Process for producing a film, process for producing a granulate, a film and a plastic-forming line

Abstract

The invention relates to a process for producing a film having at least one layer that has a polymer blend comprising at least a first polymer and a second polymer, characterised in that at least two of the polymers involved are incompatible with one another, and in that the polymer blend is processed in an extruder. The invention also relates to a film comprising at least one layer that has a polymer blend comprising at least a first polymer and a second polymer, characterised in that at least two of the polymers involved are incompatible with one another. The invention also relates to a plastic-forming line, in particular a blown-film line or flat-film extrusion line, for producing a film having at least one layer that has a polymer blend comprising at least a first polymer and a second polymer, characterised in that at least two of the polymers involved are incompatible with one another.

Description

[0001] Method for producing a film, method for producing a granulate, a film and a plastics molding plant

[0002] Description

[0003] The invention relates to a method for producing a film having at least one layer with a polymer blend, comprising at least a first polymer and a second polymer, the invention further relates to a film having at least one layer with a polymer blend with at least a first polymer and a second polymer and further relates to a plastic molding system for producing a film having at least one layer with a polymer blend, comprising at least a first polymer and a second polymer.

[0004] Plastics are polymers consisting of long chains of molecules. Unlike natural polymers, such as cellulose or rubber, synthetic plastics can be precisely controlled in their properties and behavior. This makes them suitable for a wide range of applications in industry and everyday life.

[0005] One of the most important properties of plastics is their moldability. By heating and then cooling them in a mold, they can be molded into almost any desired shape. The moldability of plastics makes it possible to create complex geometries and details that would be difficult or even impossible with other materials.

[0006] In addition to their formability, plastics also have a multitude of other properties that make them attractive for a wide range of applications. For example, they are lightweight, robust, durable, waterproof, chemical-resistant, and electrically insulating. These properties make plastics the ideal material for packaging, protective covers, components, and much more. The unparalleled success of plastics since their availability is due to the extremely wide range of applications this material has to offer and its diverse properties. Plastics are characterized by their very low density, widely adjustable mechanical properties, good processability, and, last but not least, excellent reprocessability, as well as a host of other properties.

[0007] Different molecular structures as well as adapted preparation and processing methods make it possible to produce "custom-made materials" that can then be used for a wide variety of applications.

[0008] However, there are also disadvantages to using plastics. Many plastics are not biodegradable and can cause environmental pollution if not disposed of properly. Furthermore, some plastics can release toxic substances over time that can be harmful to health. Therefore, it is important to use environmentally friendly and safe processes in the production and disposal of plastic products. The reuse of plastics is particularly relevant.

[0009] In recent years, the development of biodegradable plastics has also become increasingly important. These plastics are partly made from renewable raw materials and can be broken down by microorganisms, for example, without releasing toxic substances.

[0010] Plastics can be recycled in several ways, depending on their chemical composition and condition. One option is mechanical recycling, in which the plastics are broken down and processed into new products. This method is easiest for plastics that are still in good condition and can be easily broken into small pieces. Another option is chemical recycling, in which the plastics are broken down into their component parts and then processed into new plastic products. This method is suitable for plastics that are too dirty or damaged to be recycled through mechanical processes. Another option is thermal recycling, in which the plastics are burned at high temperatures to generate energy. This method is best suited for plastics that can no longer be recycled.

[0011] Plastics are often made from blends of different polymers because these blends can improve certain properties that are important for the intended application. For example, the tensile strength or durability of a plastic can be increased by combining different polymers. Blends of different polymers can also help reduce manufacturing costs by combining inexpensive polymers with more expensive ones. Another reason plastics are often blends of different polymers is that they are easier to process and mold, which is beneficial for the industrial production of large quantities of plastic products.

[0012] However, the existence of the resulting multitude of plastic types sometimes leads to problems with collection and recycling. For this reason, these plastics were long considered non-recyclable or only of very limited recyclability. The challenge regarding recyclability is compounded by the fact that plastic products often consist of different types of plastic, such as multilayer films and / or film composites, so-called laminates. In such cases, the recyclates are a mixture of different types of plastic.

[0013] Depending on the condition of the recyclate, the recycling methods of material, raw material and energy recycling are chosen.

[0014] Mechanical recycling is the reprocessing of plastic waste into new products without significantly changing the molecular structure of the polymer molecules. This process is usually achieved by remelting the plastics. Materials recycling is a process in which waste materials consisting of various materials are reused to create new products. This process is often used for plastics, paper, glass, and metals. Unlike conventional recycling, in which materials are broken down into their original components and then transformed into new products, mechanical recycling focuses on reusing materials in their existing state. This process can help conserve resources and reduce the environmental impact of waste.

[0015] In material recycling, a distinction is made between direct processing and regranulation. Direct processing occurs when new products are manufactured directly from waste through a single processing step. This approach is currently only used for mixed plastic waste for the production of thick-walled, low-quality molded parts. On the other hand, high-quality, single-grade waste is directly recycled into the production process through in-house recycling and thus processed directly into new products.

[0016] In most cases, however, regranulation is used, i.e. the plastic waste is melted after processing by extrusion in order to produce high-quality granules, which are then processed by the plastics processors into corresponding products in the same way as new material.

[0017] Plastics regranulation is a process in which used or worn-out plastics are cut into small pieces and then processed into small pellets. These pellets can then be processed into new plastic products, enabling the recycling of plastics. Regranulation is a form of mechanical recycling technology and is commonly used for plastics such as polyethylene, polypropylene, and polystyrene. It is a cost-effective and environmentally friendly alternative to producing plastic products from crude oil.

[0018] The main advantage of granulation is that the quality of the regranulate can be specifically influenced, e.g. by specifically adapting the extrusion process to the properties of the feedstock, and that the processor receives an easy-to-handle regranulate which can be processed essentially like new material.

[0019] The decisive factors for whether material recycling is possible are the degree of contamination, the mixing with other plastics or other foreign substances such as printing inks or adhesives, and the molecular structure or possible cross-linking of the polymer molecules. The problem with mixing plastics is that most plastics are incompatible with each other.

[0020] Typically, plastic polymers belonging to the same polymer class are miscible with each other and can be used in a blend. Examples of such polymers are polyethylene (PE), polypropylene (PP), and polystyrene (PS), all of which are polyolefins and are made from alkenes through chain polymerization. These polymers generally miscible with each other and can be processed into a wide variety of plastic products. However, polymers made from different chemical structures can also be used in a blend as long as they are carefully selected and compatible. It is important to note, however, that not all polymers are compatible with each other, and some blends may cause undesirable properties. For this reason, it is important to plan and test carefully when using plastic blends to ensure that the desired properties are achieved.

[0021] The following list describes the miscibility of some commonly used polymers.

[0022] Scale from 1 (easily mixable) to 6 (poorly mixable).

[0023] In this context, miscibility refers to the compatibility of different thermoplastics.

[0024] Mixtures of two or more different polymers are called polymer blends or polyblends.

[0025] A polymer blend is a mixture of two or more polymers, either alternatively or cumulatively, bonded together by chemical or physical interactions. These blends are often used to improve certain properties of plastics by combining different polymers. For example, the tensile strength or durability of a plastic can be increased by blending different polymers together. Polymer blends are also often used to reduce the manufacturing costs of plastic products by combining inexpensive polymers with more expensive ones.

[0026] The material properties of the polymers complement each other in such polymer blends; the properties of the blend depend on whether and to what extent the polymers involved in the blend are compatible with each other, i.e., whether they mix completely or form separate phases. The mixing processes required for this are carried out in screw extruders (single-screw extruders, twin-screw extruders, planetary roller extruders, etc.).

[0027] When mixing polymers, a distinction must be made between

[0028] • homogeneous mixtures of compatible polymers,

[0029] • Mixtures of limited compatibility polymers and

[0030] • to distinguish between heterogeneous mixtures of incompatible polymers. Whether a two-component system is miscible or not can be derived from thermodynamic considerations. Whether a two-component system is miscible or not can be derived from thermodynamic considerations: A homogeneous mixture requires a free enthalpy of mixing AGm < 0. A polymer blend with a positive Gibbs energy of mixing (AGm > 0) is a heterogeneous mixture of incompatible polymers.

[0031] Thermodynamic considerations in plastics refer to the application of the principles of thermodynamics to understand and describe the properties and behaviors of plastics. In the context of plastics, thermodynamic considerations can be used to understand how the temperatures and states of plastics change under different conditions and how this affects their properties. For example, thermodynamic considerations can help understand the melting behavior of plastics and predict how their structure and properties change upon heating and cooling.

[0032] Thermodynamic considerations are also used to investigate the interactions between plastics and other materials and to understand how these interactions affect the properties of plastics. Homogeneous mixtures of compatible polymers

[0033] Although the number of compatible polymers is limited, they are of some importance. Their properties can be varied linearly with the proportion of homopolymers. The following blends of compatible polymers are of particular commercial importance:

[0034] Natural rubber with polybutadiene and other elastomers

[0035] • Polyphenylene ether (PPE) with polystyrene (PS)

[0036] • Polyamides, e.g. PA 6 with PA 10

[0037] • Polyethylene with polyisobutylene

[0038] Mixtures of homopolymers with the same monomer base often exist.

[0039] The monomer base is the foundation from which polymers are made. A monomer is a molecule that can combine with other monomers to form linked molecular chains. These linked molecular chains form the basis of polymers and determine their chemical properties and behavior. The monomer base of a polymer can consist of a single monomer, known as a homopolymer, or of several different monomers, known as a copolymer. The monomer base of a polymer has a decisive influence on its properties and behavior, and the choice of monomer base is an important factor in the development and production of plastics.

[0040] Homopolymers are plastics that consist of a single polymer. This means they are composed of identical monomers that do not differ in their chemical structure and properties. Homopolymers are produced, for example, by chain polymerization, in which a large number of monomers are joined together to form a long, linked molecular chain. The properties of homopolymers are generally very uniform and can be easily predicted because they consist of uniform molecules. Examples of homopolymers are polyethylene, polypropylene, and polystyrene. In contrast to homopolymers, copolymers are plastics composed of two or more monomers.

[0041] A good example of blends of homopolymers with the same monomer base are blends of different polyethylenes, especially blends of LDPE and LLDPE. This allows the difficult-to-process LLDPE to be adapted to existing machinery, especially in the production of tubular film. The blend is usually created during the extrusion process.

[0042] LLDPE stands for low-linear-density polyethylene, a material made from polyethylene. It typically has a low linear density. It is often used in the manufacture of plastic packaging, films, and bowls because it is lightweight, durable, and cost-effective. The low linear density of LLDPE results in a lower density of the material, resulting in lower mass and increased flexibility.

[0043] Mixtures of limited compatibility polymers

[0044] The most significant applications for blends of limited-compatibility polymers are found in rubber processing, where virtually all elastomers are blended together. Rubber processing is the process by which raw rubber is transformed into products such as tires, rubber belts, and other rubber products. This process typically involves several steps, including foaming, kneading, and calendering the rubber. However, the exact steps and methods of rubber processing depend on the type of final product being produced.

[0045] An elastomer is a material that is highly stretchable and elastic. It has the ability to return to its original shape after being stretched or subjected to stress. Elastomers are widely used in industry to produce things like rubber, caoutchouc, and rubber bands. The production of tires and other rubber products that meet today's requirements would not be possible without the ability to achieve the highest performance by blending different polymers.

[0046] Heterogeneous mixtures of incompatible polymers (multiphase mixtures)

[0047] Mixtures of incompatible polymers are widely used. Most polymers are generally immiscible at the molecular level, or in other words, incompatible. In a mixture of two incompatible polymers, the blend consists of a continuous phase (also called the main phase) and a dispersed phase (also called the dispersed phase or secondary phase). In contrast to homogeneous mixtures of (two) compatible polymers, where only one glass transition temperature is discernible, heterogeneous mixtures of two incompatible (immiscible) polymers exhibit two glass transition temperatures. Plastic waste from multi-component injection-molded parts or films such as barrier films (e.g., PE / PA, PE / EVOH, PE / PA / EVOH, etc.) or laminates (e.g., PET / PE, PET / PP, PA / PE, etc.) are typical examples of heterogeneous mixtures of incompatible polymers when they are remelted after use during recycling.

[0048] The glass transition temperature of plastics is the temperature at which a plastic changes from a solid to a viscous state. The glass transition temperatures of plastics can vary depending on the type of plastic and its composition. However, the glass transition temperature of plastics generally ranges from approximately 100 to 400 degrees Celsius. The glass transition temperature, especially for semi-crystalline plastics, is much lower than 100 °C, namely between -150 °C and +400 °C.

[0049] The glass transition or softening temperature (TG) is the temperature at which a glass exhibits the greatest change in deformability. Glass is a solidified liquid. Glasses are formed, for example, by what is commonly referred to as inorganic glasses—such as window glass—but also by organic glasses such as amorphous plastics. This so-called glass transition separates the brittle, energy-elastic region below (=glass region) from the soft, entropy-elastic region above (=rubber-elastic region). The transition to the flow region of the amorphous plastic is smooth.

[0050] Semi-crystalline plastics have both a glass transition temperature, below which the amorphous phase 'freezes' (accompanied by embrittlement), and a melting temperature at which the crystalline phase dissolves.

[0051] When a plastic is heated to its glass transition temperature, it becomes malleable and can be molded into various shapes. After being molded into the desired shape, it is allowed to cool to solidify again. The glass transition temperature is an important factor in the manufacturing of plastic products such as packaging, toys, and electronic components.

[0052] The structure of a heterogeneous mixture is characterized by the extent of the dispersed phase in the continuous phase. The mechanical properties of such a heterogeneous mixture generally depend on the degree of dispersion of the dispersed phase and the adhesion between the phases in the solid state. In particular, it is desirable for the particles of the dispersed phase to be as small as possible and evenly distributed in the homogeneous phase. Without special intervention, the dispersion, i.e., fineness, and distribution of the dispersed phase, as well as the adhesion, are inherently poor. To improve mixing, i.e., the dispersion and distribution of the dispersed phase, processing machines, especially extruders, should be equipped with suitable mixing elements.Extruders and / or mixing elements that generate not only shear but also extensional flow are particularly effective for producing fine particles. Modern kneading machines (e.g., planetary roller extruders or twin-screw extruders) can produce particles of the dispersed phase ranging in size from a few nanometers to micrometers by dispersive mixing. This allows for a uniform dispersion of this phase in the homogeneous phase while simultaneously achieving good distributive mixing.

[0053] At the same time, additives called compatibilizers can be used to bond the phases together by grafting, thus improving adhesion. Compatibilizers can be copolymers, half of whose chains consist of monomers that are compatible with one of the two phases. These are incorporated into one of the two phases and thus ensure that the phases are anchored together. Both – good mixing and good adhesion – have a positive effect on the mechanical properties.

[0054] Compatibilizers are chemical additives used to improve the compatibility of different polymers in a blend. They are often used when different polymers are blended together to improve the properties and performance of the material. Compatibilizers can work in different ways, for example, by improving adhesion between the polymers or by influencing the rheological properties of the blend. In either case, they serve to improve the properties of the blend and facilitate the processing and use of the material.

[0055] The rheological properties of a mixture refer to its behavior and properties in the liquid state. Rheology is the branch of physics that deals with the deformation and flow of materials, and the rheological properties of a mixture describe how it flows and deforms under certain conditions. These properties are important because they affect the processing and use of the mixture, for example, when casting, extruding, or injecting materials. The rheological properties of a mixture can be influenced by various factors, such as the composition of the mixture, temperature, or pressure.

[0056] Nevertheless, it should not be overlooked that material recycling is usually associated with a change in quality and frequently a deterioration in quality. This is due to the fact that the molecular structure changes at least slightly with each processing step and sometimes even during use. Oxygen present during processing can lead to oxidation, temperature influences lead to thermally induced chain degradation, and the presence of moisture leads to hydrolytic chain scission. Chain scission can also be induced during use in various ways through oxidation, by substances diffusing into the plastics, or by exposure to UV light. Furthermore, even after processing, the used plastics are still at least slightly mixed with other polymers or contaminated.

[0057] It's impossible to make a general statement about which properties deteriorate and which remain constant during reprocessing. Therefore, before manufacturing products from recycled material, it's important to check what requirements the material must meet and what requirements the recycled material meets.

[0058] A recyclate is a material made from recycled plastics. Unlike virgin plastics, also known as new plastics, which are derived from crude oil, recyclate is made from previously collected used plastics.

[0059] An example of an undesirable change in recyclate is the increase in the melt flow index (MFI) caused by molecular weight reduction in multiply extruded PE. In this context, in the case of materials recycling, direct processing of the waste without prior processing is advantageous. The melt flow index (MFI) is a measure of how easily a plastic flows when melted. It is usually measured using a standardized test method in which a specific amount of the plastic is allowed to flow at a specific temperature and load. The higher the MFI value, the more easily the plastic flows during the measurement. The MFI is often used to assess the quality and processability of plastics.

[0060] Another problem with processing different plastics together is their often very different processing temperatures: PE-LD can be melted at 160 °C and at the same time has a very wide temperature window, while PA6 / 6.6 copolyamide and polyamide 6 or even PET, for example, can only be processed above 245 °C or above 260 °C.

[0061] The different processing temperatures result from the different temperatures at which the different plastics melt. These different temperatures are not atypical for heterogeneous mixtures and, in the case of the aforementioned multi-component plastic waste, are even typical. A so-called DSC curve can visualize these different melting temperatures, or more precisely, the melting ranges.

[0062] A DSC curve is typically a curve generated using the DSC (differential scanning calorimetry) method. DSC is an analytical technique used to determine changes in heat capacity and thermal conductivity of materials. The curve shows the changes in the thermal conductivity or heat capacity of the material as a function of temperature. It is often used to investigate and compare the physiochemical properties of materials.

[0063] Contaminants still present in the material can also sometimes cause problems. Contaminants can be in the form of inorganic particles (e.g., aluminum or sand) or organic contaminants (e.g., grease, water, contents, or paper) that have not been removed by processing. This can lead to markings, defects, incompatibilities, or interactions with the polymer molecules, which then lead to a deterioration in quality.

[0064] Due to these problems in material recycling, a number of options have been developed that can be used in the regranulation of waste or directly in the reprocessing into a new product to improve the material quality:

[0065] • Use of stabilizers,

[0066] • Use of compatibilizers,

[0067] • Incorporation of fillers and reinforcing materials,

[0068] • Removal of solid dirt particles by melt filtration,

[0069] • Removal of volatile components by melt degassing.

[0070] Degassing

[0071] Degassing refers to the process by which gases are removed from a material. In the context of plastics recycling, degassing is an important step to improve the quality of the recycled material. During the recycling process, air bubbles and other gases can accumulate in the plastic, which can impair the quality and processability of the material. Degassing removes these gases, resulting in a better final product. There are several ways degassing can be performed in plastics recycling, for example, by using vacuum techniques or by adding degassing agents.

[0072] Degassing offers the possibility of removing low-molecular-weight components, gases, or air from the melt during the processing process by extrusion, just as it does for virgin materials. However, the substances to be degassed vary somewhat due to the specific composition of the recycled materials.

[0073] Degassing tasks that occur more frequently in plastics recycling are:

[0074] • Drying: Removal of residual moisture, which may eliminate the need for time-consuming and expensive pre-drying of the material; blistering and molecular weight reduction through hydrolysis can be prevented.

[0075] • Shift in the equilibrium: If low molecular weight components are removed, especially from polycondensates, the equilibrium is shifted towards high molecular weight chains and a molecular weight increase occurs.

[0076] • Removal of external contaminants: Volatile, mostly organic compounds that adhere to the plastics in the form of contaminants are removed from the melt, e.g. fats, oils and, in some cases, printing inks or varnishes.

[0077] • Removal of internal contaminants: Substances that have diffused into the plastic during use and that cannot be removed by a washing process are removed by degassing, e.g. gasoline, diesel, antifreeze.

[0078] • Removal of low-molecular degradation products: Degradation products released during processing or use, which are in the form of chain fragments, monomers or oligomers and which permanently impair the use and processing properties of the plastic, are removed.

[0079] • Degassing of solvents: Solvents that have entered the material due to partial purification and separation steps during processing are removed. However, degassing also removes some substances that should remain in the material. These can include short-chain polymer components as well as added additives, particularly stabilizers, antioxidants, light stabilizers, plasticizers, etc.

[0080] By deliberately increasing the melt temperature, the effectiveness of the decomposition of by-products, such as printing inks, can be significantly increased. This increase in melt temperature is accompanied by an increased degassing line, which can serve to remove unwanted by-products and / or (foreign) substances. As the temperature increases, the decomposition of the printing inks becomes more intensive, which can release harmful substances and gases.

[0081] The melt temperature is preferably set at the respective upper end of the temperature range of the processed material, with a temperature range of approximately 90°C to 350°C, preferably between 110°C and 250°C, being preferred. This targeted increase in the melt temperature at the upper end of the temperature spectrum of the processed material has proven particularly advantageous for ensuring precise decomposition of the by-products. At the same time, the structural integrity of the actual polymer is ensured by precise control of the melt temperature, thus enabling safe processing.

[0082] The escaping gases can be captured and subjected to special post-treatment, for example, to minimize environmental impacts. This approach not only contributes to the optimization of production processes but also emphasizes the environmentally conscious management of emissions generated during decomposition.

[0083] Melt filtration

[0084] In melt filtration of plastics, the material is passed through a filter element as it melts to remove impurities and other solids from the plastic. The plastic is passed through a filter element under pressure and at high temperatures, which filters out the solids. Melt filtration is an important step in plastics recycling because it helps improve the quality of the recycled material and remove as many contaminants as possible. It is often used in combination with other techniques, such as degassing, to make the recycled material as pure as possible.

[0085] Filtration, filtering, or filtration generally refers to the separation of solid or liquid particles from fluids using a filter medium. In extrusion, filtration therefore serves the purpose of removing all types of foreign particles, according to a selected filter fineness, and thus providing the purest possible melt.

[0086] This problem arises to a greater extent in the processing of plastic waste, which, despite complex cleaning steps during processing, still contains a greater amount of contamination than is the case with new plastic products.

[0087] For process optimization and economic reasons, melt filtration must meet the following requirements:

[0088] • Filtration at approximately constant pressure and constant temperature

[0089] • Filter change without interrupting and / or affecting production

[0090] • Minimal additional residence time of the melt

[0091] Minimal pressure drop in the filter media

[0092] Maximum filter service life. Due to the sometimes very high levels of contamination found in plastic waste, conventional filtration systems for new materials quickly reach their limits with regard to these requirements. A foreign body content of just 0.3% by volume is already considered a very large amount of contamination for filtration, and even for a screen wheel filter, which is a continuously operating filter system, an upper limit of 0.5% by volume of contamination is considered to be economical.

[0093] Incorporation of additives

[0094] The use of additives in the upgrading of plastic waste can have various benefits. Firstly, additives can help improve the quality of the recycled material by enhancing certain properties such as hardness, weather resistance, or color. Secondly, additives can help increase the processability of the recycled material by improving melting properties and making the material easier to process. Finally, additives can also help increase the durability of the recycled material by delaying its aging. Overall, additives help improve the performance of the recycled material and increase its value as a raw material.

[0095] The upgrading of plastic waste through additives can be divided into the incorporation of additives that are also used for new plastic products and the incorporation of additives that have been specifically developed for use in the reprocessing of plastic waste.

[0096] In the first case, recycled plastics can be enhanced with, for example, mineral fillers, reinforcing fibers, color pigments, lubricants, plasticizers, etc. The specific selection depends essentially on the intended use of the plastic. However, there are limitations to the enhancement. For example, mixed plastic waste usually develops a gray, green, or brownish color. This means that even with the use of color pigments, only difficult-to-define colors can be achieved. While black, dark blue, or brown colors are possible, lighter colors in particular cannot be achieved.

[0097] Stabilizers are chemical additives used in plastic manufacturing to improve the chemical stability of the plastic. They are often used to protect the plastic from damage caused by UV radiation, heat, and other external influences that can affect the material's chemical structure. Stabilizers can also help delay the aging of the plastic and extend its lifespan. Different types of stabilizers are typically used depending on the type of damage the plastic is likely to be exposed to and the properties it is intended to have.

[0098] For the proper use of stabilizers, it is important to know the exact history of the recyclate. This includes the original stabilizer content, as well as any damage caused by previous processing steps and previous use. Stabilizers have been specifically developed for this purpose to prevent molecular weight degradation and darkening during reprocessing.

[0099] Deterioration of polymer materials occurs primarily due to heat, atmospheric oxygen, light, moisture, high-energy radiation, and microbial influences. Therefore, different stabilizers or combinations of these must be used for the different influences and degradation mechanisms:

[0100] Antioxidants: Protect polymers against oxidative degradation by oxygen, especially under the simultaneous influence of heat during processing. Metal: Protect polymers from accelerated thermo-oxidative degradation.

[0101] Degradation, deactivators: which in some polymers is triggered by the presence of metals such as copper or iron.

[0102] • Light stabilizers: Protect polymers against light-induced degradation.

[0103] • Biostabilizers: Microorganisms can also attack and damage polymers, especially additives such as the plasticizers in PVC.

[0104] Stabilizers work by reacting more rapidly with the oxygen or light present, for example, and thus protecting the polymer itself from damage. However, this also means that the stabilizer is gradually consumed, and even after complete consumption, the polymer can still be damaged. Therefore, the dosage of stabilizers is crucial. This generally ranges between 0.05 and 5.0 wt.% and is initially designed for a single use of the polymer. Therefore, re-stabilization is required for reprocessing.

[0105] In addition to the intended application and the associated environmental influences, as well as the processing conditions, the dosage of stabilizers is also determined by the polymer types, which vary considerably in oxidation and light sensitivity. Thus, optimal post-stabilization must consider the pre-damage, the existing residual stabilizer content, the reprocessing conditions, and the subsequent application. Nevertheless, it must be noted that post-stabilization can only largely maintain the properties of the recyclates and cannot improve them.

[0106] Another important additive in the reprocessing of plastics is compatibilizers. The goal of compatibilization is to improve the properties of a heterogeneous mixture of incompatible polymers. Two different compatibilization strategies exist for this purpose: The first strategy involves adding non-reactive compatibilizers (e.g., copolymers, nanoparticles, or ionomers) to the polymer blend, improving interphase adhesion, inhibiting phase coalescence, and reducing the degree of dispersion.

[0107] Compatibilizers are mixed into the raw granules in quantities of a few percent by weight.

[0108] There are essentially two ways to improve the compatibility of a two- or multi-component heterogeneous mixture:

[0109] • Addition of non-reactive compatibilizers: Addition of an additional, e.g. third, component, such as block or graft copolymers or ionomers whose components exhibit improved compatibility with both incompatible components of the plastic mixture. Block or graft copolymers are polymers consisting of two or more different monomer units that are linked together, with chains of another monomer type adjoining a main chain formed from a monomer in a comb-like manner. In contrast to linearly linked polymers, in which the monomer units are strung together in a single chain, block or graft copolymers have multiple sections with different monomer units. These sections can have different chemical properties and thus influence the properties of the overall polymer.Block or graft copolymers are often used in the production of plastic blends to act as a bonding partner between polymers that are not readily compatible with each other. The addition of nanoparticles as non-reactive compatibilizers is also known.

[0110] • Reactive compatibilization: Modification of one or both incompatible components by grafting functional groups that improve compatibility with the other component. Compatibilization, or modification, occurs during blend production. This method is also called reactive compatibilization, and the process is called reactive extrusion. Twin-screw extruders are particularly well-suited for the tasks associated with reactive extrusion.

[0111] Addition of non-reactive compatibilizers

[0112] The addition of a copolymer, i.e., a polymer with at least two different monomer units, to a heterogeneous mixture of incompatible polymers can reduce the interfacial tension between the phases, thus weakening phase separation and promoting the formation of a finely dispersed phase. This process is similar to the emulsification of immiscible liquids. Block copolymers (diblock, triblock, and multiblock copolymers) or graft copolymers are typically used. A prerequisite for the use of copolymers as compatibilizers is that all polymers in the blend must interact with one of the segments (blocks) of the copolymer. A typical example of a triblock copolymer, which is already used as a compatibilizer for various material systems, is styrene-ethylene-butylene-styrene, a thermoplastic elastomer.SEBS has been successfully used in PET / PE and PET / PP blends to improve the mechanical properties: The use of the compatibilizer led to a more homogeneous morphology, increased elongation at break and impact strength.

[0113] The same compatibility-enhancing effects as with compatibilization with copolymers can also be achieved with nanoparticles (NPs). The prerequisite for stabilizing the droplets—the dispersed phase—is that the NPs migrate to the interface between the matrix and the dispersed phase and exhibit an equal attraction to the polymers present in the blend. The NPs can have different shapes (spherical or platelet-shaped), chemical structures (silicon dioxide, calcium carbonate, organically modified montmorillonite), and sizes, as well as a surface coating (usually with organic molecules). Ionomers are thermoplastic copolymers that possess a "pendant" ionic group and thus have a relatively low ion concentration.Due to the secondary valence forces (van der Waals forces, dipole-dipole interactions, hydrogen bonds) present in these thermoplastics, strong electrostatic forces exist between the polymer chains. An example of an ionomer is ethylene-methacrylic acid copolymer. This compatibilizer is used, among other things, to compatibilize a recycled blend of PE and PA and results in increased tensile strength, yield strength, elongation at break, impact strength, and hardness compared to the polymer blend without the compatibilizer. The intermolecular forces reduce the interfacial tension between the different phases.

[0114] In addition to monomers, another thermoplastic, namely EVA, is added as a compatibilizer.

[0115] Reactive compatibilization

[0116] The grafting of functional groups onto one or more components of a heterogeneous mixture of incompatible polymers to increase compatibility is referred to as reactive compatibilization. The compatibilizers are often copolymers. The homogenization of the incompatible polymers is promoted by intermolecular forces of attraction between the copolymer and a component of the polymer mixture due to their polarity, and by the copolymer forming a chemical bond with another component of the blend. The more polar the compatibilizer, the greater the intermolecular interactions between the phases.

[0117] The most commonly used compatibilizers in the plastics industry are maleic anhydride (MA)-grafted copolymers. These are reactive toward hydroxyl (OH) and amino (NH2) groups and are therefore particularly useful in mixed plastic waste containing polymer chain ends with one of these two groups. The MA-grafted copolymers form a covalent bond with one of the blend partners, resulting in an improvement in mechanical properties.

[0118] In general, anhydrides of unsaturated dicarboxylic acids can be used to introduce an anhydride group as a reactive group. These are preferably produced using the so-called "grafting from" method of graft copolymerization. Reactive compatibilization of a PE / PA blend is possible, for example, with PE-g-MA, i.e., a polyethylene grafted with maleic anhydride. Melting and compounding the thermoplastics with the compatibilizer causes the PE backbone of the copolymer to develop van der Waals forces with the polyethylene, and the anhydride group reacts with the amino group of the polyamide. Compared to the non-compatibilized blend, the dispersed phase exhibits a more uniform microstructure, the particle size decreases significantly, and the tensile properties improve.

[0119] Polyethylene grafted with maleic anhydride can also be used as a compatibilizer for PE / PET blends. The anhydride group of the compatibilizer reacts chemically with the hydroxy group at the chain end of the PET, and the PE portion of the PE-g-MA is miscible with the PE component of the polymer blend due to physical bonding forces.

[0120] Other compatibilizers based on maleic anhydride are, for example, SEBS-g-MA, for example for PE / PET or PE / PA blends, and PP-g-MA, for example for PE / PP systems, or EVA-g-MA and EVB-g-MA, for example also for PE / PET or PE / PA blends.

[0121] Alternatives to maleic anhydride-grafted copolymers are those with an unsaturated epoxide, such as glycidyl methacrylate (GMA) as the reactive group. In addition to the aforementioned GMA and MA, acrylic acid (AA), ethylene-vinyl acetate copolymer (EVA), and maleimide (MI) are also common functional groups that are either grafted onto polyolefins or copolymerized into compatibilizers. Reactive extrusion can also be used to optimize compatibility through radical formation: The co-homogenization and processing of incompatible plastics with a radical initiator in an extruder leads to the formation of macroradicals. These reactive polymers are capable of forming a covalent bond with the other blend partners, thus enabling the formation of grafted or crosslinked copolymers.The degree of crosslinking of the polymer blend increases through the use of radical initiators during mechanical recycling, thus increasing compatibility. However, the presence of radicals during plastics processing can also lead to oxidative degradation and chain degradation, which is why reactive extrusion must aim to maximize compatibilization and minimize chain scission.

[0122] Compatibilizers are used for the combined processing of plastic waste whose separation is either technically impossible or economically impractical, such as the reprocessing of coextruded plastic waste consisting of different, incompatible polymers. These include multilayer film waste made of PE and PA, PE and EVOH, or PE and PET, or blends and laminates such as PE / PET, PE / PA, PP / PET, etc. Compatibilizers also optimize the combined processing of plastic fractions from household waste (PE, EVA, ionomers, COC, PP, PET, PA, EVOH, PS, etc.).

[0123] Coextruded plastics are plastics consisting of multiple layers produced simultaneously using an extrusion process. In this process, the different layers of plastic are passed through a die and extruded simultaneously, bonding them together. Coextruded plastics often have different properties that vary from layer to layer. For example, one layer of plastic may have certain characteristics, such as hardness or resistance to weathering, while another layer may have different properties, such as flexibility or transparency. Coextruded plastics are often used in the production of packaging, films, and other products where different properties are required.While coextruded films are typically manufactured in a single step, in the case of laminates, the individual films that comprise the laminates are produced in separate extrusion processes and then combined into a composite in one or more subsequent processes; this is known as lamination. This creates the typical laminates made up of two or three films.

[0124] Production or processing waste (plastics from post-industrial origin: "PIR" = Post Industrial Recycling) is waste generated during the production of plastics. This waste can take various forms, such as chips, dust, foams, or incompletely finished products. It often arises from the processing of plastics, for example, by extruding, punching, sawing, or grinding the material. Production or processing waste represents an important resource that can be reused or recycled to reduce the environmental impact of waste and conserve valuable resources.

[0125] Production or processing waste is generally largely uncontaminated and is therefore highly suitable for material recycling. If the waste is sorted, i.e., it consists predominantly of a single raw material, such as PE film, it is returned directly from the production plant to the materials cycle. More specifically, after processing, it is directly processed into new products, e.g., through processes such as extrusion, injection molding, blow molding, etc., whereby the processed materials are often mixed with virgin materials. In this case, it is referred to as in-house recycling.

[0126] However, if the production or processing waste involves composite products, such as injection-molded parts made of multiple components or films made of multiple layers and / or film laminates constructed from different basic raw materials such as PE, EVA, ionomers, COC, PP, PET, PA, EVOH, and others, as well as printed films, etc., the processing now initially takes place in a separate processing step. This makes it possible to specifically influence the material properties of the recyclates. This can be achieved by adding virgin materials, additives, reinforcing materials, or fillers, through reactive extrusion, or through degassing. The end result is a recyclate that closely resembles the granules of virgin materials in appearance.

[0127] Post-consumer recycling refers to the recycling of plastics that have already been used by end users. Unlike PIR waste recycling, which uses plastics directly from production, post-consumer recycling uses plastics that have been purchased and used by consumers and subsequently disposed of as waste. These plastics can come from various sources, such as packaging, household appliances, furniture, or other products. Post-consumer recycling is an important step in reducing plastic waste and conserving valuable resources.

[0128] Waste that arises after use - i.e. from the post-consumer sector ("PCR" = Post Consumer Recycling) - places higher demands on material recycling than production or processing waste, but in principle does not differ from those.

[0129] An example of waste that is currently only subject to very limited recycling is laminates made of PET and PE films. These are available in large quantities both as PIR and PCR products. At least one film of the laminate consists predominantly of PE raw materials with a thickness of 20 to 200 μm, and at least one film consists predominantly of PET raw materials with a thickness of 8 to 20 μm. The overall PE content is always greater than the PET content in the laminate.

[0130] Another similar example is laminates made of PE, PET, and PP, more specifically, PET and CPP (cast PP) or PET and BO-PP (biaxially oriented PP). In this case, at least one film of the laminate consists predominantly of PP raw materials with a thickness of 10 to 200 μm, and at least one film consists predominantly of PET raw materials with a thickness of 8 to 20 μm. The total PP content is generally always greater than the PET content in the laminate.

[0131] A film web can be printed completely or partially with solvent-based or solvent-free printing inks that are thermally stable or thermally unstable above approximately 200 °C. Today, the standard for flexographic or gravure printing used in flexible packaging is often nitrocellulose-based printing inks, which form toxic gases during recycling in the extruder and lead to corrosion.

[0132] Optionally, a film web can also be coated, in particular to increase the barrier effect of the laminate.

[0133] The barrier effect of plastics can be increased through various measures. Firstly, certain additives such as EVOH (ethylene-vinyl alcohol copolymer) or PVDC (polyvinylidene chloride) can be used to improve the barrier effect of the plastic against oxygen, moisture, aromas, and flavors. Secondly, the barrier effect can be increased by applying coatings to the plastic surface. Finally, the thickness of the plastic can also play a role, as thicker plastics generally have a higher barrier effect than thinner ones. Overall, there are various ways to improve the barrier effect of plastics, depending on the specific requirements and application areas of the material.

[0134] Plastics are sometimes coated with a metallic layer to enhance certain properties or add new functionality. For example, a metallic layer can be applied to plastic to improve its electrical conductivity, allowing it to be used as an electrically conductive material. A metallic layer can also help increase the plastic's resistance to weathering and corrosion by protecting it from damage caused by moisture, UV radiation, or oxygen. Finally, a metallic layer can also be used to give the plastic a specific color or appearance, for example, to create a gold, silver, or metallic color.

[0135] The coating thickness is often less than 3 pm, usually 2 pm or less, sometimes only in the range of 3 to 50 nm ("met").

[0136] The film webs are joined using adhesives ("adh"). Today, polyurethane-based adhesives with a layer thickness of 1-4 gsm are mainly used, alternatively acrylic resin dispersion / emulsion adhesives are also used.

[0137] Or an adhesive layer (e.g. EVA) was extruded directly into one of the film strips, so that no adhesive is required when joining them ("coating").

[0138] Examples of laminates that can be used as input material are:

[0139] 1) PE / / adh / / PET

[0140] 2) PE / / adh / / ink / PET

[0141] 3) PE / / adh / / met-PET / / adh / / ink / PET

[0142] 4) coating / ink I met-PET 11 adh 11 PE

[0143] 5) PE 11 adh 11 ink / coating / PET

[0144] 6) PE 11 PET

[0145] 7) BO-PP / / adh / / PET

[0146] 8) CPP / / adh / / PET

[0147] 9) met-BO-PP / / adh / / PET

[0148] 10) met-CPP 11 adh 11 PET

[0149] Another example of waste that is currently only subject to very limited recycling is multilayer films made of PE / PA, PE / EVOH, PE / PA / EVOH, etc. Such films are colloquially referred to as barrier or high-barrier films. They are designed to minimize contact with certain environmental factors and thus extend the shelf life of packaged products. The challenge with material recycling lies in the fact that the polymers typically used (e.g. PE or PP in combination with EVOH and / or PA, etc.) are not compatible with each other. Separating the individual components (PE, PP, PA, EVOH, etc.) during the recycling process for targeted recovery is very complex and therefore unusual.Especially when such films (barrier or high-barrier films) are printed, they can only be recycled to a limited extent—in highly diluted form. Like PET / PE laminates, these films are widely available as both PIR and PCR products.

[0150] The direct processing of these wastes - without a prior treatment step - is not possible today for the reasons mentioned above (compatibility, contamination by e.g. printing ink, different processing temperatures).

[0151] Currently, non-segregated waste can only be recycled on a small scale. The proportion of waste in a new product is small; the waste is mixed with new material. The proportion of recyclate in the layer in which it is used is generally less than 30% by weight, very often less than 20% by weight. The recyclates are generally processed, meaning that the waste is not directly processed into a new product; instead, they are first processed into granules.

[0152] The problem with non-segregated waste is that it can contain plastics from waste streams originating from household plastics collections, for example, from recycling systems such as the yellow bag. Colloquially, these are referred to as medium or low-quality PCR. These materials are commercially available in large quantities as granules, and a well-known example is the plastic recyclate from the Green Dot sold under the brand name "Systalen." The composition of these recyclates varies and is not 100% known. In any case, a mixture of various plastics is present, even if these consist primarily of PE, i.e. more than 60%, preferably 80%, particularly preferably 90%, and especially preferably 95% or more PE. It should be expressly mentioned that the composition of the mixture is not limited to plastic, but also, for example,also contains various contaminants; for example, but not limited to, impurities caused by printing ink.

[0153] In contrast to non-segregated waste, waste such as transport packaging from supermarket delivery areas is also worth mentioning. These are also generally usable, as these plastics are rarely contaminated and, in the context of this application, are also considered recyclable. They usually occur in the form of stretch film or hood film, thus providing a better starting point for high-quality material recycling.

[0154] It is desirable to add 50% or more of mixed waste to at least one layer of a film, thereby significantly increasing the proportion of material recycling. In particular, it is desirable to do this by direct processing without prior processing into granules. Neither of these is currently possible.

[0155] The use of twin-screw extruders enables more efficient processing of raw materials and opens up the possibility of using up to 100% recycled material. Twin-screw extruders allow different plastics to be more effectively homogenized and integrated into the production process.

[0156] The object of the invention is to recycle such waste from the PIR and / or PCR sectors. To this end, it is proposed to use this waste as a blend in at least one layer of a new film.

[0157] The present invention is based on the object of providing an improvement or an alternative to the prior art.

[0158] According to a first aspect, the stated object is achieved by a method for producing a film having at least one layer with a polymer blend, comprising at least a first polymer and a second polymer, characterized in that at least two of the polymers involved are incompatible with one another, and in that the polymer blend is processed in an extruder.

[0159] If the film being produced has two or more layers, the two or more layers may be fed from a single extruder or fed from several separate extruders.

[0160] The layer can be a single-layer film, for example. However, it can also be a layer of a multi-layer film.

[0161] In the exemplary case of a three-layer film in which the polymer is present in the middle layer, the layer distributions can be as follows: 25% - 50% - 25%. The preferred layer distribution is 20% - 60% - 20%. The most preferred layer distribution is 15% - 70% - 15%. The most preferred layer distribution is 10% - 80% - 10%. The preferred goal is to maximize the recyclate in the respective recyclate layer. The different layer ratios allow for precise adjustment depending on the specific requirements of the application. For example, a distribution of 25% - 50% - 25% enables uniform integration of the recyclate in the middle layer, while 10% - 80% - 10% enables a focus on a maximum amount of recyclate in the inner layer.These flexible layer ratios contribute to achieving the desired material properties while ensuring efficient use of recycled material in film production.

[0162] In the exemplary case of a five-layer film, the layer distributions can be as follows: 10% - 20% - 40% - 20% - 10%. The layer distribution is preferably 15% - 10% - 50% - 10% - 15%. The layer distribution is particularly preferably 10% - 10% - 60% - 10% - 10%. The layer distribution is especially preferably 7.5% - 7.5% - 70% - 7.5% - 7.5%.

[0163] The actual proportions of the layer distribution depend largely on the desired properties of the film to be produced, especially the mechanical properties. Targeted adjustment of these properties can be achieved by controlling the proportions and / or selecting the materials, especially in the virgin material portions of the outer layers and sub-outer layers (skin and subskin layers). By varying these parameters, certain mechanical properties such as strength, flexibility, and durability can be influenced.

[0164] For example, a higher concentration of virgin material in the outer layers enables improved strength and abrasion resistance, while a higher concentration of recycled material in the middle layer can help minimize the environmental footprint. Precise adjustment of the layer composition makes it possible to produce tailor-made films with the desired performance characteristics for different applications. This flexibility in material selection and layer arrangement helps adapt film production to specific requirements while promoting sustainable practices.

[0165] The polymer blend can, of course, also be present in an outer layer and / or sub-outer layer. This allows for additional variability in film production, as the choice of layer in which the polymer blend is placed has specific effects on the final product properties.

[0166] The positioning of the polymer blend in the different layers allows for the integration of different functions into the film to meet the requirements of different applications. This approach underscores the versatility of polymer blends in film production and the ability to tailor material properties depending on the application and desired performance.

[0167] As described above, film manufacturing offers the option of producing multilayer composites with varying numbers of layers. For example, but not exclusively, 3-, 5-, 7-, and 11-layer composites can be produced. This flexibility opens up the possibility of combining a wide range of material properties and thus meeting the specific requirements of different applications. Another aspect in the production of films from recycled material is the potential odor development of the recycled material. To minimize this, barrier layers can be integrated to encapsulate the odor of the polymer blend, i.e., the recycled material. These barrier layers offer an effective solution for reducing unwanted odor emissions and improving the quality of the produced films.

[0168] Another option for odor minimization is post-treatment of the film with plasma, which modifies the film surface. This treatment can be performed both offline and inline. For example, inline treatment can be performed after the turning bar, preferably after the opening of the film tube or web, or before the winder. Alternatively, with offline treatment, the film can be unwound after winding, treated, and then rewound or used for further processing steps. This approach demonstrates the diversity of available techniques for odor minimization in film production.

[0169] In a further development of the process, the middle layer or the layers containing the polymer blend can be specifically foamed. This process can be achieved by adding chemical and / or physical blowing agents to the polymer blend. The addition of these blowing agents enables controlled foaming, where the degree of foam formation can be adjusted as required. This targeted foaming can reduce degassing, resulting in a more efficient and sustainable processing process. The precise adjustability of the degree of foaming also opens up the possibility of foregoing complete degassing, which not only optimizes the processing but also saves resources. This innovative approach thus contributes to the further development of environmentally friendly processing technologies in the recycling sector.

[0170] The targeted foaming process makes it possible to encapsulate gases within the material. During the foaming process, closed cells preferentially form within the material, trapping the contained gases. This has the advantage of effectively encapsulating the gases, reducing uncontrolled degassing, for example, at the nozzle when the material exits the die head. The closed cells act like small barriers that contain the gases within the material and thus minimize their release into the environment. This property not only contributes to improving the material's properties but can also have a positive impact on the environmental balance by reducing the release of gaseous substances during processing and use of the material.

[0171] The resulting film exhibits comparable properties to conventional films and can therefore be further processed using standard methods. These films are, for example, stretchable, meaning they can be subsequently stretched to improve specific mechanical or optical properties. The customization options are diverse. The versatility of these films thus opens up various options for post-processing and use in various industrial applications.

[0172] The films can be manufactured using various production processes, including air-cooled blown film extrusion, water-cooled blown film extrusion, cast film extrusion, or sheet extrusion. This allows for flexible adaptation of film production to specific requirements and applications.

[0173] The possible input materials that can be used as recyclate for the polymer blend are extremely diverse and consist of, for example, various types of printed and unprinted polyethylene or polypropylene films. These materials, both PIR (Post Industrial Recyclate) and PCR (Post Consumer Recyclate), are used in a wide range of applications. Typical applications for recyclable films extend across various sectors, including packaging and transport, hygiene, agriculture, the construction industry, industry, healthcare, the clothing industry, the leisure and outdoor industry, plumbing and heating installation, the automotive industry, and the electrical industry. From the packaging and transport sectors, for example, PE films for garbage bags, carrier bags, food packaging, shrink and stretch films, hoods, and liner films can be recycled.Another example is laminating film, which is used in combination with other materials. The possible applications for these films are diverse and range from industrial packaging to specialized applications in various industries. The variety of input materials for the polymer blend extends further across different types of film from various sectors: In the hygiene sector, for example, breathable PE film is used, particularly in products such as diapers. In agriculture, for example, PE films play a crucial role, be it as greenhouse covers, mulch films, silage films, or components of irrigation systems. In the construction industry, PE films are used, for example, as vapor barriers, waterproofing for foundations and sewer lines, as well as temporary construction films and geomembranes that enable permanent barriers against the penetration of liquids or gases.Films are used in many different ways in industry, including in the form of pouches, sacks for granules, powders, or liquids, and for covering pallets and barrels. In the healthcare sector, for example, films are used for medical packaging, pouches, and disposable products. In the clothing industry, they are used in the production of protective covers. Leisure and outdoor equipment benefits from films in things like tents, backpacks, waterproof bags, and sleeping mats. Films also play a role in plumbing and heating installations, particularly for pipes. The automotive industry uses films for things like car covers, seat protectors, and interior fittings. Finally, in the electronics industry, films with antistatic properties protect electronic components, while surface protection films protect against mechanical damage and often have a sticky surface.

[0174] Films that are preferably used as input material are those that are primarily used in the packaging of foodstuffs or similar, so-called barrier films. These films are often used in further processing, for example, as lidding films, in laminates or as films that are thermoformed. In addition to PE, these films very often contain other polymers that are not compatible with PE; examples of this are polymers such as PA, CoPA, PET, EVHO, PVOH, etc. The films today usually have 5, 7, 9, 11 or more layers. However, barrier films that consist of only three layers are also known. The structure of the films can be symmetrical or asymmetrical. Characteristic are the material blocks that act as neighbors to the PE (or sometimesPP) ensure the barrier function, or more precisely the arrangement of the individual materials, or more precisely the layers: Arrangements such as PE-HV-PA-HV-PE, PE-HV-EVOH-HV-PE, and PE-HV-PA-EVOH-PA-HV-PE are particularly well-known. The abbreviation "HV" stands for adhesion promoter. These are symmetrical arrangements with the barrier material(s) in the center of the film. Asymmetrical arrangements are also known, with the barrier material at least on the outside of the film composite, but also sometimes with another barrier block further towards the center of the film. Typical thicknesses range from 30 to 40 μm for lidding films up to 300 μm and even 400 μm or more for thermoforming films or so-called tube laminate films.Multilayer films with barrier materials are currently produced using state-of-the-art technology, both by air-cooled blown film extrusion and water-cooled blown film extrusion, as well as the multi-bubble process (double and triple bubble process), and also, for example, as flat film (cast film or sheet film).

[0175] Films that can be used as input material (e.g., PE film or PP film) and barrier films can be either unstretched or stretched. Examples of stretched films include biaxially stretched PE film (BO PE), biaxially stretched PP film (BO PP), biaxially stretched PA film (BO PA), monoaxially stretched P film (MDO PE), and monoaxially stretched PP film (MDO PP).

[0176] Another preferred input material for polymer blends is laminates. Such laminates can originate from both PCR and PIR film applications.

[0177] In principle, each of the potential input materials mentioned can also be produced as a film with a recycled material, i.e. one or more or even all layers can contain a polymer blend.

[0178] Recycling material, ie in particular a polymer blend, can be used in all known film applications; ie in principle, each of the films previously mentioned as potential input material can be manufactured with a recycling material, i.e. one or more or all layers of these films can comprise a polymer blend.

[0179] Depending on legal requirements and the quality of the PIR and / or PCR, there may be restrictions on their use. The following are examples of particularly preferred applications, but are not exhaustive:

[0180] • Garbage bags

[0181] • Shipping bags

[0182] • Construction film

[0183] • Covers

[0184] • Liners

[0185] • Collation Shrink

[0186] • Outer packaging

[0187] • Press packaging

[0188] • Bags and sacks (“heavy goods bag”)

[0189] • Shrink hoods

[0190] • Stretch hoods

[0191] • Mulch film

[0192] • Silage films

[0193] • Greenhouse covers

[0194] • Geomembran

[0195] • Laminating film

[0196] • Symmetrical barrier film

[0197] • Asymmetric barrier film

[0198] A polymer blend is typically a material consisting of two or more polymers blended together. The different polymers can have different properties, which can improve the material as a whole. For example, a polymer blend can be made from a hard polymer and an elastic polymer to create a material with high strength and good extensibility. Polymer blends are often used in the plastics industry to create materials with specific properties. They can also be used to improve the performance of materials and increase their resistance to aging. Polymer blends are also used in other fields such as medical technology and the construction industry. Furthermore, the polymer blend can be designed according to the definition described in the prior art.

[0199] A polymer is typically a large organic molecule made up of many smaller molecules called monomers. Polymers occur in many different forms and are widely used in nature and in synthetic chemistry. They are the basic building blocks of materials such as plastics, elastomers, and textile fibers. There are two main classes of polymers: thermoplastics and thermosets. Thermoplastics are polymers that become soft and malleable at elevated temperatures but solidify again at room temperature. They are often used in the manufacture of plastics. Thermosets, on the other hand, are polymers that remain hard and dimensionally stable at elevated temperatures. They are often used in the manufacture of paints and adhesives. In this case, the preferred type is thermoplastics.

[0200] The compatibility of polymers in this case corresponds to the definition described above in the state of the art.

[0201] Description: Shearing entry, generated or further processed

[0202] The extruder preferably introduces a shear input into the polymer blend.

[0203] The shear input is measured in units such as Pascal (Pa) or bar and indicates how much pressure is required to drive a material through an extruder nozzle.

[0204] The shear force of an extruder depends on various factors, such as the nozzle shape, nozzle size, and viscosity of the material being extruded. An extruder with a high shear force can more easily process materials with high viscosity and high strength and force them through the nozzle.

[0205] The shear load of an extruder plays a crucial role in the manufacture of plastic products, especially in the extrusion of materials such as polymer blends and compounds. A high shear load enables materials to be processed and formed with high quality and precision. A low shear load, on the other hand, can lead to contamination, warping, and other quality issues.

[0206] The following terminology is used to explain this:

[0207] It should be expressly pointed out that, within the scope of this patent application, indefinite articles and indefinite numerical expressions such as "one...", "two...", etc., are generally to be understood as "at least one...", "at least two...", etc., unless the context or the specific text of a particular passage indicates that only "exactly one...", "exactly two...", etc., are intended. Furthermore, all numerical expressions as well as information regarding process parameters and / or device parameters are to be understood in the technical sense, i.e., subject to the usual tolerances. Even the explicit specification of the restriction "at least" or "at least" or similar does not imply that the simple use of "one," i.e., without specifying "at least" or similar, means "exactly one."

[0208] The terms listed here should always be defined and explained in more detail by means of the explanations of the state of the art.

[0209] In a further development of the process, the polymer blend has at least two glass transition temperatures.

[0210] The glass transition temperature is typically the temperature at which a material changes from a solid to a liquid state. Glass transition temperatures are specific temperatures at which the material changes from an amorphous to a crystalline state.

[0211] The glass transition temperature of a material depends on various factors, such as its composition, structure, and viscosity. The glass transition temperature can be determined by measuring the material's heat capacity, for example, using differential scanning calorimetry (DSC).

[0212] The glass transition temperature plays an important role in the processing of materials, especially in the production of plastics. A material with a low glass transition temperature can be processed at lower temperatures. A material with a high glass transition temperature, on the other hand, requires higher temperatures to melt.

[0213] Typically, each polymer has a single glass transition temperature. The transition temperatures of the individual polymers are preferably different from one another, so that their characteristic glass transition temperature can be detected in the polymer blend. Depending on the quality of the individual polymers, the glass transition temperature can also be a temperature range. Therefore, it is preferable to expect at least as many glass transition temperatures in the polymer blend as there are different characteristic glass transition temperatures of the individual incompatible polymers.

[0214] In a further development of the process, the polymer blend has at least two ranges of characteristic melting temperatures.

[0215] The melting temperature, also called the melting point, is typically the temperature at which a material changes from a solid to a liquid state. The melting point of a material depends on various factors, such as its composition, structure, and viscosity. The melting point can be determined by measuring the material's heat capacity, for example, using differential scanning calorimetry (DSC). It can also be determined by directly heating the material in a furnace or by applying laser radiation.

[0216] Melting temperature plays an important role in material processing, especially in the production of plastics. A material with a low melting temperature can be processed at lower temperatures. A material with a high melting temperature, on the other hand, requires higher temperatures to melt.

[0217] Typically, each polymer has a single melting temperature. Preferably, the melting temperatures of the individual polymers are different from each other, so that their characteristic melting temperature can be detected in the polymer blend. Depending on the quality of the individual polymers, the melting temperature can also be a temperature range. Therefore, it is preferable to have at least as many melting temperatures in the

[0218] Polymer blend, as different characteristic melting temperatures of the individual incompatible polymers are to be expected.

[0219] In a further development of the method, the extruder has mixing elements which apply a shear input to the polymer blend and / or the first polymer and the second polymer in order to mix and / or homogenize the polymer blend and / or the first polymer and the second polymer.

[0220] The mixing elements are arranged, for example, at the end of the extruder to build up pressure to convey the polymer blend out of the extruder and out of the die. However, the mixing elements can also be arranged at the beginning of the extruder or along the extruder section to thoroughly mix the polymer blend or its precursors. The polymer blend is usually described here as comprising two mutually incompatible polymers. However, the polymer blend can also be a mixture of more than two polymers.

[0221] Preferably it is a polymer blend of 2 to 5 polymers.

[0222] In a further development of the method, the extruder is designed as a single-screw extruder which applies a shear input to the polymer blend and / or the first polymer and the second polymer in order to mix and / or homogenize the polymer blend and / or the first polymer and the second polymer.

[0223] A single-screw extruder consists of a barrel containing a spiral screw, also known as a flight or a screw. The screw is driven and propels the material through a nozzle of the extruder.

[0224] A single-screw extruder offers many advantages over other extruder types. It enables even material distribution, high processing speed, and high-quality end products. It can also be easily adapted to the requirements of different materials and applications.

[0225] A single-screw extruder is often used in the plastics industry, especially in the production of plastic profiles, films and sheets.

[0226] In a further development of the method, the extruder is designed as a twin-screw extruder which applies a shearing action to the polymer blend and / or the first polymer and the second polymer in order to mix and / or homogenize the polymer blend and / or the first polymer and the second polymer.

[0227] A twin-screw extruder is similar in design to a single-screw extruder. However, it consists of two screws that drive the material through the extruder's nozzle. The screws can, for example, rotate in opposite directions. The extruder is primarily used to melt and homogenize the recycled material into a melt and has a melt stream.

[0228] The twin-screw extruder is a multi-screw extruder. In plastics technology, it is used for processing and shaping plastic melts. In this case, the recycled material or a mixture containing recycled material is conveyed through a heated cylinder by two rotating, intermeshing screw shafts, where it is melted.

[0229] Twin-screw extruders are typically classified based on the centerline distance between the two screw shafts and their direction of rotation: tangential or closely meshing co-rotating twin-screw extruders, or tangential or closely meshing counter-rotating twin-screw extruders. The counter-rotating twin-screw extruder imposes less shear on the material being extruded and therefore places less stress on it. The counter-rotating twin-screw extruder is therefore preferred for processing temperature-sensitive materials. In this case, the co-rotating twin-screw extruder, especially the closely meshing co-rotating twin-screw extruder, is particularly preferred.

[0230] The twin-screw extruder offers particularly good mixing performance, allowing the used plastic to be recycled. Recycling and / or mixing in additives is particularly advantageous with a twin-screw extruder.

[0231] According to one embodiment, the blown film system has a filter with at least one filter element for filtering the melt from an unfiltered side to a filtered side. The filter serves as a dirt trap. The filter is preferably a filter from the group consisting of melt filters, extruder screens, filter discs, and strainer screens. The filter element can be single-layer, multi-layer, or pleated. The filter element can comprise a metal wire mesh, metal fiber fleece, and / or sintered fabric laminate.

[0232] The filter is preferably arranged in the melt stream between the extruder and the ring die. The filter can also be part of the extruder. The filter is preferably arranged between the extruder and the ring die melt pump.

[0233] According to one embodiment, the twin-screw extruder has at least one venting unit, which enables the extraction of impurities and contaminants. The venting unit can be designed as a venting zone as part of the extruder. The venting unit can be used to remove volatile components from the melt. To improve venting, it is preferred that the fill level in the twin-screw extruder be below 100%; in particular, it is preferred that the fill level be below 80%. Such a fill level is preferred because otherwise the melt would be forced into venting nozzles and escape from the venting unit.

[0234] According to one embodiment, the twin-screw extruder has at least one venting unit designed as an atmospheric venting unit. With this design, the volatile components can be released from the venting unit without applying a negative pressure.

[0235] According to one embodiment, the twin-screw extruder has at least one degassing unit designed as a vacuum degassing unit. In this embodiment, a vacuum is applied to the degassing unit. The vacuum can be generated by a vacuum pump. This design enables particularly thorough degassing of volatile components. It is preferred that the degassing unit, in particular the vacuum degassing unit, has a means for collecting the volatile components, preferably in the form of condensate.

[0236] In a further development of the process, entraining agents can be used. The use of entraining agents represents an effective method for increasing degassing performance during the processing of recyclate. Entraining agents are special substances that can be introduced into the polymer blend of the recyclate to promote the release of gases during processing in the extruder. These substances influence the degassing properties of the recyclate, typically by reducing surface tension and thus promoting gas bubble formation. This leads to improved diffusion of gases from the recyclate and enables more efficient degassing. The selection of the appropriate entraining agent depends on the specific requirements of the process and the desired material properties.The targeted integration of entraining agents into the manufacturing process helps to optimize the quality of the final product while making the processing more efficient.

[0237] According to one embodiment, the extruder has a recycling material feed with a stuffing screw. The stuffing screw allows the recycling material to be fed particularly evenly into the extruder. The recycling material feed preferably has a hopper in which the stuffing screw is arranged. The stuffing screw is preferably driven by a drive independent of the extruder.

[0238] According to one embodiment, the blown film system has at least two pressure sensors for detecting pressures within the melt flow guide, preferably in the melt flow guide at the extruder and in front of the ring die. The pressure sensors are designed to detect the melt pressure in the melt flow during operation of the blown film system.

[0239] According to one embodiment, the blown film line has at least two pressure sensors for detecting the melt pressure in the melt stream, one at the extruder and one upstream of the ring die. The first pressure sensor is preferably arranged directly at the extruder or beyond the extruder. The second pressure sensor is preferably arranged directly upstream of the ring die or at the ring die. In an alternative embodiment, the second pressure sensor is arranged upstream of the ring die melt pump. The extruder and / or the ring die melt pump and / or the recycling material feed can preferably be regulated depending on the melt pressure in the melt stream, which is detected by the first and / or second pressure sensor at the extruder and / or upstream of the ring die.

[0240] According to one embodiment, the blown film system has two additional pressure sensors for measuring the melt pressure in the melt stream before and after the filter. These additional pressure sensors are therefore pressure sensors that are present in addition to the pressure sensors mentioned above. These additional pressure sensors can be installed directly before and after the filter. However, it is preferred that the additional pressure sensors be positioned immediately before the filter and immediately before the ring die. In this configuration, the second pressure sensor is preferably positioned immediately after the filter.

[0241] According to one embodiment, the filter has a cleaning device that continuously and / or discontinuously renews the filter element. In this context, the term "renewed" refers to both the cleaning of a filter element and the insertion of a new filter element that was not previously used as a filter element or was cleaned before reuse. This insertion can be done manually or, preferably, automatically.

[0242] In a further development of the process, the extruder is designed as a twin-screw extruder with co-rotating screws. In this design, both screws run in the same direction.

[0243] In a further development of the method, the extruder is designed as a planetary roller extruder, which applies a shear input to the polymer blend and / or the first polymer and the second polymer in order to mix and / or homogenize the polymer blend and / or the first polymer and the second polymer.

[0244] A planetary roller extruder typically comprises a driven central spindle on which several individual planetary spindles, variable in number, roll. The rotating planetary spindles are usually additionally guided by an internally toothed bushing (roller cylinder). This movement propels the material through the extruder's nozzle.

[0245] In a further development of the process, additives are added to the polymer blend and / or the first polymer and the second polymer to improve miscibility.

[0246] Additives are typically materials or additives that are added to another material to improve or change its properties. Additives are often used in the plastics industry to modify materials such as polymers, elastomers, polymer blends, and compounds, adapting their properties to the requirements of their final products.

[0247] Additives can have various functions, such as improving strength, hardness, elasticity, resistance to chemicals and temperatures, aging resistance, and color. They can also be used to make materials easier to process or to change their optical properties.

[0248] They can be added in the form of powders, liquids or pastes and must be carefully selected to achieve the desired properties.

[0249] To reduce potential odor nuisance during the processing of polymers for the polymer blend, specific odorants can be added. These additives serve to mask or neutralize odors that could arise during the recycling process. The selection of odorants is preferably aimed at ensuring a pleasant and acceptable environment during processing without compromising the quality of the final product.

[0250] Stabilizers, such as antioxidants, can be incorporated into the manufacturing process of polymer blends. These stabilizers help reduce the formation of defects and particles in the material. The addition of antioxidants preferentially slows down the degradation of the polymer due to oxidative stress, which can improve the stability and quality of the polymer blend. This helps preserve the mechanical and chemical properties of the material and thus optimize the performance of the recycled product.

[0251] There are a variety of options for additives to influence the mixing effect. For example, when processing recycled polymer blends, the addition of low-viscosity materials can be used specifically to influence and / or improve the mixing effect and thus achieve a more homogeneous—i.e., better mixed—melt (better phase distribution). In this case, materials with a Melt Flow Index (MFI) of 1, and preferably 2 or higher, are used for admixture. The MFI provides information about the flowability of the molten material and thus influences the processing properties during production.

[0252] The viscosities of the polymer blend components can be regulated, for example, by adding virgin material to the manufacturing process. For example, higher-viscosity materials can be blended to improve bubble stability during production on a blown film line. Typically, materials with an MFI value of 1, preferably 0.7, and particularly preferably 0.3 or less are used. Precise viscosity adjustment contributes to optimizing the processing properties of the polymer blend and increasing the quality of the produced films, particularly with regard to bubble stability and final product quality.

[0253] In a further development of the process, compatibilizers are added to the polymer blend and / or the first polymer and the second polymer to improve miscibility.

[0254] The compatibilizers are preferably constructed according to the compatibilizers described in the prior art. In a further development of the process, the compatibilizer is a polymer, a block copolymer, or a graft copolymer.

[0255] A block polymer is typically a polymer composed of two or more different monomers, usually arranged at regular intervals in the polymer chain. Block polymers are usually produced by combining two or more polymers that have different properties.

[0256] The properties of a block polymer depend primarily on the type and arrangement of the monomers and the length of the block segments. Block polymers can have hard and soft regions and can exist in various states of aggregation, such as amorphous and crystalline regions.

[0257] Block polymers are widely used in the plastics industry to create materials with specific properties. They can also be used to improve the performance of materials and increase their resistance to aging.

[0258] The production of block polymers requires specialized processes, such as polymer-polymer coupling or block polymerization. The properties of block polymers can be precisely controlled by selecting the monomers and block lengths to obtain materials with the desired properties.

[0259] Block polymers can be used as additives in polymer blends and compounds to improve the properties of these materials.

[0260] Graft copolymerization is typically a technique for producing polymers whose main chain serves as the starting point for further chains of a different monomer type. This creates a copolymer whose main chain is usually joined in a comb-like manner by chains of another monomer type. This offers another possibility for developing plastics with new, defined properties. A graft polymer is preferably a material consisting of polymers and produced by a grafting process. In the grafting process, for example, two or more polymers are bonded together to create a new material with improved properties. This can be used in plastics engineering to produce materials with specific properties such as high strength or low water absorption.

[0261] In a further development of the process, the compatibilizer is an EVA polymer or an ionomer polymer.

[0262] The EVA polymer is preferably an ethylene-vinyl acetate copolymer, which is typically made from ethylene and vinyl acetate. It is preferably a flexible material. EVA preferably results in increased flexibility, elasticity, and chemical resistance.

[0263] Ionomer polymers are preferably polymers that contain ionic bonds and are therefore electrically conductive. They are typically produced by combining polymers with metal ions and are usually characterized by their high strength, chemical resistance, and electrical conductivity.

[0264] In a further development of the process, a compound with a reactive group is grafted onto the first polymer and / or the second polymer to improve miscibility.

[0265] In a further development of the process, the reactive group is an epoxy group, which is preferably introduced by reaction of the polymer with glycidyl methacrylate (GMA).

[0266] In chemistry, the epoxy group usually refers to a structure consisting of one carbon atom bonded to two oxygen atoms. This structure is often found in epoxy compounds produced by the reaction of phenols and epoxy oils. Epoxy groups are usually very reactive and can react with various other chemicals such as amines or polyols to create new compounds with different properties. Glycidyl methacrylate (GMA) is a monomer produced, for example, by the reaction of methacrylic acid with epichlorohydrin. It belongs to the class of epoxidized methacrylates and is an important starting material in the production of epoxy resins and other epoxy compounds. GMA is usually characterized by its high reactivity and its ability to improve the properties of polymers, for example, by increasing their chemical resistance and / or hardness.It is preferably used in various areas of the plastics industry, for example in the production of coatings.

[0267] In a further development of the process, the reactive group is an anhydride group, which is preferably introduced by reaction of the polymer with maleic anhydride (MA).

[0268] In chemistry, the anhydride group typically refers to a special structure consisting of a carbon atom bonded to two oxygen atoms. It is formed, for example, when an acid is stripped of its water molecules and can be generated by heating or treatment with solvents. Anhydrides are typically highly reactive compounds and can react with various chemicals such as alcohols or amines to form new compounds. They are often used in the plastics industry, for example, as reaction accelerators.

[0269] Maleic anhydride (MA) is an anhydride produced, for example, by heating maleic acid. It belongs to the class of dicarboxylic acids and is typically characterized by its high reactivity and its ability to improve the properties of polymers. MA is widely used in the plastics industry, for example, as a reaction accelerator in the production of polyester resins or as a crosslinking agent in the production of polyurethanes. It can also be used as a plasticizer in PVC plastics.

[0270] In a further development of the process, the polymer blend predominantly comprises two types of plastic. These two types of plastic preferably make up the largest amount of the material.

[0271] In a further development of the process, the first polymer is a polyolefin or a polymer blend of several different polyolefins.

[0272] Polyolefins are a class of polymers typically made from olefins. Olefins are usually organic compounds containing a double bond between two carbon atoms. Examples of olefins are ethylene and propylene. Polyolefins are typically produced by polymerizing olefins and are usually characterized by their high strength, chemical resistance, and weather resistance.

[0273] In a further development of the process, the first polymer is a polyethylene or a polymer blend of several different polyethylenes.

[0274] Polyethylene (PE) is a polymer typically made from ethylene. It belongs to the class of polyolefins and is one of the most widely produced polymers in the world. PE is characterized by its high strength, chemical resistance, and weather resistance. It is used, for example, in the production of films, foams, pipes, and cable insulation.

[0275] In a further development of the process, the first polymer is a polypropylene or a polymer blend of several different polypropylenes.

[0276] Polypropylene (PP) is a thermoplastic, usually produced by chain polymerization of propylene. It belongs to the polyolefin group, is semi-crystalline, and non-polar. Its properties are similar to polyethylene, but it is generally somewhat harder and more heat-resistant.

[0277] In a further development of the process, the second and a possibly present third polymer are barrier polymers. The barrier polymer is preferably from the group consisting of EVOH, PA, PET, PE, PP, and PVC. Strictly speaking, PET, PE, and PP are not classic barrier polymers.

[0278] A barrier polymer is a type of polymer that typically provides a barrier to the movement of molecules or ions through it. Barrier polymers are used in many applications, such as food packaging. They are often made from materials such as polyethylene, polypropylene, or polyethylene terephthalate (PET), which are known for their durability and chemical and moisture resistance. The specific properties of a barrier polymer depend on its chemical structure and the type of molecules it is designed to block.

[0279] EVOH, PA, PET, PE, PP, and PVC are each different types of plastics. Here's a brief overview of each:

[0280] EVOH, or ethylene vinyl alcohol, is a copolymer often used as a barrier material in packaging applications. It is known for its high oxygen and moisture barrier properties, making it useful for preserving the freshness of food and other perishable products.

[0281] PA, or polyamide, is a type of polymer also known as nylon. It is typically a strong, durable material used in a wide variety of applications.

[0282] PET (polyethylene terephthalate) is a polymer commonly used to make plastic bottles, packaging materials, and other products. It is typically known for its strength and barrier properties, making it a good choice for packaging applications.

[0283] PE, or polyethylene, is a plastic used in a wide variety of applications, including food packaging, bottles, and medical devices. It is typically known for its flexibility, chemical resistance, and durability.

[0284] PP, or polypropylene, is a plastic widely used in a variety of applications, such as food containers, packaging materials, and automotive parts. It is typically known for its durability, light weight, and resistance to chemicals and heat.

[0285] PVC (polyvinyl chloride) is a plastic commonly used in a variety of applications, such as pipes, cables, and flooring. It is typically known for its durability, flexibility, and chemical resistance.

[0286] In a further development of the process, the second polymer is an EVOH or a polymer blend of several different EVOHs.

[0287] In a further development of the process, the second polymer is a PA, preferably a PA6 / 6.6 copolyamide or polyamide 6, or a polymer blend of several PAs.

[0288] In a further development of the process, the PA content in the polymer blend is less than 50 wt.%, preferably the PA content is less than 35 wt.% and particularly preferably the PA content is less than 25 wt.%.

[0289] Virgin material may also be added to the polymer blend. For example, polyolefin, preferably polyethylene, may be added as virgin material. The amount of virgin material can vary depending on the quality of the input material of the polymer blend or the proportion of foreign matter in the polymer blend.

[0290] Typically, virgin material consists primarily of polyethylene. In a further development of the process, the second polymer is PET or a polymer blend of several different PETs.

[0291] In a further development of the process, the PET content in the polymer blend is less than 2.5 to 50 wt.%, preferably the PET content in the polymer blend is 3.5 to 37.5 wt.% and particularly preferably the PET content in the polymer blend is 4.5 to 25 wt.%.

[0292] In a further development of the process, the first polymer and / or the second polymer is subjected to a processing step before processing in the extruder.

[0293] In plastics engineering, processing steps generally refer to the various processes used to produce polymers. These steps include, for example, the pretreatment and processing of raw materials, polymerization (the joining of smaller molecules into larger polymers), shaping of the polymers, and subsequent post-treatment of the resulting plastics. The goal of these processing steps is usually to improve the properties and quality of the polymers and make them suitable for their intended applications.

[0294] In a further development of the process, the first polymer and / or the second polymer are present as granules before processing in the extruder.

[0295] In this example, the first polymer and / or the second polymer may have undergone a targeted processing step to ensure that they are already present in the form of a blend in granular form. This upstream processing makes it possible to combine the different polymer components into a homogeneous mixture in the form of granules. This means that the polymers are not present individually, but preferably already as a harmonized blend. These prefabricated granules offer numerous advantages in further processing, as they enable improved handling and dosing during the manufacturing process. Targeted processing in the form of granules therefore not only facilitates the processing step but can also help increase the efficiency and consistency in the production of recycled polymers.

[0296] The advantage of the first polymer and / or the second polymer already being in granular form is that it allows for better degassing. Another advantage, for example, is that smoother melting is possible. Using granules of the first polymer and / or the second polymer in the manufacturing process allows for smoother melting during the process. This leads to improved temperature control and enables precise adjustment of the melt temperature. The term "smooth melting" refers to a process in which heating to a molten phase occurs with a controlled and gradual increase in temperature. This occurs without abrupt or rapid increases in temperature to minimize potential thermal stress.The goal is to preserve the material's structure and properties as much as possible during the melting process while ensuring the desired processing properties. The use of polymer granules thus helps minimize potential thermal stress and enables efficient melt homogenization. This aspect not only promotes optimal processing of the materials but also contributes to maintaining the structural integrity of the produced film, which is particularly important with regard to quality standards and material service life.

[0297] The upstream processing of the polymer blend can take place, for example, in a single-screw extruder or a twin-screw extruder. These extruders are used to melt, mix, and homogenize the polymer blend. A single-screw extruder consists of a single rotating screw, while a twin-screw extruder has two parallel rotating screws. Both extruder types offer the possibility of efficiently processing the polymer blend and forming it into the desired shape.

[0298] In addition, the treatment can be carried out with or without degassing.

[0299] During degassing, gases that are generated during the melting process—or more precisely, those that escape, or rather, enter the gas phase—are removed from the material, such as low-molecular-weight impurities. This is important for improving the quality of the final product and minimizing potential defects. The decision to degas during processing depends on the specific requirements of the recycling process and the desired material properties.

[0300] The polymer blend, or at least one of its polymers, can be subjected to pre-filtration during the processing step. This can be advantageous for reducing machine complexity. This pre-filtration makes it possible to simplify the machine design, use more cost-effective filters, and / or require fewer filter changes. In this case, for example, a screen changer with backflushing can be dispensed with. This pre-filtration contributes to reducing the formation of specks in the final product, as larger contaminants are removed before the upstream processing step.

[0301] A further advantage of prefabricated granules is that, in some cases, the use of a second melt pump may be eliminated. This not only optimizes the efficiency of the recycling process but can also lead to cost savings and an overall simplified plant configuration.

[0302] A further advantage of the processing step is that the polymer blend can be degassed during processing. This not only contributes to increasing the overall degassing performance but also enables the reduction of odor nuisances during the actual processing. Two-stage degassing—during the preparation and during the actual processing—can increase the recycled content. Granule production with degassing during the processing thus acts as a type of pre-degassing. The processing step also enables the processing of fluff into granules. This processing step facilitates the blending of a wide variety of material streams and makes it easier to compensate for batch fluctuations. It is possible to blend smaller material streams, thereby increasing the versatility of recyclate processing.The granulate resulting from the processing step melts more evenly and faster than fluff, which is added to the process without a processing step.

[0303] The use of pellets from the preparation step offers advantages during processing in the twin-screw extruder. This enables gentler processing of the polymer blend, can extend the venting range of the screw, and contributes to reducing potential temperature peaks. This, in turn, preferably leads to fewer specks, reduces unmelted portions in the polymer blend, and improves melting behavior. The pellets from the preparation step preferably contribute to more uniform process control, which can be reflected in stable extrusion pressures and uniform temperatures throughout the entire processing process.

[0304] In a further development of the method, the first polymer and / or the second polymer is processed directly in the extruder without a preparation step prior to processing.

[0305] These can therefore be polymers directly from production or processing waste and / or polymers that have already been used by end consumers.

[0306] In this context, it is not absolutely necessary for the polymers to be in granular form. The polymers can, for example, be present as shredded packaging parts from the two sources mentioned above.

[0307] The raw materials for the production of polymer blends from shredded packaging parts can be extremely diverse and come in a variety of forms. These can be flakes, fluff, or even powder resulting from shredding, for example, or in raw material form.

[0308] The raw materials can be in various states, including web materials, blends of web materials, and / or granules. These materials can contain both virgin materials and already recycled plastics (PCR - post-consumer recyclates, PIR - post-industrial recyclates).

[0309] Furthermore, the raw materials can already be processed. These can include, for example, shredded material, granulate mixtures, powders, fillers, or even empty, but already used or unused packaging. This variety of possible raw materials provides a flexible basis for the production of polymer blends and allows for the targeted influence of the properties of the final product. The integration of different raw materials enables sustainable and resource-efficient processing of plastic waste.

[0310] In a further development of the process, the first polymer and / or the second polymer is present as production or processing waste.

[0311] Production or processing waste may contain additives from the group of process materials, virgin materials, and other materials. The other materials can be any other polymers.

[0312] In a further development of the method, the first polymer and / or the second polymer are present as a laminate. The laminate preferably comprises two to five layers, but the laminate can also be more than five-layer laminates, for example, eleven-layer laminates.

[0313] The laminate can be added as a glued-together film, or individual films can be added, e.g., the PET film before it is glued to a PE film. In other words, the laminate can be a precursor to a laminate. Precursors to a laminate are, for example, still separate layers that are not yet bonded to one another. In a further development of the method, the first polymer and / or the second polymer is / or are in the form of a laminate; preferably, at least two layers of the laminate are bonded together with a polyurethane-based adhesive having a layer thickness of 1 to 4 gsm.

[0314] Polyurethane-based adhesives are typically made from polyurethane. Polyurethane is a synthetic polymer typically made from isocyanates and polyols. These adhesives generally have high adhesive strength and are therefore often suitable for bonding dissimilar materials. They are generally elastic and can therefore be applied to materials with different expansion coefficients without breaking the bond. Polyurethane-based adhesives are commonly available in various forms, such as spray adhesives, liquid adhesives, or adhesive pads.

[0315] There are several methods for measuring the thickness of films in the range of 1 to 4 gsm (grams per square meter). One option is to use a film thickness gauge designed for measuring films. These devices usually use electromagnetic waves to determine the thickness of the film. Another option is to use a micrometer to measure the thickness of the film directly. In this case, the film is placed between two contact surfaces of the micrometer, and the thickness is measured based on the movement of the contact surfaces. It is important that the film is smooth and flat for the measurement to be accurate.

[0316] In a further development of the method, the first polymer and / or the second polymer are present as a laminate. At least two layers of the laminate are preferably bonded together with an acrylic resin dispersion / emulsion adhesive. The adhesive preferably has a layer thickness of 1 to 4 gsm.

[0317] Acrylic resin dispersion or emulsion adhesives are typically made from acrylic resin. The acrylic resin is usually dissolved in water or another solvent in the form of small particles to create a homogeneous dispersion or emulsion. These adhesives usually have very strong adhesion and good aging resistance.

[0318] In a further development of the method, the first polymer and / or the second polymer are present as a laminate. Preferably, at least one layer of the laminate is printed.

[0319] A film web can be fully or partially printed. The printing inks can be solvent-based or solvent-free. The printing inks are preferably thermally stable or thermally unstable above 200°C.

[0320] According to a second aspect, the stated object is achieved by a method for producing a film by extrusion with at least one layer with a polymer blend, which is processed according to the manner described above.

[0321] According to a third aspect, the stated object is achieved by a method for producing a film by means of blown film extrusion, flat film extrusion in the cast process or flat film extrusion in the sheet process, with at least one layer with a polymer blend, characterized in that the polymer blend is processed according to one of claims 1 to 33.

[0322] According to a fourth aspect, the stated object is achieved by a method for producing a granulate for producing a film by extrusion, characterized in that the granulate has a polymer blend with at least a first polymer and a second polymer, and that at least two of the polymers involved are incompatible with one another.

[0323] In a further development of the process, the polymer blend has at least two glass transition temperatures. The glass transition temperatures have already been defined and described above.

[0324] In a further development of the process, the polymer blend has at least two ranges of characteristic melting temperatures.

[0325] The melting temperatures have already been defined and described above.

[0326] According to a fifth aspect, the stated object is achieved by a film having at least one layer with a polymer blend comprising at least a first polymer and a second polymer, characterized in that at least two of the polymers involved are incompatible with one another.

[0327] The compatibility of polymers has already been defined and described above.

[0328] In a further development of the film, the polymer blend has at least two glass transition temperatures.

[0329] The glass transition temperatures have already been defined and described above.

[0330] In a further development of the film, the polymer blend has at least two melting temperatures.

[0331] The melting temperatures have already been defined and described above.

[0332] In a further development of the film, the film is manufactured according to the manner described.

[0333] According to a sixth aspect, the task solves a

[0334] Plastics molding plant, in particular blown film plant, flat film plant for cast processes or flat film plant for sheet processes, for producing a film with at least one layer with a polymer blend, comprising at least a first polymer and a second polymer, characterized in that at least two of the polymers involved are incompatible with one another.

[0335] In a further development of the plastic molding system, the polymer blend has at least two glass transition temperatures.

[0336] The glass transition temperatures have already been defined and described above.

[0337] In a further development of the plastic molding system, the polymer blend has at least two melting temperatures.

[0338] The melting temperatures have already been defined and described above.

[0339] In a further development of the plastic forming system, the film is produced according to one of the described types.

[0340] The embodiments shown here are merely examples of the present invention and should therefore not be considered limiting. Alternative embodiments contemplated by those skilled in the art are equally encompassed within the scope of the present invention.

Claims

Claims Process for producing a film with at least one layer with a polymer blend, comprising at least a first polymer and a second polymer, characterized in that a. at least two of the polymers involved are incompatible with one another, and b. that the polymer blend is processed in an extruder. Process according to claim 1, characterized in that a. the polymer blend has at least two glass transition temperatures. Process according to one of claims 1 or 2, characterized in that a. the polymer blend has at least two ranges of characteristic melting temperatures. Process according to one of the preceding claims, characterized in that a. the extruder has mixing elements which introduce a shear input onto the polymer blend and / or the first polymer and the second polymer in order to mix and / or homogenize the polymer blend and / or the first polymer and the second polymer.Method according to one of the preceding claims, characterized in that a. the extruder is designed as a single-screw extruder which introduces a shear input onto the polymer blend and / or the first polymer and the second polymer in order to mix and / or homogenize the polymer blend and / or the first polymer and the second polymer.

6. The method according to any one of the preceding claims, characterized in that a. the extruder is designed as a twin-screw extruder which applies a shearing action to the polymer blend and / or the first polymer and the second polymer in order to mix and / or homogenize the polymer blend and / or the first polymer and the second polymer.

7. A process according to claim 6, characterized in that a. the extruder is designed as a twin-screw extruder with co-rotating screws.

8. Method according to one of the preceding claims, characterized in that a. the extruder is designed as a planetary roller extruder which applies a shear input to the polymer blend and / or the first polymer and the second polymer in order to mix and / or homogenize the polymer blend and / or the first polymer and the second polymer.

9. Process according to one of the preceding claims, characterized in that a. additives are added to the polymer blend and / or the first polymer and the second polymer to improve miscibility.

10. Process according to one of the preceding claims, characterized in that a. compatibilizers are added to the polymer blend and / or the first polymer and the second polymer to improve miscibility.

11. Method according to claim 10, characterized in that the compatibilizer is a polymer, block or graft copolymer.

12. Process according to claim 10 and 11, characterized in that the compatibilizer is an EVA polymer or an ionomer polymer.

13. Process according to one of the preceding claims, characterized in that a. to improve miscibility, a compound having a reactive group is grafted onto the first polymer and / or the second polymer.

14. The method according to claim 13, characterized in that the reactive group is an epoxy group, which is preferably introduced by reaction of the polymer with glycidyl methacrylate (GMA).

15. Process according to one of claims 13 and 14, characterized in that the reactive group is an anhydride group, which is preferably introduced by reaction of the polymer with maleic anhydride (MA) 16. Process according to one of the preceding claims, characterized in that a. the polymer blend predominantly comprises two types of plastic.

17. Process according to one of the preceding claims, characterized in that a. the first polymer is a polyolefin or a polymer blend of several different polyolefins.

18. Method according to one of the preceding claims, characterized in that a. the first polymer is a polyethylene or a polymer blend of several different polyethylenes.

19. Process according to one of the preceding claims, characterized in that a. the first polymer is a polypropylene or a polymer blend of several different polypropylenes.

20. Process according to one of the preceding claims, characterized in that a. the second and a possibly present third polymer is a barrier polymer, preferably from the group consisting of EVOH, PA, PET, PE, PP and PVC.

21. A process according to any one of the preceding claims, characterized in that a. the second polymer is an EVOH or a polymer blend of several different EVOHs.

22. Process according to one of the preceding claims, characterized in that a. the second polymer is a PA, preferably a PA6 / 6.6 copolyamide or polyamide 6, or a polymer blend of several PAs.

23. Process according to one of the preceding claims, characterized in that a. the PA content in the polymer blend is less than 50% by weight, preferably the PA content in the polymer blend is less than 35% by weight and particularly preferably the PA content in the polymer blend is less than 25% by weight.

24. Process according to one of the preceding claims, characterized in that a. the second polymer is a PET or a polymer blend of several different PETs.

25. Process according to one of the preceding claims, characterized in that a. the PET content in the polymer blend is less than 2.5 to 50 wt.%, preferably the PET content in the polymer blend is 3.5 to 37.5 wt.% and particularly preferably the PET content in the polymer blend is 4.5 to 25 wt.%.

26. A process according to any one of the preceding claims, characterized in that a. the first polymer and / or the second polymer are subjected to a preparation step prior to processing in the extruder.

27. A process according to claim 26, characterized in that a. the first polymer and / or the second polymer are present as granules prior to processing in the extruder.

28. The method according to claim 27, characterized in that a. the first polymer and the second polymer are in the form of a blend before processing in the extruder, preferably the first polymer and the second polymer are in the form of a harmonized blend mixture.

29. A process according to any one of the preceding claims 26 to 28, characterized in that a. the first polymer and / or the second polymer are subjected to degassing in the processing step.

30. A process according to claim 26, characterized in that a. the polymer blend or the first polymer and / or the second polymer are subjected to pre-filtration in the processing step. Process according to claim 16, characterized in that a. the polymer blend or the first polymer and / or the second polymer is a fluff or powder before the processing step. Process according to claim 16 to 31, characterized in that a. first polymer and / or second polymers subjected to a processing step can be melted more gently during processing. Process according to claim 16, characterized in that a. the first polymer and / or the second polymer are processed directly in the extruder without a processing step prior to processing. Process according to claim 16, characterized in that a. the first polymer and / or the second polymer are present as production or processing waste. Process according to claim 16, characterized in that a.the first polymer and / or the second polymer is present as a laminate, preferably the laminate comprises two or three films. Method according to one of the preceding claims, characterized in that a. the first polymer and / or the second polymer is present as a laminate, b. preferably, at least two layers of the laminate are bonded together with a polyurethane-based adhesive with a layer thickness of 1-4 gsm.

37. Method according to one of the preceding claims, characterized in that a. the first polymer and / or the second polymer is present as a laminate, b. at least two layers of the laminate are coated with a Acrylic resin dispersion / emulsion adhesive are bonded together, c. the adhesive preferably has a layer thickness of 1-4 gsm.

38. Method according to one of the preceding claims, characterized in that a. the first polymer and / or the second polymer is present as a laminate, b. at least one layer of the laminate is printed.

39. A process according to any one of the preceding claims, characterized in that a. the melt temperature is deliberately increased to enable more efficient decomposition and removal of by-products of the polymer blend in the extruder.

40. A process according to any one of the preceding claims, characterized in that a. the film has two or more layers, and b. the two or more layers are fed either from a single extruder or from several separate extruders.

41. Process according to one of the preceding claims, characterized in that the polymer blend is preferably integrated in a middle layer or in a sub-outer layer of the film produced.

42. A method according to any one of the preceding claims, characterized in that a. barrier layers are integrated into the film produced in order to encapsulate the polymer blend.

43. Method according to one of the preceding claims, characterized in that a. the film is subjected to a plasma post-treatment in order to modify the surface properties of the film. Method according to one of the preceding claims, characterized in that a. in particular the middle layer or the layers containing the polymer blend are specifically foamed by adding chemical and / or physical blowing agents to the polymer blend. Method according to one of the preceding claims, characterized in that a. entraining agents are added to the polymer blend to increase the degassing performance. Method according to one of the preceding claims, characterized in that a. odorous substances are added to the polymer blend to mask or neutralize odors that arise during processing. Method according to one of the preceding claims, characterized in that a. stabilizers are added to the polymer blend to reduce the formation of defects and particles in the material.Method according to one of the preceding claims, characterized in that a. low-viscosity materials or higher-viscosity materials are added to the polymer blend to influence the mixing effect. Method for producing a film by extrusion with at least one layer comprising a polymer blend, characterized in that the polymer blend is processed according to one of claims 1 to 48. A process for producing a film by means of blown film extrusion, flat film extrusion using the cast process, or flat film extrusion using the sheet process, with at least one layer comprising a polymer blend, characterized in that the polymer blend is processed according to one of claims 1 to 48. A process for producing granules for producing a film by extrusion, characterized in that a. the granules comprise a polymer blend comprising at least a first polymer and a second polymer, and that b. at least two of the polymers involved are incompatible with one another. Process according to claim 51, characterized in that a. the polymer blend has at least two glass transition temperatures. Process according to claim 51, characterized in that a. the polymer blend has at least two ranges of characteristic melting temperatures.A film with at least one layer comprising a polymer blend comprising at least a first polymer and a second polymer, characterized in that a. at least two of the polymers involved are incompatible with each other. A film according to claim 54, characterized in that a. the polymer blend has at least two glass transition temperatures. Film according to claim 54, characterized in that b. the polymer blend has at least two melting temperatures. Film according to one of claims 54 and 56, characterized in that a. the film was produced according to one of claims 1 to 53. Plastics forming plant, in particular a blown film plant, a flat film plant for casting processes, or a flat film plant for sheet processes, for producing a film with at least one layer with a polymer blend, comprising at least a first polymer and a second polymer, characterized in that a. at least two of the polymers involved are incompatible with one another. Plastics forming plant according to claim 58, characterized in that a. the polymer blend has at least two glass transition temperatures. Plastics forming plant according to claim 58 or 59, characterized in that a. the polymer blend has at least two melting temperatures.Plastics forming plant according to one of claims 58 to 60, characterized in that a. the plastics forming plant produces the film according to one of claims 1 to 53.

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