mixing optimally with polyethylene during the extrusion process. This can lead to deposits in the nozzles, reducing the flow rate and resulting in uneven extrusion.

[0021] EVOH, which also has a high melting point, can create similar issues. It tends to decompose at higher temperatures, leading to impurities and deposits forming in the nozzles. Additionally, the combination of EVOH and polyethylene can compromise bubble stability, as the differing material properties may result in an unstable bubble contour. This can increase the risk of bubble breaks and negatively impact the quality of the films. Therefore, careful control of processing temperatures and conditions is essential to minimize these issues and ensure consistent product quality. RKW V684

[0022] 4

[0023] The task of the present invention is to make silage film in order to fulfil the future requirements of the Plastics Pact 2025. In addition, the film should be designed to be fully recyclable without any processing challenge. The silage film should also be suitable for packaging and storing grain, silage, warm or wet industrial products. In addition, the silage film should be able to exhibit the mechanical properties achieved to date. In addition, the film should be able to be produced very inexpensively in order to be competitive in the agriculture sector, which is under price pressure.

[0024] According to the invention, this task is ensured by a silage film, a method and a use according to the subsidiary main claims. Preferred variants can be found in the sub-claims, the description, the embodiment example and the drawing.

[0025] According to the invention, at least one functional layer is composed of a special polyethylene that replaces conventional barrier layers. The Silage film is entirely free of any barrier layers, including polyamide (PA) or ethylene vinyl alcohol (EVOH).

[0026] For example, the silage film has an oxygen transmission rate of less than 250 cm3 / m2 / 24h at 23 °C and 75 % relative humidity, measured according to EN 13207.

[0027] In one variant of the invention, the at least one intermediate layer comprises a masterbatch, containing particles that reduce oxygen permeability.

[0028] For example, at least one of the functional layers comprises a masterbatch, containing particles that reduce oxygen permeability.

[0029] In one variant of the invention, the masterbatch contains at least 30 wt.-% particles that create a tortuous path for gas and moisture molecules, thereby RKW V684

[0030] 5 significantly enhancing the barrier properties of the functional layers to achieve an oxygen permeability of the film of less than 250 cm3 / m2d bar according to EN 13207.

[0031] At same time, the film has a water vapour permeability of less than 20 g / m2in 24 h according to ASTM D6701-01.

[0032] The water vapor permeability of dry or moisture-sensitive goods is determined in accordance with DIN 53116 or ASTM D6701-01 using a gravimetric measurement method. A test container filled with a desiccant is sealed with a sample of foil and exposed to a defined test climate. The amount of water permeating through the sample is determined by weighing. A quantity of water in a range of 1 - 200 g / (m2■ d) can be detected. The detection limit is also dependent on the composition and thickness of the sample.

[0033] For example, the film has a water vapour permeability of less than 10 g / m2in 24 h according to ASTM D6701-01.

[0034] In a variant of the invention, the silage film has a water vapor permeability of less than 8 g / m2, preferably less than 6 g / m2, in particular less than 4 g / m2in 24 h according to ASTM D6701-01. This protects grain, silage, warm or wet industrial products that are stored in silage films, even for longer periods of time.

[0035] In one variant of the invention, only the functional layers comprising a specific polyethylene material containing at least 5 wt.-% of a masterbatch additive.

[0036] In another variant of the invention, only the intermediate layers comprising a specific polyethylene material containing at least 5 wt.-% of a masterbatch additive. RKW V684

[0037] 6

[0038] In a third variant of the invention, the functional layers and the intermediate layers comprising a specific polyethylene material containing at least 5 wt.-% of a masterbatch additive.

[0039] For example, the functional layers and the intermediate layers comprising the same content of a masterbatch.

[0040] In another variant of the invention, the functional layers and the intermediate layers comprising different contents of the masterbatch.

[0041] In a different variant of the invention, only the intermediate layers containing at least 5 wt.-% of a masterbatch additive.

[0042] For example, at least one of the functional layers and / or one of the intermediate layers comprising a specific polyethylene material containing of more than 7.5 wt.-%, preferably of more than 10 wt.-%, in particular of more than 12,5 wt.- % and less of 20 wt.-%, preferably of less than 18,5 wt.-%, in particular of less than 16 wt.-% of a masterbatch additive.

[0043] In one variant of the invention, the intermediate layer consists of less than 20 wt.- % of the masterbatch, wherein the masterbatch contains particles that create a tortuous path for gas and moisture molecules, thereby enhancing the barrier properties of the film.

[0044] In order for a film to fulfil its task, it must have a certain oxygen impermeability. This is the only way to ensure the adequately protected storage of sensitive grain, silage, warm or wet industrial products.

[0045] The oxygen permeability of the film is determined in accordance with EN 13207 (“Plastics - Packaging - Films and Film Laminates - Determination of Oxygen Transmission Rate”). The oxygen transmission rate (OTR) is measured under RKW V684

[0046] 7 defined climatic conditions. Typically, the measurement is carried out at 23 °C and 0 % relative humidity. In the case of silage films, however, the test is performed under practical conditions with 75 % relative humidity, since the silage material enclosed within the film is warm and moist, and these climatic conditions realistically reflect the actual environment. The test procedure is based on the permeation of oxygen through a film specimen separating a chamber into an oxygen-containing and an oxygen-free side. The oxygen flow is continuously recorded until a steady state is reached. The result is expressed in cm3 / m2d (cubic centimeters per square meter per day) and serves to quantitatively assess the barrier properties of the film against oxygen.

[0047] For example, the film has an oxygen permeability of less than 200 cm3 / m2d bar, preferably less than 150 cm3 / m2d bar, in particular less than 50 cm3 / m2d bar at 23°C and 75 % relative humidity in accordance with EN 13207.

[0048] The oxygen transmission rate (OTR) of plastic films is determined in accordance with ASTM D3985 (“Standard Test Method for Oxygen Gas Transmission Rate Through Plastic Film and Sheeting Using a Coulometric Sensor”). In this method, a film specimen separates two chambers, one containing oxygen and the other being swept with nitrogen. Oxygen permeating through the specimen is quantitatively measured by a coulometric sensor until steady-state transmission is reached. The result is expressed as cm3 / m2day under specified temperature and humidity conditions, providing a reliable measure of the barrier performance of films against oxygen.

[0049] In a different variant of the invention, the film has an oxygen permeability of less than 150 cm3 / m2d bar, preferably less than 100 cm3 / m2d bar, in particular less than 50 cm3 / m2d bar at 23°C and 50 % relative humidity in accordance with ASTM D3985. RKW V684

[0050] 8

[0051] The PA-free and EVOH-free design of the film can be achieved, for example, by selecting a special polyethylene for the functional layer in combination with a very favourable masterbatch. Only the PA-free and EVOH-free design of the silage film can achieve genuine recyclability, in which high bubble stability can also be realised during the extrusion process when using the recyclates from the silage film.

[0052] The masterbatch can consists of a polyethylene carrier material and an active ingredient preferably a nanoclay, which is composed of layered silicates, such as montmorillonite.

[0053] The physical effect achieved when the beneficial masterbatch is incorporated into the polyethylene functional layer is mainly based on the creation of a tortuous path for the molecules of water vapour and gases.

[0054] Nanoclay is a special form of clay that consists of tiny particles on a nanoscale. These fine clay minerals, which either occur naturally or are produced synthetically, are characterised by a special layered structure. They usually consist of layered silicates in which ultra-thin layers of silicon and aluminium silicates alternate. Due to this structure, nanoclays offer an extremely large surface area, which accounts for their special properties.

[0055] One of the most common forms of nanoclay is montmorillonite, which consists of finely structured layered silicates, but kaolinite is also a common variant. Nanoclays have outstanding mechanical properties that make them a valuable material reinforcer. Thanks to their nanostructure, they can significantly improve the mechanical strength, heat resistance and stability of plastics. They also act very favourably as barriers against gases and liquids by reducing their permeability. RKW

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[0057] 9

[0058] The nanoclay particles act as physical barriers for gas or water molecules that want to diffuse through the polymer. Without the nanoclay particles, gas molecules can pass through the amorphous areas of the polyethylene relatively easily. However, when nanoclay is introduced into the polyethylene layer, the gas molecules have to travel a much longer, complicated path around these particles, which significantly slows down the diffusion process

[0059] For example, the size of the particles ranges from 1 to 100 nm. These particles have an extremely high surface area and are often a few nanometres to micrometres in size. Nanoclay is evenly distributed in the functional or intermediate polyethylene layer through the manufacturing process.

[0060] For example, the masterbatch has a density of more than 0.94 g / cm3and less than 1.05 g / cm3. In the masterbatch, these nanoclays and layered silicates are processed in such a way that they are optimally dispersed in the functional or intermediate polyethylene layer. The nanoclay particles are able to change the physical properties of the material without affecting the flexibility or processability of the film.

[0061] In one special variant of the invention, the masterbatch has a density of more than 0.94 g / cm3and less than 0.96 g / cm3.

[0062] The replacement of traditional barrier materials such as EVOH and PA is made possible not only by the masterbatch but also by the specially engineered polyethylene. This advanced polyethylene structure enhances barrier properties, providing the necessary strength and resistance to protect contents effectively, thereby enabling the film to perform without additional barrier layers.

[0063] In one variant of the invention, the polyethylene (PE) of the functional layer has a density of more than 0.925 g / cm3and less than 0.930 g / cm3. RKW V684

[0064] 10

[0065] The molecular weight distribution (MWD) describes the distribution of molecular weights or chain lengths of molecules in a sample, especially in polymers. Since polymers consist of chains with varying lengths, they do not have a uniform molecular mass, but a range of masses. The molecular weight distribution indicates how these masses are distributed in the sample. A measure of the width of the molecular weight distribution, defined as the polydispersity index (PDI).

[0066] A PDI value of 1 means that all molecules have the same mass (monodisperse), while larger values indicate a broad distribution (polydisperse). The molecular weight distribution influences the properties of polymers, such as viscosity, melting point, mechanical strength and solubility. Polymers with a narrow distribution (small PDI) often show a more uniform behaviour, while polymers with a broad distribution (high PDI) can have more complex properties. Methods such as gel permeation chromatography (GPC) or light scattering are used to measure the molecular weight distribution in polymers.

[0067] In one variant of the invention, the PE of the functional layer has a molecular weight distribution (PDI) according to ISO 16014 of less than 2.

[0068] Short-chain branching (SCB) refers to the presence of short side chains in the main chain of a polymer, typically in polyolefins such as polyethylene or polypropylene. These side chains often consist of a few carbon atoms (e.g. methyl, ethyl or butyl groups) and are formed by incomplete polymerization processes, such as those that occur in the production of low-density polyethylene (LDPE) or certain copolymers.

[0069] SCB reduces the density of the polymer as the branches prevent the molecular chains from packing tightly together. The short branches reduce the ability of the polymer to form ordered, crystalline structures, which can lead to a semicrystalline or amorphous material. The presence of SCB affects the flexibility, RKW V684

[0070] 11 strength and toughness of the polymer. Polymers with more SCB usually have a lower melting point.

[0071] For example, the PE of the functional layer has a short-chain branching (SCB) of 5 - 20 SCB per 1000 carbon atoms.

[0072] Elongation at Break is a mechanical parameter that describes the ability of a material to stretch before it tears under load. It is specified as a percentage change in length in relation to the original length of the material. Materials with a high elongation at break can stretch considerably without breaking, which indicates high ductility or elasticity.

[0073] In one variant of the invention, the PE of the functional layer has an elongation at break according to ISO 527-1 of more than 400 %, preferably more than 550 %, in particular more than 700 %.

[0074] All these special properties of the PE of the PE-based functional layer realise a functional layer that comes very close to the mechanical properties and barrier properties of a polyamide, whereby an otherwise conventional barrier layer can be replaced by this special PE-based functional layer.

[0075] In addition, the embodiment of the silage film according to the invention is the first to realise a variant that is also considered recyclable according to the new requirements of the European Union and which also proves itself in the practical implementation of recycling by completely replacing the polyamide with advantageous mechanical properties and barrier properties.

[0076] In one variant of the invention, the thickness of the functional layer is more than 10 pm and less than 25 pm. RKW V684

[0077] 12

[0078] For example, the at least one functional layer is directly adjacent to the central layer.

[0079] The central layer, for example, is made of a very soft polyethylene (PE).

[0080] The very soft polyethylene can be made from LDPE or mLLDPE or uLLDPE or a mixture.

[0081] Low-density polyethylene (LDPE) is a flexible, lightweight polymer known for its high ductility and resistance to impact. Its branched molecular structure results in a less crystalline, more amorphous material, making LDPE softer and more transparent compared to other types of polyethylene. These properties provide LDPE with excellent moisture resistance and ease of processing, making it ideal for applications such as film and packaging where flexibility and durability are required.

[0082] Linear low-density polyethylene (LLDPE) is a tough, flexible polymer characterized by its linear structure with minimal branching, giving it higher tensile strength and puncture resistance than LDPE. This structure makes LLDPE more resilient, while still allowing for flexibility and stretch. It also has improved impact resistance and is well-suited for film applications, particularly in packaging, where durability and strength are critical. Additionally, LLDPE can be processed efficiently in a variety of methods, including extrusion and molding, making it versatile for numerous industrial applications.

[0083] Metallocene linear low-density polyethylene (mLLDPE) is a specialized form of LLDPE produced using metallocene catalysts, resulting in a highly uniform polymer structure with controlled molecular weight distribution. This unique structure provides exceptional clarity, toughness, and flexibility, with enhanced puncture and tear resistance compared to standard LLDPE. Additionally, it allows RKW V684

[0084] 13 for thinner film production without sacrificing durability, contributing to material efficiency and cost-effectiveness.

[0085] Ultra-linear low-density polyethylene (uLLDPE) is an advanced variant of LLDPE known for its ultra-linear structure, achieved through specialized catalyst technology. This structure results in minimal branching, enhancing the material’s mechanical properties such as tensile strength, puncture resistance, and elasticity. uLLDPE combines exceptional durability with superior clarity and flexibility, making it ideal for high-performance films in packaging and industrial applications that demand both strength and resilience. Additionally, its ultra-linear nature allows for the production of thinner films while maintaining optimal barrier properties, contributing to sustainable material usage and improved product performance.

[0086] In one variant of the invention, the uLLDPE of the central layer has a density of more than 0.880 g / cm3, preferably more than 0.906 g / cm3and less than 0.912 g / cm3, preferably less than 0.910 g / cm3.

[0087] For example, the thickness of the central layer is more than 4 pm and less than 15 pm. This means that the central layer is particularly thin and saves material, while still having excellent soft properties.

[0088] The flow behavior of polyolefins is described using the melt flow rate respectively the MFI according to ISO 1133-1 , usually at a temperature of 190 °C for polyethylene at a load of 2.16 kg, 5 kg or 21.6 kg. A higher melt flow 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 a high output of the extrusion system. On the other hand, polymers with a high molecular weight, i.e. a low melt index, are advantageous in terms of mechanical stability, in particular tensile strength or toughness. RKW V684

[0089] 14

[0090] In one variant of the invention, the very soft polyethylene (PE) has MFI (at 190 °C at 2.16 kg) according to ISO 1133-1 is more than 1.0 g / 10 min and is less than 4.0 g / 10 min.

[0091] For example, the intermediate layer has a proportion of mLLDPE. Exemplarily, the amount of mLLDPE in the intermediate layer is more than 55 % by weight and / or less than 85 % by weight.

[0092] In one variant of the invention, the amount of mLLDPE in the intermediate layer is more than 70 % by weight and / or less than 80 % by weight.

[0093] For example, the intermediate layer has a proportion of mLLDPE which density according to ISO 1183-1 is more than 0.920 g / cm3and is less than 0.924 g / cm3, and which Ml (at 190 °C at 2.16 kg) according to ISO 1133-1 is more than 0.1 g / 10 min and is less than 0.5 g / 10 min.

[0094] The mLLDPE used in the intermediate layer is characterized by a linear molecular structure with relatively few but large side chains. This unique configuration influences its physical properties, notably allowing the material to exhibit shearthinning behavior. As a shear-thinning polymer, its viscosity decreases under applied stress or force, facilitating smoother flow under pressure. This combination of structural linearity, limited side branching, and shear-thinning capacity enhances the material’s processability, making it suitable for applications where controlled flow and strength are essential.

[0095] For example, the intermediate layer has a proportion of LDPE. Exemplarily, the amount of LDPE in the intermediate layer is more than 5 % by weight and / or less than 45 % by weight.

[0096] In one variant of the invention, the amount of LDPE in the intermediate layer is more than 15 % by weight and / or less than 30 % by weight. RKW V684

[0097] 15

[0098] For example, the intermediate layer has a proportion of LDPE which density according to ISO 1183-1 is more than 0.919 g / cm3and is less than 0.923 g / cm3, and which Ml (at 190 °C at 2.16 kg) according to ISO 1133-1 is more than 0.1 g / 10 min and is less than 0.5 g / 10 min.

[0099] The LDPE used in the intermediate layer is branched, which provides structural flexibility and resilience. This property makes it particularly suitable for extrusion processes, allowing it to be shaped efficiently without compromising stability. Additionally, it is bubble-stable, meaning it maintains integrity and prevents bubble formation during the extrusion process, which is crucial for ensuring a smooth, consistent product. Furthermore, this polyethylene helps to reduce pressure during extrusion, enhancing processing efficiency and reducing the risk of equipment stress, making it ideal for high-quality, stable production outputs.

[0100] In one variant of the invention, the thickness of the intermediate layer is more than 10 pm and less than 25 pm.

[0101] For example, the outer layer and / or inner layer has a proportion of LLDPE. Exemplarily, the amount of LLDPE in the intermediate layer is more than 5 % by weight and / or less than 45 % by weight.

[0102] In one variant of the invention, the amount of LLDPE in the outer layer and / or inner layer is more than 15 % by weight and / or less than 35 % by weight.

[0103] For example, the outer layer and / or inner layer has a proportion of LLDPE which density according to ISO 1183-1 is more than 0.915 g / cm3and is less than 0.917 g / cm3, and which Ml (at 190 °C at 2.16 kg) according to ISO 1133-1 is more than 0.5 g / 10 min and is less than 1.5 g / 10 min. RKW V684

[0104] 16

[0105] The LLDPE used in the outer and / or inner layer features long chains with minimal branching, making it more amorphous and less crystalline in structure. This configuration enhances the material’s mechanical properties, contributing to greater strength, flexibility, and durability in the film.

[0106] For example, the outer layer and / or inner layer has a proportion of LDPE. Exemplarily, the amount of LDPE in the intermediate layer is more than 55 % by weight and / or less than 95 % by weight.

[0107] In one variant of the invention, the amount of LDPE in the outer layer and / or inner layer is more than 65 % by weight and / or less than 85 % by weight.

[0108] For example, the outer layer and / or inner layer has a proportion of LDPE which density according to ISO 1183-1 is more than 0.919 g / cm3and is less than 0.923 g / cm3, and which Ml (at 190 °C at 2.16 kg) according to ISO 1133-1 is more than 0.1 g / 10 min and is less than 0.5 g / 10 min.

[0109] The LDPE in the outer layer and / or inner layer is characterized by its branched structure, making it highly adaptable for extrusion. This branching contributes to excellent bubble stability during the extrusion process, which ensures a smooth and consistent product without irregularities. Additionally, the material effectively reduces pressure during extrusion, promoting efficient flow and reducing wear on equipment. These combined properties make it an ideal choice for reliable and stable extrusion applications.

[0110] In one variant of the invention, the thickness of the outer layer and / or inner layer is more than 10 pm and less than 25 pm.

[0111] In a special variant of the invention, the outer layer has a proportion of a titanium dioxide TiC>2. This is preferably coated TiC>2. Due to the proportion of titanium dioxide, the outer layer is white, whereby an excellent reflection of sunlight can RKW V684

[0112] 17 be achieved and thus an excellent protection of the silage material can be realized.

[0113] For example, the titanium dioxide is integrated in a white polybatch. In a variant of the invention, the outer layer has a proportion of white polybatch of more than 5 wt.% and less than 20 wt.%.

[0114] The CIELAB color space is commonly applied in the evaluation and control of the color properties of polymer films across various industries. This color space provides a standardized, device-independent framework for measuring color and reflection, making it ideal for ensuring consistency and accuracy in the production of polymer films.

[0115] During the production process, manufacturers can use spectrophotometers to measure the L*, a*, and b* values of the films. These instruments capture how the film reflects or transmits light, and then convert that data into Lab values. This information helps assess whether the color of a film meets the specified target values or tolerances.

[0116] For example, the outer layer respectively the silage film has a reflection according to Lab value of more than 70 %, preferably more than 75 %, in particular more than 80 %. In this advantageous way, the high-energy solar radiation can be reflected and thus the contents of the silage film can be effectively protected.

[0117] In a variant of the invention, the inner layer has a proportion of a black pigment.

[0118] For example, the inner layer also has a proportion of black polybatch, whereby the proportion in the inner layer is more than 5 % by weight and less than 20 % by weight. RKW

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[0121] For example, the silage film has a thickness of less than 140 pm, preferably less than 120 pm, in particular less than 100 pm.

[0122] In a particularly advantageous variant of the invention, the thickness of the silage film is 90 pm.

[0123] For example, the silage film has a specific dart drop of more than 18 g / pm film thickness according to ISO 7765-1.

[0124] The determination of the impact resistance of a plastic film is carried out in accordance with ISO 7765-1 (“Plastics - Film - Determination of impact resistance by the free-falling dart method - Part 1 : Staircase method”). In this test method, a circular film specimen is clamped in a test holder so that it is fixed flat and wrinkle-free. A standardized, hemispherical dart with defined tip geometry and weight is dropped from a specified height onto the center of the specimen.

[0125] In one variant of the invention, the silage film has a specific dart drop of more than 20 g / pm film thickness according to ISO 7765-1 .

[0126] The weight of the dart is varied over a series of individual tests until a 50 % probability of failure is achieved, i.e. approximately half of the specimens fail while the other half withstand the impact. The impact energy is determined from the mass and drop height of the dart. The measured value is reported as the critical dart drop weight (g) that causes 50 % failure of the specimens.

[0127] For better comparability of different films, the dart drop value is additionally normalized to the film thickness in micrometers and expressed, for example, in g / pm. This allows a standardized representation of toughness and impact strength independent of the absolute film thickness. RKW V684

[0128] 19

[0129] For example, the silage film has a tensile strength in MD and TD according to ISO 527-3 of more than 35 MPa.

[0130] The tensile strength of the films is determined in accordance with ISO 527-3 (“Plastics - Determination of tensile properties - Part 3: Test conditions for films and sheets”). In this method, standardized film strips are clamped into a tensile testing machine under defined climatic conditions and stretched at a constant speed until rupture. During the test, the applied force and the elongation are continuously recorded. The tensile strength is reported as the maximum stress sustained by the specimen up to failure and is expressed in megapascals (MPa). In addition, further mechanical parameters such as the modulus of elasticity and the elongation at break can be determined, providing a comprehensive characterization of the mechanical properties of the films.

[0131] In one variant of the invention, the silage film has a tensile strength in MD and TD according to ISO 527-3 of more than 35 MPa.

[0132] For example, the silage film has an elongation at break in MD and TD according to ISO 527-3 of more than 550 %.

[0133] In one variant of the invention, the silage film has an elongation at break in MD and TD according to ISO 527-3 of more than 650 %.

[0134] For example, the silage film has a puncture resistance energy according to JAS P1019 of more than 10 mJ.

[0135] The puncture resistance is determined in accordance with JAS P1019, whereby a test sample of the silage film is clamped in a sample holder. The clamping device is designed so that the inside diameter is 10 mm. A probe with a rounded tip pierces the test sample at a constant speed. The force and elongation required for piercing are determined. RKW V684

[0136] 20

[0137] For example, the silage film has a puncture resistance according to JAS P1019 of more than 5 mJ, preferably more than 10 mJ, in particular more than 15 mJ. As a result, the silage film also withstands the demands of filling extremely well.

[0138] The tear resistance of the films is determined in accordance with ISO 6383-2 (“Plastics - Film and sheeting - Determination of tear resistance - Part 2: Elmendorf method”). In this test method, a film specimen with a predefined slit is clamped into a test holder and subsequently subjected to a swinging pendulum (Elmendorf apparatus). The pendulum propagates the slit through the specimen, and the expended energy is measured. The result is expressed as the tear force in Newton (N) or - for thin films - normalized in g / pm, providing a practical parameter for evaluating the film’s resistance against the propagation of an existing tear.

[0139] The silage film has a tear resistance in MD according to ISO 6383-2 of more than 20 g / pm, preferably more than 25 g / pm, in particular more than 30 g / pm. This makes the silage film particularly tear-resistant during the filling process as well as during transport and storage.

[0140] The silage film has a tear resistance in CD according to ISO 6383-2 of more than 30 g / pm, preferably more than 45 g / pm, in particular more than 60 g / pm.

[0141] The silage film has a Spencer puncture Energy according to ASTM3420 of more than 2000 mJ, preferably more than 2350 mJ, in particular more than 2700 mJ. The special structure and the specially selected raw materials produce a film for silage that can withstand the enormous mechanical stresses.

[0142] The Elmendorf test according to DIN 53128 determines the average force in grams or mN required to tear a sample after the tearing process has been initiated. During the test, one or more layers of the film are torn with a pendulum RKW V684 21 over a defined distance. The force applied during tearing is measured by the loss of potential energy of the pendulum.

[0143] In one variant of the invention, the silage film has a tensile strength in the machine direction according to Elmendorf DIN 53128 of more than preferably more than 15 —, in particular more than 20 —. This means that the silage tube is |im |im optimally prepared for the challenge during the filling process and effectively prevents the silage content from traveling.

[0144] According to the invention, a silage film is produced by a process in which an of at least one outer and at least one inner layer, a central layer, of at least one intermediate layer and of at least one functional layer are produced by coextrusion, wherein a proportion of up to 20 wt.-% masterbatch is incorporated into the polyethylene basis prior to extrusion, so that the film or the tube has an oxygen transmission rate of less than of less than 150 cm3 / m2 / 24h at 23 °C and 50 % relative humidity, measured according to ASTM D3985 or of less than 250 cm3 / m2 / 24h at 23 °C and 75 % relative humidity, measured according to EN 13207.

[0145] According to the invention, a film is used as recyclable silage film for storing grain, silage, warm or wet industrial products.

[0146] The PA-free and EVOH-free design of the silage film is achieved by using a specially engineered polyethylene in the functional layer, combined with an optimized masterbatch. This unique configuration enables genuine recyclability and high bubble stability during the extrusion process, even when using recyclates from the silage film. The advanced polyethylene structure enhances barrier properties, providing strength and protection without traditional barrier materials like EVOH and PA. The PE-based functional layer closely matches the mechanical and barrier properties of polyamide, effectively replacing RKW V684

[0147] 22 conventional barrier layers. Additionally, this innovative film design complies with the European Union’s new recyclability standards, demonstrating practical recyclability by eliminating polyamide while maintaining strong mechanical and barrier properties.

[0148] Further advantages and features of the invention are apparent from the description of an embodiment example with reference to drawings and from the drawings themselves.

[0149] In this connection

[0150] Fig. 1 a schematic representation of the silo film,

[0151] Fig. 1 shows a film 1 with seven layers as use for a silage film. Two functional layers 4 and 6 are directly adjacent to the central layer 5. An intermediate layer 3 is also arranged between the functional layer 4 and the outer layer 2 and also an intermediate layer 7 is arranged between the functional layer 6 ad the inner layer 8.

[0152] The thickness of the silage film 1 is 90 pm. The thickness of the outer layer 2 and inner layer 8 is 13 pm, the thickness of the central layer 5 is 6 pm, the thickness of the functional layer 4 and 6 is 15 pm, and the thickness of the intermediate layers 3 and 7 is 14 pm.

[0153] Further features and advantages of the invention are apparent from the description of examples of embodiments. RKW

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[0155] 23

[0156] Example 1 :

[0157] In this example, the outer layer 2 and the inner layer 8 are made of a proportion of LDPE, whereas outer layer 2 and the inner layer 8 comprise 75 % by weight of an LDPE with a MFI of 0.25.

[0158] In addition, the outer layer 2 and the inner layer 8 have a proportion of LLDPE, whereas the outer layer 2 and the inner layer 8 comprise 25 % by weight of an LLDPE with a melting temperature of 119 °C and whereas MFI of the LLDPE is 1.0.

[0159] The intermediate layers 3 and 7 are made of a proportion of LDPE, whereas the intermediate layers 3 and 7 comprise 20 % by weight of an LDPE with a MFI of the LDPE is 0.25. In addition, the intermediate layers 3 and 7 have a proportion of a further mLLDPE, whereas intermediate layers 3 and 7 comprise 65 % by weight of an mLLDPE and whereas MFI of the mLLDPE is 0.28.

[0160] The central layer 5 is made of a very soft uLLDPE, whereby the uLLDPE has a density of 0.910 g / cm3and a MFI of 3.

[0161] The functional layers 4 and 6 are made of a proportion of LDPE, whereas the functional layers 4 and 6 comprise 100 % by weight of an LDPE with a melting temperature of 116 °C and whereas MFI of the LDPE is 0.27.

[0162] The intermediate layers 3 and 7 also contain a proportion of 15 % by weight of a gas barrier masterbatch. The functional layers 4 and 6 achieve an oxygen permeability of the film 1 of less than 250 cm3 / m2d bar according to EN 13207.

[0163] The silage film 1 has a has a tensile strength in MD of 44 MPa and in TD of 42 MPa according to ISO 527-3, a specific dart drop of 19 g / pm film thickness according to ISO 7765-1 an elongation at break in MD of 650 % and in TD of 625 % according to ISO 527-3. RKW

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[0165] 24

[0166] Example 2

[0167] In contrast to Example 1, the functional layers in Example 2 are designed differently. The remaining layers are the same as in Example 1 .

[0168] The functional layers 4 and 6 are made of a proportion of LDPE, whereas the functional layers 4 and 6 comprise 85 % by weight of an LDPE with a melting temperature of 116 °C and whereas MFI of the LDPE is 0.27. The functional layers 4 and 6 also contain a proportion of 15 % by weight of a gas barrier masterbatch. The functional layers 4 and 6 achieve an oxygen permeability of the film 1 of less than 250 cm3 / m2d bar according to EN 13207.

Claims

RKWV684Silo filmClaims1 . A silage film (1 ) with a total thickness between 75 pm and 150 pm, comprising:- at least one outer (2) and at least one inner layer (8),- a central layer (5) composed of a soft polyethylene (PE), selected from linear low-density polyethylene (LLDPE) or low-density polyethylene(LDPE),- at least one functional layer (4, 6) arranged on either side of the central layer (5),- at least one intermediate layer (3, 7) positioned between each functional layer (4, 6) and the outer layer (2) or the inner layer (7), characterized in that at least one functional layer (4, 6) is composed of a special polyethylene that replaces conventional barrier layers, and is entirely free of any barrier layers, including polyamide (PA) or ethylene vinyl alcohol (EVOH).

2. Silage film according to claim 1 , characterized in that the silage film (1 ) has an oxygen transmission rate of less than 150 cm3 / m2 / 24h at 23 °C and 50 % relative humidity, measured according to ASTM D3985.RKW V68423. Silage film according to claim 1, characterized in that the silage film (1) has an oxygen transmission rate of less than 250 cm3 / m / 24h at 23 °C and 75 % relative humidity, measured according to EN 13207.

4. Silage film according to at least one of the proceeding claims, characterized in that the at least one intermediate layer (3, 7) comprises a masterbatch, containing particles that reduce oxygen permeability.

5. Silage film according to claim 4, characterized in that intermediate layer (3, 7) consist of less than 20 wt.-% of the masterbatch, wherein the masterbatch contains particles that create a tortuous path for gas and moisture molecules, thereby enhancing the barrier properties of the film.

6. Silage film according to claim 4 or 5, characterized in that the size of the particles ranges from 1 to 100 nm.

7. Silage film according to at least one of the proceeding claims, characterized in that at least one of the functional layer (4, 6) comprises a masterbatch, containing particles that reduce oxygen permeability.

8. Silage film according to at least one of the proceeding claims, characterized in that the film (1) has a water vapour permeability of less than 20 g / m2in 24 h according to ASTM D6701-01.RKWV6849. Silage film according to at least one of the proceeding claims, characterized in that the polyethylene (PE) of the functional layer (4, 6) has a density of more than 0.925 g / cm3and less than 0.930 g / cm3.

10. Silage film according to at least one of the proceeding claims, characterized in that the polyethylene (PE) of the functional layer (4, 6) has a molecular weight distribution (PDI) according to ISO 16014 of less than 2.

11. Silage film according to at least one of the proceeding claims, characterized in that the polyethylene (PE) of the functional layer (4, 6) has a short-chain branching (SCB) of 5 - 20 SCB per 1000 carbon atoms.

12. Silage film according to at least one of the proceeding claims, characterized in that the soft polyethylene (PE) of the central layer (5) has a density of more than 0.880 g / cm3and less than 0.912 g / cm3.

13. Silage film according to at least one of the proceeding claims, characterized in that the silage film (1) has a specific dart drop of more than 18 g / pm film thickness according to ISO 7765-1.RKWV684414. Process for the manufacture of a silage film (1) according to any one of claims 1 to 13 comprising the following steps: extrusion of at least one outer layer (2) and at least one inner layer (8), co-extrusion of a central layer (5), - co-extrusion of at least one intermediate layer (3, 7), co-extrusion of at least one functional layer (4, 6), characterized in that in at least one functional layer (4, 6) and / or intermediate layer (3, 7), a proportion of up to 20 wt.-% masterbatch is incorporated into the polyethylene basis prior to extrusion.

15. Use of a film (1) according to any one of claims 1 to 13 as fully recyclable silage film for the storage of grain, silage, warm or wet industrial products.

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