Method for producing a film, method for producing particles, film and plastic molding line

Abstract

The invention relates to a method for producing a film having at least one layer comprising 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 each other and the polymer blend is processed in an extruder. The invention also relates to a film having at least one layer comprising 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 each other. The invention also relates to a plastic forming line, in particular a film blowing line or a flat film extrusion line, for producing a film having at least one layer comprising a polymer blend comprising at least a first polymer and a second polymer, characterized in that the polymer blend comprises at least one layer comprising at least one layer comprising at least one layer comprising at least one layer comprising at least one layer comprising at least one layer comprising at least one layer comprising at least one layer comprising at least one layer comprising at least one layer comprising at least one layer, at least two of the polymers involved are incompatible with each other.

Description

[0001] The present invention relates to a method for producing a film having at least one layer comprising a polymer blend, the polymer blend comprising at least a first polymer and a second polymer. The present invention also relates to a film having at least one layer comprising a polymer blend, the polymer blend comprising at least a first polymer and a second polymer, and the present invention further relates to a plastic molding production line for producing a film having at least one layer comprising a polymer blend, the polymer blend comprising at least a first polymer and a second polymer.

[0002] Plastics are polymers composed of long-chain molecules. Different from natural polymers such as cellulose or rubber, the properties and behaviors of synthetic plastics can be precisely controlled. Therefore, synthetic plastics are suitable for a variety of applications in industry and daily life.

[0003] One of the most important properties of plastics is plasticity. By heating the plastic and then cooling it in a mold, the plastic can be formed into almost any desired shape. The plasticity of plastics enables the production of complex geometries and details that are difficult or even impossible to achieve using other materials.

[0004] In addition to plasticity, plastics also have many other properties that make them attractive for various applications. For example, plastics are lightweight, strong, durable, waterproof, chemically resistant, and electrically insulating. These properties make plastics an ideal material for packaging, protective covers, components, and more.

[0005] The remarkable effects achieved by plastics since their inception can be attributed to the widespread use of this material and its various different properties. Plastics are characterized by their very low density, mechanical properties that can be adjusted over a wide range, good processability, very good reprocessability, and numerous other properties.

[0006] Different molecular structures and appropriate preparation and processing methods enable the production of "customized materials" that can be used for various applications.

[0007] However, there are also disadvantages to using plastics. Many plastics are non-biodegradable and can cause environmental pollution if not properly disposed of. In addition, over time, some plastics release toxic substances that are harmful to health. Therefore, it is important to use environmentally friendly and safe methods in the production and disposal of plastic products. The reuse of plastics is also particularly important.

[0008] In recent years, the development of biodegradable plastics has also become increasingly important. These plastics are partially produced from renewable raw materials and can be degraded by microorganisms, for example, without releasing toxic substances.

[0009] Depending on the chemical composition and state of the plastic, plastics can be recycled in different ways. One way is mechanical recycling, in which the plastic is shredded and processed into new products. This method is the simplest for plastics that are still in good condition and can be easily broken down into small pieces. Another way is chemical recycling technology, in which the plastic is broken down into its components and then the components are converted into new plastic products. This method is suitable for plastics that are too contaminated or damaged to be recycled mechanically. Another way is thermal recycling, in which the plastic is burned at high temperatures to generate energy. This method is most suitable for plastics that cannot be recycled anymore.

[0010] Plastics usually consist of a mixture of various polymers because these mixtures can improve certain properties that are important for the intended applications. For example, the tensile strength or durability of plastics can be increased by combining various polymers. Mixtures of various polymers can also help reduce production costs by combining inexpensive polymers with more expensive polymers. Another reason why plastics often exist in the form of mixtures of various polymers is that plastics are easier to process and mold, which is beneficial for the industrial manufacture of large quantities of plastic products.

[0011] However, the presence of the resulting multiple types of plastics sometimes causes problems in the collection and recycling processes. Therefore, plastics have long been considered non-recyclable or only recyclable within very limited ranges. The fact that plastic products are usually composed of various types of plastics, such as multi-layer films and / or film composites, so-called laminates, exacerbates the challenges in terms of recyclability. In this case, the recyclates exist in the form of mixtures of various plastics.

[0012] Select the recycling methods of material, raw material, and energy recovery according to the condition of the recyclates.

[0013] Material recycling is understood as reprocessing plastic waste into new products without significantly changing the molecular structure of the polymer molecules. This method is usually achieved by remelting the plastic. Material recycling is a method by which waste materials composed of various materials are reused to produce new products. This method is often used for plastics, paper, glass, and metals. Different from traditional recycling, in which materials are broken down into their original components and then the original components are converted into new products, material recycling focuses on reusing materials in their existing conditions. This method can help conserve resources and reduce environmental pollution caused by waste.

[0014] In the case of material recycling, there is a difference between direct processing and regranulation. In direct processing, new products are produced directly from waste by a single processing method. On the one hand, this process is currently only used in the case of using mixed plastic waste to produce thick-walled, low-quality molded parts. On the other hand, high-quality waste from a single source is especially directly returned to the manufacturing process through in-house recycling and is thus directly processed into new products.

[0015] However, in most cases, there is an intermediate step of regranulation, that is, plastic waste is melted after being prepared by extrusion to produce high-quality pellets. Then, the high-quality pellets are processed by plastic processors and are processed into corresponding products in the same way as the original materials.

[0016] Plastic regranulation is a method in which used or worn plastics are cut into small pieces and then reprocessed into small pellets. Then, the pellets can be reprocessed into new plastic products, realizing the recycling of plastics. Regranulation is a form of mechanical recycling technology and is often used for plastics such as polyethylene, polypropylene, and polystyrene. Regranulation is an economical, efficient, and environmentally friendly alternative to producing plastic products from crude oil.

[0017] The main advantage of regranulation is the ability to targetedly influence the quality of the regranulation. For example, by targetedly adjusting the extrusion method to suit the properties of the raw materials, the processor obtains regranulation that is easy to handle and can be substantially processed in the same way as the original materials.

[0018] 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 furthermore the molecular structure or the possible crosslinking of the polymers respectively. The problem with blend plastics is that most plastics are incompatible with each other.

[0019] Normally, plastic polymers belonging to the same polymer class can be mixed with each other and can be used in the form of a mixture. Examples of such polymers are polyethylene (PE), polypropylene (PP), and polystyrene (PS). The above materials all constitute polyolefins and are formed by the chain polymerization of olefins. Normally, the polymers can be well mixed with each other and can be processed into various plastic products. However, polymers generated from different chemical structures can also be used in mixtures as long as they are carefully selected and compatible. However, it is important to note that not all polymers are compatible with each other and some mixtures may result in undesirable properties. For this reason, when using plastic mixtures, it is important to carefully plan and test to ensure that the desired properties are achieved.

[0020] The following list describes the miscibility of some commonly used polymers.

[0021]

[0022] The levels range from 1 (miscible) to 6 (immiscible).

[0023] In context, miscibility is understood as the compatibility of various thermoplastics.

[0024] A mixture of two or more different polymers is called a polymer blend or polymer blend body.

[0025] Alternatively or cumulatively, a polymer blend is a mixture of two or more polymers bonded to each other by chemical or physical bonds. Such mixtures are often used to improve certain properties of plastics by combining various polymers with each other. For example, by mixing various polymers with each other, the tensile strength or durability of plastics can be increased. Polymer blends are also often used to reduce the production cost of plastic products by combining inexpensive polymers with more expensive polymers.

[0026] That is to say, in such a polymer blend, the material properties of the polymers are complementary to each other; the properties of the blend depend on whether the polymers involved in the mixture are compatible with each other and the degree of compatibility, that is, whether the polymers involved in the mixture are completely mixed with each other or form separate phases. For this purpose, the required mixing operation is carried out in a screw machine (single-screw extruder, twin-screw extruder, planetary roller extruder, etc.).

[0027] When mixing polymers, the following must be distinguished:

[0028] · A homogeneous mixture of compatible polymers,

[0029] · A polymer mixture that is compatible to a limited extent, and

[0030] · A heterogeneous mixture of incompatible polymers.

[0031] Whether a binary system is miscible can be deduced from thermodynamic considerations. A homogeneous mixture requires a free enthalpy of mixing ΔGm ≤ 0. A polymer blend with a positive Gibbs mixing energy (ΔGm > 0) is a heterogeneous mixture of incompatible polymers.

[0032] Thermodynamic considerations of plastics refer to the application of thermodynamic principles to understand and describe the properties and behaviors of plastics. In relation to plastics, thermodynamic factors can be used to understand how the temperature and state of plastics change under different conditions, and how this affects the properties of plastics. For example, thermodynamic factors help to understand the melting behavior of plastics and predict how the structure and properties of plastics change upon heating and cooling. Thermodynamic factors are also used to study the interactions between plastics and other materials and understand how such interactions affect the properties of plastics.

[0033] Homogeneous mixtures of compatible polymers

[0034] Although the number of compatible polymers is limited, they are of certain significance. The properties of compatible polymers can vary linearly with the proportion of the homopolymer. The following mixtures of compatible polymers are particularly important economically:

[0035] Natural rubber containing polybutadiene and other elastomers

[0036] · Polyphenylene ether (PPE) and polystyrene (PS)

[0037] · Polyamides, such as PA6 and PA10

[0038] · Polyethylene and polyisobutene

[0039] Mixtures of homopolymers with the same monomer groups often exist.

[0040] The basis for generating polymers is understood as monomer groups. A monomer is a molecule that can combine with other monomers to form a linked molecular chain. The linked molecular chain forms the basis of the polymer and determines the chemical properties and behaviors of the polymer. The monomer groups of a polymer can consist of a single monomer called a homopolymer or multiple different monomers called a copolymer. The monomer groups of a polymer have a decisive influence on its properties and behaviors, and the selection of monomer groups is an important factor in the research and development and production processes of plastics.

[0041] A homopolymer is a plastic composed of a single polymer. This means that a homopolymer consists of the same monomers, and there is no difference in the chemical structure and properties of these monomers. Homopolymers are generated, for example, by chain polymerization, in which a large number of monomers combine to form long linked molecular chains. Generally, the properties of homopolymers are very consistent, and since homopolymers are composed of consistent molecules, it is easy to predict the properties of homopolymers. Examples of homopolymers are polyethylene, polypropylene, and polystyrene. Different from homopolymers, a copolymer is a plastic composed of two or more monomers.

[0042] A good example of a mixture of homopolymers with the same monomer groups is a mixture of various polyethylenes, especially a mixture of PE-LD and PE-LLD. Thus, the difficult-to-process PE-LLD is suitable for existing machines, especially during the production of tubular films. Usually, the mixture is generated during the processing of the extrusion method.

[0043] PE-LLD represents polyethylene with low linear density and is a material made of polyethylene. Usually, PE-LLD has a lower linear density. Due to its light weight, durability, and low price, it is often used in the production of plastic packaging, films, and tableware. The low linear density of PE-LLD results in a reduced material density, which leads to a reduced quality and increased flexibility.

[0044] Mixtures of polymers that are compatible to a limited extent

[0045] The most important applications of mixtures of polymers that are compatible to a limited extent can be found in rubber processing, where almost all elastomers are mixed with each other. Rubber processing is a method of processing raw rubber into products such as tires, rubber bands, and other rubber products. The method usually involves multiple 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.

[0046] An elastomer is a material with very good extensibility and elasticity, and it has the property of returning to its original state after being stretched or compressed. Elastomers are often used in industry to produce products such as rubber, natural rubber, and rubber bands. Without the ability to obtain the highest performance by mixing various polymers, it would be impossible to produce tires and other rubber products that meet today's requirements.

[0047] Heterogeneous mixtures (multiphase mixtures) of incompatible polymers

[0048] Mixtures of incompatible polymers are used very widely. Usually, most polymers are immiscible at the molecular level, in other words, they are incompatible. In the case of a mixture of two incompatible polymers, the blend consists of a continuous phase (also called the matrix phase) and a phase dispersed therein (also called the dispersed phase or secondary phase). Different from the homogeneous mixture of (two) compatible polymers in which only one glass transition temperature can be detected, in the case of a heterogeneous mixture of two incompatible (miscible) polymers, two glass transition temperatures can be detected. Plastic waste from multi-component injection molded parts or films such as barrier films (such as PE / PA, PE / EVOH, PE / PA / EVOH, etc.) or laminates (such as PET / PE, PET / PP, PA / PE, etc.) - if they are remelted during the recycling process after use - are typical examples of heterogeneous mixtures of incompatible polymers.

[0049] The glass transition temperature of a plastic is the temperature at which the plastic changes from a solid state to a viscous state. The glass transition temperature of plastics can be different, depending on the type of plastic and its composition. However, generally speaking, the glass transition temperature of plastics is in the range of approximately 100 to 400 degrees Celsius. The glass transition temperature is well below 100 °C, especially in the case of semi-crystalline plastics, i.e., from -150 °C to +400 °C.

[0050] The glass transition temperature or softening temperature (Tg) is the temperature at which glass exhibits the maximum deformation. Glass is a solidified liquid. Glass is formed from, for example, the so-called inorganic glasses such as window glass, but also from organic glasses such as amorphous plastics. The so-called glass transition separates the following brittle energy-elastic region (= glass region) from the upper soft entropy-elastic region (= rubber-elastic region). The transition of amorphous plastics to the flow region is smooth.

[0051] Semi-crystalline plastics have both a glass transition temperature at which the amorphous phase "freezes" (accompanied by embrittlement) below the glass transition temperature, and a melting temperature at which the crystalline phase dissolves.

[0052] When a plastic is heated to its glass transition temperature, it becomes extensible and can be formed into various shapes. After the desired shape is achieved, the plastic is cooled to solidify again. The glass transition temperature is an important factor in the production process of plastic products such as packaging, toys, and electronic parts.

[0053] The structure of a heterogeneous mixture is characterized by the presence of a dispersed phase in a continuous phase. Generally speaking, the mechanical properties of such a heterogeneous mixture 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. By itself - without special intervention - the dispersibility, i.e., fineness, as well as the distribution and adhesion of the dispersed phase are poor. To improve the mixing, i.e., the dispersion and distribution of the dispersed phase, processing machines, especially extruders, should be equipped with suitable mixing elements. In addition to shear flow, those extruders and / or mixing elements also particularly generate tensile flow, which is particularly effective for producing fine particles.

[0054] By dispersion mixing, dispersed phase particles ranging from a few nanometers to several micrometers can be produced, and thus, during good distribution mixing with modern kneading machines (such as planetary roller extruders or twin-screw extruders), the uniform dispersion of the phases in the homogeneous phase is simultaneously achieved.

[0055] Meanwhile, additives can be used to bind the phases to each other by grafting, i.e., to improve adhesion, and such additives are called compatibilizers. A compatibilizer can be a copolymer, half of whose chains are composed of those monomers, each of which is compatible with one of the two phases. In each case, those monomers are incorporated into one of the two phases and thus ensure that the phases are anchored to each other. Both - good mixing and good adhesion - have a positive impact on the mechanical properties.

[0056] That is to say, a compatibilizer is a chemical additive that is used to improve the compatibility of different polymers in a mixture. When different polymers are mixed with each other, compatibilizers are usually used to improve the properties and performance of the material. Compatibilizers can act in various ways, such as by increasing the adhesion between polymers or by influencing the rheological properties of the mixture. In each case, the compatibilizer helps to improve the properties of the mixture and facilitates the processing and use of the material.

[0057] The rheological properties of a mixture refer to its behavior and properties in the liquid state. Rheology is a branch of physics that deals with the deformation and flow of materials, and the rheological properties of a mixture describe how the mixture flows and deforms under specific conditions. Since these properties have an impact on the processing and use of the mixture, such as in the process of casting, extrusion, or injection of the material, these properties are important. The rheological properties of a mixture can be affected by various factors, such as the composition of the mixture, temperature, or pressure.

[0058] However, it should not be overlooked that the change in quality and generally the decrease in quality are, in most cases, related to material recycling. This can be attributed to the fact that the molecular structure changes at least slightly during each processing operation and also changes partially during use. The presence of oxygen during processing leads to oxidation, the influence of temperature leads to thermally induced chain degradation, or the presence of moisture leads to hydrolytic chain scission. During use, chain scission can also be induced in different ways by oxidation, diffusion of substances into the plastic, or by UV irradiation. In addition, even after preparation, used plastics are still at least slightly mixed with other polymers or contaminated.

[0059] It is impossible to make a description of which properties deteriorate and which properties remain unchanged during reprocessing. Therefore, it is important to check what requirements are imposed on the material and what requirements the recycled material meets before using the recycled material to produce products.

[0060] Recycled materials are materials produced from recycled plastics. Different from virgin plastics - also called new plastics - manufactured from crude oil, recycled materials are produced from previously collected used plastics.

[0061] An example of an unwanted change in recycled materials is an increase in the melt flow index (MFI) caused by a decrease in molecular weight in the case of multiple extrusions of PE. Against this background, in the case of material recycling, it is advantageous to directly process the waste without prior preparation steps.

[0062] The melt flow index (MFI) is an indicator of how easily a plastic flows during melting. Usually, the melt flow index is measured through a standardized test process, in which a certain amount of plastic is allowed to flow under certain temperature and pressure conditions. The higher the MFI value, the easier the plastic flows during the measurement process. MFI is commonly used to evaluate the quality and processability of plastics.

[0063] Another problem with co-processing different plastics is that these plastics usually have very different processing temperatures: PE-LD can be melted at temperatures as low as 160 °C and at the same time has a very wide temperature window, while PA6 / 6.6 copolyamides and polyamide 6 or even PET, for example, can only be processed above 245 °C or above 260 °C.

[0064] The different processing temperatures are due to the different temperatures at which different plastics turn into a molten state. Such different temperatures are not uncommon for heterogeneous mixtures and are even typical in the case of plastic waste composed of multiple components as mentioned above. The so-called DSC curve can make these different melting temperatures or more precisely the melting ranges visible.

[0065] The DSC curve is usually a curve generated in the DSC (differential scanning calorimetry) method. DSC is an analytical method used to determine changes in the heat capacity and thermal conductivity of materials. The curve shows the change in the thermal conductivity or heat capacity of the material with temperature. It is often used to study and compare the physico-chemical properties of materials.

[0066] Even the contamination still present in the material can still partially cause problems. The contamination can exist in the form of inorganic particles (such as aluminum or sand) or organic pollutants (such as grease, water, filler materials or paper), which have not been removed through preparation. This can lead to marking, defects, incompatibilities or interactions with polymer molecules, resulting in a decrease in quality.

[0067] Since these problems are addressed during the process of material recycling, many possible methods have been developed that can be used during the pelletizing of waste or can be directly used during reprocessing into new products to improve the material quality:

[0068] · Using stabilizers,

[0069] · Using compatibilizers,

[0070] · Add filling and reinforcing materials,

[0071] · Remove solid dirt particles by melt filtration,

[0072] · Remove volatile components by melt degassing.

[0073] Degassing

[0074] Degassing refers to the method of removing gas from materials. In plastic recycling, degassing is an important step to improve the quality of recycled materials. During the recycling process, air bubbles and other gases can accumulate in plastics, which can have an adverse impact on the quality and processability of the materials. The gases are removed by degassing, which results in a better final product. In the plastic recycling process, there are various possible degassing methods, such as by using vacuum technology or adding degassing agents.

[0075] Like the original materials, degassing provides a way to remove low-molecular components, gases, or air from the melt during processing by extrusion. However, due to the special composition of recycled materials, the substances to be degassed are partially different.

[0076] Degassing tasks that occur more frequently during the plastic recycling process include:

[0077] · Drying: Extract residual moisture, so time-consuming and expensive material pre-drying can be omitted in some cases; it can prevent the formation of air bubbles and a decrease in molecular weight due to hydrolysis.

[0078] · Shift of equilibrium: If low-molecular components are extracted, especially from polycondensates, the equilibrium shifts in the direction of the polymer chain and the molecular weight increases.

[0079] · Removal of external contamination: Most highly volatile organic compounds adhering to plastics in the form of contaminants are removed from the melt. These organic compounds are, for example, fats, oils, and some printing inks or varnishes.

[0080] · Removal of internal contamination: Substances that diffuse into the material during plastic use and cannot be removed by the cleaning process are removed by degassing. These substances are, for example, gasoline, diesel fuel, and antifreeze.

[0081] · Removal of low-molecular degradation products: Degradation products released during processing or use are removed. These degradation products exist in the form of chain fragments, monomers, or oligomers and impair the use and processing properties of plastics.

[0082] · Solvent degassing: Solvents that enter the material due to some of the cleaning and separation stages in the preparation are removed.

[0083] Of course, substances that should have remained in the material will also be partially removed during degassing. These substances can be short-chain polymer components and added additives, especially stabilizers, antioxidants, UV absorbers, plasticizers, etc.

[0084] By specifically increasing the melting temperature, it is possible to significantly increase the decomposition efficiency of by-products such as printing inks. The increase in the melting temperature is related to an increase in the degassing line, which can be used to remove unwanted by-products and / or (foreign) substances. With the increase in temperature, a more intensive decomposition of the printing ink is achieved, thereby releasing harmful substances and gases.

[0085] The melting temperature is preferably adjusted within the corresponding upper limit range of the temperature of the processed material, wherein, preferably, the temperature range is about 90 °C to 350 °C, preferably between 110 °C and 250 °C. It has been proven that it is particularly advantageous to increase the melting temperature within the upper limit range of the temperature of the processed material to ensure the precise decomposition of by-products. At the same time, by precisely controlling the melting temperature, the structural integrity of the actual polymer is ensured, and thus safe processing can be carried out.

[0086] The evolved gases can be captured and provided for special subsequent treatment. For example, this subsequent treatment is used to minimize the environmental impact. This method not only helps to optimize the production process but also pays attention to the environmental protection treatment of the emissions generated during the decomposition process.

[0087] Melt filtration

[0088] During the melt filtration of plastics, the material is transported through a filter element during melting to remove impurities and other solids in the plastics. The plastics are transported through the filter element under pressure and high temperature to filter out the solids in the plastics. Melt filtration is an important step in the plastic recycling process because it helps to improve the quality of the recycled material and remove as many impurities as possible. Melt filtration is often used in combination with other technologies such as degassing to make the recycled material as pure as possible.

[0089] Generally, filtration or straining is understood to mean the separation of solid or liquid particles from a fluid with the assistance of a filter medium. During the extrusion process, filtration thus has the task of separating various foreign particles according to the selected fineness of the filter and thus providing as pure a melt as possible.

[0090] This problem is more serious during the processing of plastic waste. Despite complex cleaning steps during the preparation process, plastic waste still contains more impurities than in the case of virgin plastic materials.

[0091] For reasons of process optimization and profitability, melt filtration must meet the following requirements:

[0092] Filtration at approximately constant pressure and constant temperature

[0093] Filter replacement without interruption and / or impact to production

[0094] Minimum additional residence time of the melt

[0095] Minimal pressure drop in the filter medium

[0096] ·The service life of the filter is as long as possible

[0097] However, due to the very high degree of contamination in some of the plastic waste, conventional filter systems for virgin material quickly reach the limits of these requirements. A foreign body quantity of 0.3% by volume is already considered a very large amount of contaminants for filtration, and even for sieve wheel filters, which are one of the filter systems in continuous operation, an upper contaminant limit of 0.5% by volume is suitable for economic operation.

[0098] Incorporation of additives

[0099] The use of additives during the plastic waste upgrading process can have various advantages. On the one hand, additives can help improve the quality of the recycled material by improving certain properties such as hardness, weatherability or color. On the other hand, additives can help improve the processability of the recycled material by improving melting properties and making the material easier to process. Finally, additives can also help improve the durability of the recycled material by delaying the aging of the material. Overall, additives help improve the properties of the recycled material and increase its value as a raw material.

[0100] The upgrading of plastic waste through additives can be divided into the addition of additives for virgin plastic materials and the addition of additives specifically developed for use in the reprocessing of plastic waste.

[0101] In the first case, the reprocessed plastic can be upgraded by, for example, mineral fillers, reinforcing fibers, color pigments, lubricants, plasticizers, etc. The target selection depends essentially on the desired use of the plastic.

[0102] However, there are some limitations to the upgrading process. For example, in the case of mixed plastic waste, most of it is grey, green or brown. Therefore, it is possible to achieve difficult to define shades by using colour pigments. Although black, dark blue or brown shades can be achieved, lighter shades in particular cannot be achieved.

[0103] A stabilizer is a chemical additive that is used during plastic production to improve the chemical stability of plastics. Stabilizers are often used to protect plastics from damage caused by UV radiation, heat, and other external factors that may adversely affect the chemical structure of the material. Stabilizers can also help delay the aging of plastics and extend their service life. Typically, various types of stabilizers are used depending on the type of damage the plastic may suffer and the properties the plastic should have.

[0104] When stabilizers are used properly, it is important to know the exact history of the recycled material. This includes the stabilizers originally provided and the damage caused during the processing steps already carried out and in use. For this purpose, stabilizers have been specifically developed that prevent the reduction in molecular weight and dark discoloration that occur during reprocessing.

[0105] Polymeric materials are particularly damaged by heat, atmospheric oxygen, light, moisture, high-energy radiation, and by the influence of microorganisms. Therefore, different stabilizers or their combinations must also be used separately for different effects and degradation mechanisms:

[0106] · Antioxidants: Protect the polymer from oxidative degradation by oxygen, especially including the influence of heat during processing.

[0107] · Metals: Protect the polymer from accelerated thermal oxidative degradation. Deactivators: Deactivators are triggered in the case of certain polymers, for example, the presence of metals such as copper or iron triggers deactivation.

[0108] · UV absorbers: Protect the polymer from photoinduced degradation.

[0109] · Biostabilizers: Microorganisms are also able to attack and destroy polymers, especially additives such as plasticizers for PVC.

[0110] The working principle of stabilizers is based on the fact that stabilizers react faster in the presence of, for example, oxygen or light, and thus protect the polymer itself from damage. However, this also means that the stabilizers will gradually be used up, and the polymer will still be damaged after the stabilizers are completely used up. The dosage of stabilizers is usually between 0.05 and 5.0 wt.%, and it was originally only designed for single use of the polymer, so the dosage of stabilizers is crucial. Therefore, subsequent stabilization during reprocessing is necessary.

[0111] In addition to the intended applications and the associated environmental impacts as well as the processing-related conditions, the amount of stabilizer is also determined by the polymer types, which vary greatly in terms of oxidation and photosensitivity. Therefore, optimal subsequent stabilization must take into account previous damage, the existing residual stabilizer content, the reprocessing conditions, and the subsequent applications. However, it must be noted that subsequent stabilization can only maintain the property level of the recycled material to a large extent and cannot increase it beyond that level.

[0112] Compatibilizers are another important additive with regard to plastic reprocessing. The purpose of compatibilization is to improve the properties of heterogeneous mixtures of incompatible polymers. There are two different compatibilization strategies: The first strategy involves adding non-reactive compatibilizers (such as copolymers, nanoparticulates, or ionomers) to the polymer blend to hinder the co-growth (also known as coalescence) of the phases and reduce the degree of dispersion, thereby increasing the adhesion between the phases.

[0113] The compatibilizer is mixed into the starting granulate in amounts on the order of a few percent by weight.

[0114] There are roughly two methods to improve the compatibility of binary or multicomponent heterogeneous mixtures:

[0115] · Adding non-reactive compatibilizers: Adding another, for example, a third component such as a block or graft copolymer or an ionomer, whose components exhibit better compatibility with the two incompatible components of the plastic mixture. Block or graft copolymers are polymers composed of two or more different monomer units linked to each other, where chains of another monomer type are attached to the main chain formed by the monomers in a comb-like manner. Different from linear-linked polymers in which the monomer units are strung together in a single chain, block or graft copolymers have multiple parts including different monomer units. The parts can include different chemical properties and thus affect the properties of the entire polymer. Block or graft copolymers are often used in the production process of plastic mixtures to form binding ligands between polymers that are not easily compatible with each other. Adding nanoparticulates as non-reactive compatibilizers is also known.

[0116] · Reactive compatibilization: Modifying one or two incompatible components by grafting functional groups that have improved compatibility with the other components in each case. Compatibilization, that is, modification, is carried out during the blend formation process. This method is also called reactive compatibilization, and the method is called reactive extrusion. In particular, twin-screw extruders are suitable for tasks associated with reactive extrusion.

[0117] Adding non-reactive compatibilizers

[0118] Adding a copolymer, i.e., a polymer having at least two different monomer units, to a heterogeneous mixture of incompatible polymers can reduce the interfacial tension between the phases, thereby weakening phase separation and promoting the formation of a fine dispersed phase. This operation corresponds to the emulsification of immiscible liquids. Usually, block copolymers (diblock, triblock, and multiblock copolymers) or graft copolymers are used. A prerequisite for using a copolymer as a compatibilizer is that all the polymers in the blend must interact with one of the segments (blocks) in the copolymer. A typical example of a triblock copolymer that has been used as a compatibilizer in various material systems is styrene-ethylene-butene-styrene, which is a thermoplastic elastomer. SEBS has been successfully used in the case of PET / PE and is also used in PET / PP blends to improve the mechanical properties: the use of the compatibilizer results in a more homogeneous morphology, increased elongation at break, and impact strength.

[0119] Using nanoparticles (NP) can also achieve the same improvement in compatibility as that of copolymers. The prerequisite for stabilizing the droplets, i.e., the dispersed phase, is that the NP migrate to the interface between the matrix and the dispersed phase and have an equal attraction to the polymers present in the blend. The NP can have different shapes (spherical or flaky), different chemical structures (silica, calcium carbonate, organically modified montmorillonite), and different sizes, and can include surface coatings (mostly organic molecules).

[0120] Ionomers are thermoplastic copolymers that have "hanging" ionic groups and thus include a relatively low ionic concentration. Due to the presence of secondary valence bond forces (van der Waals forces, dipole-dipole interactions with each other, hydrogen bridge bonds) in the thermoplastics, there are strong electrostatic forces between the polymer chains. Ethylene-methacrylic acid copolymers are shown as examples of ionomers. Among other things, the said compatibilizer is used to make the recycled mixture of PE and PA compatible and to increase the tensile strength, yield strength, elongation at break, impact strength, and hardness compared to the polymer mixture without the compatibilizer. The intermolecular forces reduce the interfacial tension between different phases.

[0121] In addition to ionomers, another thermoplastic, called EVA, is added as a compatibilizer.

[0122] Reactive Compatibility

[0123] Increasing the compatibility by grafting functional groups onto one or more components of a heterogeneous mixture of incompatible polymers is called reactive compatibility. The compatibilizer is usually a copolymer. On the one hand, due to the intermolecular forces between the polar copolymer and the components of the polymer mixture being dominant, and on the other hand, the copolymer forms chemical bonds with another component of the mixture, the homogeneity of the incompatible polymers is improved. The stronger the polarity of the compatibilizer, the greater the intermolecular interaction between the phases.

[0124] The most commonly used compatibilizers in the plastics industry are maleic anhydride (MA)-grafted copolymers. Maleic anhydride (MA)-grafted copolymers react in terms of hydroxyl groups (OH) and amino groups (NH2), and are thus used especially in the case of mixed plastic waste consisting of the polymer chain ends and one of the two groups. The MA-grafted copolymer forms a covalent bond with one of the blend ligands, which improves the mechanical properties.

[0125] Generally, acid anhydrides of unsaturated dicarboxylic acids can be used here to introduce acid anhydride groups as reactive groups. These are preferably produced using the so-called "graft from" graft copolymerization method. The reactive compatibility of PE / PA mixtures is possible, for example, with PE-g-MA, i.e., polyethylene that has been grafted with maleic anhydride. The melting and compounding of the thermoplastic with the compatibilizer results in the formation of van der Waals forces in the PE backbone of the copolymer to form polyethylene, and the acid anhydride groups react with the amino groups of the polyamide. Compared with incompatible blends, the structure of the dispersed phase is more uniform, the size of the pellets is significantly reduced, and the tensile properties are increased.

[0126] Polyethylene grafted with maleic anhydride can also be used as a compatibilizer for PE / PET blends. The acid anhydride groups of the compatibilizer chemically react with the hydroxyl groups at the ends of the PET chains, and the PE part of the PE-g-MA is miscible with the PE component of the polymer mixture due to physical binding forces.

[0127] Other compatibilizers based on maleic anhydride include: for example, SEBS-g-MA for, e.g., PE / PET or PE / PA mixtures, and PP-g-MA for, e.g., PE / PP systems, or EVA-g-MA and EVB-g-MA for, e.g., PE / PET or PE / PA mixtures.

[0128] As an alternative to maleic anhydride-grafted copolymers, copolymers having unsaturated epoxy resins are known, for example, using glycidyl methacrylate (GMA) as a reactive group. In addition, in addition to the above-mentioned GMA and MA, acrylic acid (AA), ethylene-vinyl acetate copolymer (EVA), and maleimide (MI) are commonly used functional groups, which are grafted onto polyolefins or copolymerized into compatibilizers.

[0129] Reactive extrusion can also be used to optimize compatibility through free radical formation: Homogenizing and preparing incompatible plastics in an extruder in combination with a free radical initiator results in the formation of large free radicals. The reactive polymer is capable of forming covalent bonds with other blend ligands and, in this way, enables the formation of graft or crosslinked copolymers. Due to the use of free radical initiators during the mechanical recycling process, the degree of crosslinking of the polymer mixture increases and, in this way, compatibility is increased. However, the presence of free radicals during plastic processing can also lead to oxidative degradation and chain scission, which is why the goal of the reactive extrusion process should be to maximize compatibility and minimize chain breakage.

[0130] The application of compatibilizers lies in the co-processing of plastic waste, the separation of which is technically or economically unfeasible, for example, the reprocessing of co-extruded plastic waste composed of different incompatible polymers. The waste is, for example, multilayer film waste and laminates made of PE and PA, PE and EVOH, or PE and PET or mixtures, such as PE / PET, PE / PA, PP / PET, etc. The co-reprocessing of the plastic fraction from municipal waste (PE, EVA, ionomers, COC, PP, PET, PA, EVOH, and PS, etc.) is also optimized by compatibilizers.

[0131] Co-extruded plastics are plastics composed of multiple layers that are produced synchronously with the aid of an extrusion method. In this method, the individual layers of plastic are transported through a nozzle and extruded synchronously so that the layers adhere to each other. Co-extruded plastics usually have various properties that vary from layer to layer. For example, one layer of the plastic can have certain properties such as hardness or weather resistance, while another layer has other properties such as flexibility or transparency. Co-extruded plastics are often used in the production of packaging, films, and other products that require various properties. Usually, although co-extruded films are produced in one step, in the case of laminates, the individual monolayer films that make up the laminate are produced in separate extrusion processes and these films are joined together in one or more consecutive processes to form a composite material; this is called lamination. Thus, a typical laminate is made of two or three films.

[0132] Waste from production or processing (plastics from post-industrial sources: "PIR" = post-industrial recycling) is waste generated during the plastic production process. The waste can have different forms, for example, in the form of scraps, dust, foam, or incompletely manufactured products. The waste is usually generated by the processing of plastics, for example, by extruding, punching, sawing, or grinding materials. Waste from production or processing constitutes an important source that can be reused or recycled to reduce the environmental impact of the waste and conserve valuable resources.

[0133] Typically, production or processing waste is generated in a substantially uncontaminated manner and is therefore very suitable for material recycling. If the waste comes from a single source, i.e., the waste consists mainly of one basic raw material, such as a PE film, the waste is returned directly from the production line to the material cycle. More precisely, after preparation, the waste is directly processed into new products, for example, by processing methods such as extrusion, injection molding, blow molding, etc., where the prepared material is often mixed with virgin material. In this case, the above method is called internal recycling.

[0134] However, if the production or processing waste includes composite products, that is, for example, injection molded parts made of multiple components or films made of multiple layers and / or film laminates made of different basic raw materials such as PE, EVA, ionomer, COC, PP, PET, PA, and EVOH, and printed films, etc., then preparation starts in a separate preparation step. Therefore, the material properties of the recycled material can be affected in a targeted manner. This can be achieved by adding virgin material, additives, reinforcing or filling materials via reactive extrusion or degassing, and the end result is a recycled material that is very similar in appearance to the pellets of virgin material.

[0135] Post-consumer recycling refers to the recycling of plastics that have been used by the end consumer. Different from the recycling of PIR waste where plastics come directly from production, plastics that are purchased and used by consumers and then discarded are used for post-consumer recycling. The 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 protecting important resources.

[0136] Waste generated after use - i.e., from the post-consumer sector ("PCR" = post-consumer recycling) - has higher requirements for material recycling than production or processing waste, but in principle there is no difference from the latter.

[0137] A laminate made of PET and PE film is an example of waste that is currently available for material recycling only to a very limited extent. These products are available in large quantities in the form of PIR goods and PCR goods. At least one film of the laminate consists mainly of PE raw material with a thickness of 20 to 200 μm, and at least one film consists mainly of PET raw material with a thickness of 8 to 20 μm. Overall, the proportion of PE in the laminate is always greater than that of PET.

[0138] A laminate made of PE is another similar example, where the PE is derived from PET and PP, more precisely from PET and CPP (cast PP) or PET and BO-PP (biaxially oriented PP). At least one film of the laminate consists mainly of PP raw material with a thickness of 10 to 200 μm, and at least one film is mainly made of PET raw material with a thickness of 8 to 20 μm. Generally speaking, usually, the proportion of PP in the laminate is always greater than that of PET.

[0139] The film web can be printed over its entire surface or partially printed using solvent-based or solventless printing inks that are thermally stable or thermally unstable at around 200 °C. Nowadays, the standards for flexographic or gravure printing in the case of flexible packaging are usually based on printing inks containing nitrocellulose, which form toxic gases when recycled in an extruder and cause the formation of corrosion.

[0140] Optionally, the film web can also be coated, especially to increase the barrier effect of the laminate.

[0141] The barrier effect of plastics can be increased by various measures. On the one hand, certain additives such as EVOH (ethylene-vinyl alcohol copolymer) or PVDC (polyvinylidene chloride) can be used to improve the barrier effect of plastics against oxygen, moisture, aroma, and taste. On the other hand, the barrier effect can be increased by applying a coating on the plastic surface. Finally, the thickness of the plastic can also play a role. Generally, thick plastics have a higher barrier effect than thin plastics. Overall, there are various possible methods, among which the barrier effect of plastics can be improved depending on the specific requirements of the material and the application field.

[0142] Plastics are sometimes provided with a metal layer to improve certain properties or add new functions. For example, a metal layer can be used on plastics to increase their electrical conductivity and thus be used as a conductive material. The metal layer can also help improve the resistance of plastics to weathering effects and corrosion by protecting the plastics from damage caused by moisture, UV radiation, or oxygen. Finally, a metal layer can also be used to give plastics a certain color or appearance, such as producing a gold, silver, or metallic color.

[0143] The coating thickness is usually less than 3 μm, usually 2 μm or less, and in some cases only in the range of 3 to 50 nm ("met").

[0144] The film webs are joined together by an adhesive ("adh"). Nowadays, polyurethane-based adhesives with a layer thickness of 1 - 4 gsm are mainly used. Alternatively, an acrylic resin dispersion / emulsion adhesive can also be used.

[0145] Alternatively, an adhesive layer (e.g., EVA) is directly extruded onto a layer in the film web so that the adhesive can be omitted during connection ("coating").

[0146] Examples of laminates that can be used as input materials include:

[0147] 1) PE / / adh / / PET

[0148] 2) PE / / adh / / ink / PET

[0149] 3) PE / / adh / / met-PET / / adh / / ink / PET

[0150] 4) coating / ink / met-PET / / adh / / PE

[0151] 5) PE / / adh / / ink / coating / PET

[0152] 6) PE / / PET

[0153] 7) BO-PP / / adh / / PET

[0154] 8) CPP / / adh / / PET

[0155] 9) met-BO-PP / / adh / / PET

[0156] 10) met-CPP / / adh / / PET

[0157] Multilayer films made of PE / PA, PE / EVOH, PE / PA / EVOH, etc. are another example of waste that is currently only available for material recycling to a very limited extent. Such films are also popularly known as barrier or high-barrier films. These films are configured to minimize contact with certain environmental factors and thus extend the durability of the packaged product. The challenge of material recycling is that the polymers commonly used (e.g., combinations of PE or PP with EVOH and / or PA, etc.) are incompatible with each other, that is, immiscible, i.e., incompatible. Separating the individual components (PE, PP, PA, EVOH, etc.) during the recycling process for targeted recycling is very complex and thus not common. Especially when printing such films (barrier or high-barrier films), these films can only be made available for material recycling to a limited extent - highly diluted. Like the PET / PE laminate, the films are available in large quantities in the form of PIR commodities and PCR commodities.

[0158] Due to the above reasons (e.g., due to printing inks, compatibility caused by different processing temperatures, impurities), the waste cannot currently be directly processed without upstream preparation steps.

[0159] Today, waste from non-single sources can only be offered to material recycling on a small scale. The proportion of waste in new products is small; waste is mixed with virgin material. Typically, the proportion of recyclates in the used layers is less than 30 wt.%, often less than 20 wt.%. Typically, recyclates are prepared, i.e. in direct processing, without producing products again from the waste, but rather the waste is first prepared into pellets.

[0160] The problem with waste from non-single sources is that this waste can include plastics from waste streams from household plastic collections, for example from recycling systems such as yellow bags. Informally, these are referred to as medium or low quality PCR. The material is commercially available in large quantities in the form of pellets, and a known example is plastic recyclate from Green Dot, which is sold under the brand name "Systalen". The composition of the recyclate varies and is not 100% known. In any case, extremely diverse mixtures of plastics are available, even if this consists mainly of PE, i.e. more than 60%, preferably 80%, particularly preferably 90%, and particularly preferably 95% and more PE. It should be expressly pointed out that the composition of the mixture is not limited to plastics, but for example includes a wide variety of impurities; for example, but not limited to impurities introduced by, for example, printing inks.

[0161] In contrast to waste from non-single sources, mention should be made of waste from transport packaging, for example from supermarket delivery areas. This waste can often also be used, since the plastics are rarely contaminated and are also to be understood as recyclate in the context of this application. Often, this waste is in the form of stretch film or dome film and therefore provides a better starting point for high-quality material recycling.

[0162] It is desirable to add 50 wt.% or more of non-single source waste to at least one layer of the film and thus significantly increase the proportion of recycling in the material. In particular, it is desirable to achieve this by direct processing without prior preparation to form pellets. These methods are not possible today.

[0163] The use of twin-screw extruders enables more efficient processing of the starting materials and opens up the possibility of using up to 100% recycled content. Thanks to the twin-screw extruders, different plastics can be better homogenized and integrated into the production process.

[0164] The object of the present invention is to provide such waste from the PIR and / or PCR sections for material recycling. To this end, it is proposed that said waste be used as a mixture for at least one layer of a new film.

[0165] Here, the object of the present invention is to provide an improvement or alternative to the prior art.

[0166] According to a first aspect, the object is achieved by a method for producing a film having at least one layer comprising a polymer blend, the 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 each other and the polymer blend is processed in an extruder.

[0167] If the produced film comprises two or more layers, the two or more layers can be provided from a single extruder or can be provided from a plurality of separate extruders.

[0168] For example, the layer can be a single-layer film. However, it can also be one of the layers in a multi-layer film.

[0169] In an exemplary case of a three-layer film in which the polymer is present in the intermediate layer, the layer distribution can be as follows: 25%-50%-25%. The layer distribution is preferably 20%-60%-20%. The layer distribution is particularly preferably 15%-70%-15%. In particular, the layer distribution is preferably 10%-80%-10%. The preferred aim is to maximize the recyclate in the corresponding recyclate layer. The proportions of the different layers can be precisely adjusted according to the specific requirements of the application. For example, a distribution of 25%-50%-25% enables the recyclate to be evenly integrated into the intermediate layer, while a distribution of 10%-80%-10% enables the maximum amount of recyclate to be concentrated on the inner layer. The flexible layer proportions preferably contribute to obtaining the desired material properties and at the same time ensure the effective utilization of recyclate in film production.

[0170] In an exemplary case of a five-layer film, the layer distribution 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%. In particular, the layer distribution is preferably 7.5%-7.5%-70%-7.5%-7.5%.

[0171] The actual proportions of the layer distribution depend to a large extent on the desired properties of the film to be produced, especially the mechanical properties. By controlling the proportions and / or the choice of materials, especially the proportion of virgin materials in the surface layer and the subsurface layer, the properties can be adjusted in a targeted manner. Certain mechanical characteristics, such as strength, flexibility and durability, can be influenced by changing the parameters.

[0172] For example, a higher concentration of virgin material in the surface layer can enhance strength and abrasion resistance, while a higher concentration of recycled material in the intermediate layer can help minimize the ecological footprint. The precise adjustment of the layer composition enables the production of customized films with the desired performance characteristics for various applications. This flexibility in material selection and layer arrangement helps to tailor the film production to specific requirements and, at the same time, promotes sustainable practices.

[0173] Polymer blends can of course also be present in the surface layer and / or subsurface layer. This provides additional variability in film production as the choice of the layer in which the polymer blend is incorporated has a specific impact on the properties of the final product.

[0174] The location of the polymer blend in each layer enables the integration of different functions in the film to meet the requirements of various applications. This approach highlights the versatility of polymer blends in film production and the ability to adjust the material properties according to the intended use and desired performance.

[0175] As mentioned above, in the production of films, it is possible to choose to manufacture multi-layer composite materials with different numbers of layers. For example, but not limited to, composite materials with 3, 5, 7, and 11 layers can be produced. This flexibility enables the combination of a wide range of material properties and thus the satisfaction of the specific requirements of various applications.

[0176] Another aspect of producing films with recycled materials is the odor that the recycled materials may form. To minimize it, a barrier layer can be added, which is used to seal the odor of the polymer blend, i.e., the odor of the recycled materials. The barrier layer provides an effective solution to reduce the emission of undesirable odors and improve the quality of the produced films.

[0177] Another possibility to minimize the odor is to subsequently treat the film with plasma, where the surface of the film is modified. The treatment can be carried out either offline or online. For example, the online treatment can be carried out after the turning bar, preferably after the film tube or web is unwound, or before the winder. Alternatively, in the case of offline treatment, the film can be unwound again, treated after winding, and then wound again or used for further processing steps. This method shows the various available techniques for minimizing the odor in film production.

[0178] In a further development of the method, the intermediate layer or a layer comprising a polymer blend can be foamed specifically. The method can be achieved by adding chemical and / or physical blowing agents to the polymer blend. The addition of the blowing agents enables controlled foaming, wherein the degree of foam formation can be adjusted according to requirements. The specifically targeted foaming can reduce degassing, thereby resulting in a more efficient and sustainable processing method. In addition, the precise adjustability of the degree of foaming enables the omission of complete degassing, which not only optimizes the processing method but also saves resources. Therefore, the above innovative method contributes to the further development of environmentally friendly processing technologies in the field of recycling.

[0179] The specifically targeted foaming method enables the encapsulation of gas in the material. During the foaming process, preferably closed pores are formed in the material, which enclose the contained gas. The advantage of this is that the gas is effectively sealed, reducing uncontrolled degassing, such as degassing at the nozzle when the material exits the nozzle. The closed pores act as small barriers that enclose the gas within the material and thus minimize the gas released into the surrounding environment. This property not only helps to improve the material properties but also has a positive impact on the environmental balance by reducing the escape of gaseous substances during the processing and utilization of the material.

[0180] The produced films have properties comparable to those of traditional films and can thus be further processed in the usual way. For example, the films are stretchable, which means that the films can subsequently be stretched to improve certain mechanical or optical properties. There are many and diverse applicable possibilities. Therefore, the versatility of the films provides various options for subsequent processing and use in various industrial applications.

[0181] The films can be produced by various manufacturing methods, including, for example, air-cooled blown film extrusion, water-cooled blown film extrusion, cast film or sheet extrusion. This enables flexible adjustment of film production according to specific requirements and application fields.

[0182] Possible raw materials that can be used as recyclates of polymer blends are extremely diverse in their uses and consist of, for example, various types of printed and unprinted polyethylene films or polypropylene films. The materials, including PIR (post-industrial recyclates) and PCR (post-consumer recyclates), have a wide range of applications. Typical application fields of recyclable films cover various fields, including packaging and transportation, hygiene, agriculture, construction, industry, healthcare, the clothing industry, the leisure and outdoor industries, pipes and heating installations, the automotive industry or the electrical industry.

[0183] For example, PE films used for garbage bags, shopping bags, food packaging, shrink and stretch films, covers for books, and liner films in the fields of packaging and transportation can all be recycled. Another example is laminated films used in combination with other materials. The possible applications of the films are diverse and range from industrial packaging to specialized applications in various industrial fields. The raw material types of polymer blends further extend to different types of films in various fields: in the hygiene field, for example, breathable PE films are used, especially in products such as diapers. PE films play a crucial role in agriculture, for example, as greenhouse covers, ground films, silage films, or components of irrigation systems. In the construction industry, PE films are used as, for example, moisture barriers, seals for foundations and sewage pipes, as well as temporary building films and geomembranes, which enables long-lasting prevention of liquid or gas penetration. In industry, films are used in a variety of different ways, such as packages, bags for granules, powders, or liquids, and covers for pallets and barrels. In the healthcare field, films are used for, example, medical packaging, packages, and disposable products, etc. In the clothing industry, films are used, for example, in the production of protective shields. Leisure and outdoor equipment such as tents, backpacks, waterproof bags, and sleeping pads also benefit from films. Films also play a role in pipes and heating devices, especially when used for water pipes. The automotive industry uses films for, example, car covers, seat protection devices, and interior trims. Finally, in the electronics industry, for example, films with antistatic properties protect electronic components, while surface protection films prevent mechanical damage and usually include an adhesive surface.

[0184] The films preferably used as starting materials are also those especially used in food or similar packaging, i.e., the so-called barrier films. These films are often used for further processing, e.g., as lidding films, laminates or as deep-drawing films. In addition to PE, these films usually also include other polymers incompatible with PE, such as polymers including PA, CoPA, PET, EVOH, PVOH, etc. Usually, today's films include 5, 7, 9, 11 or more layers. However, barrier films consisting of only three layers are also known. The structure of the film can be symmetric or asymmetric. Characteristically, the material blocks adjacent to PE (or part of PP) ensure the barrier function, or more precisely the arrangement of the individual materials, or more precisely the arrangement of the layers: for example, PE-HV-PA-HV-PE, PE-HV-EVOH-HV-PE, PE-HV-PA-EVOH-PA-HV-PE are particularly known arrangements. Here, the abbreviation "HV" stands for adhesion promoter. These are symmetrically arranged with the barrier material located in the middle of the film. Asymmetric arrangements with the barrier material at least on the outside of the film composite are also known, but also partly with additional barrier blocks further towards the middle of the film. The typical thickness range of lidding films is 30 to 40 μm, and the thickness of thermoformed films or so-called tubular laminates is 300 μm and even 400 μm or thicker. In the prior art, multi-layer films with barrier materials are currently produced by air-cooled blown film extrusion and water-cooled blown film extrusion and multi-bubble methods (double-bubble and triple-bubble methods), and can also be produced, e.g., as flat films (cast films or sheet films).

[0185] The films that can be used as starting materials (such as PE films or PP films) and barrier films can also be non-stretched or stretched. Examples of stretched films include biaxially stretched PE films (BO PE), biaxially stretched PP films (BO PP), biaxially stretched PA films (BO PA), monoaxially stretched PE films (MDO PE) and monoaxially stretched PP films (MDO PP).

[0186] Laminates are another preferred starting material for polymer blends. Such laminates can come from both PCR film applications and PIR film applications.

[0187] In principle, any of the possible starting materials mentioned can also be produced as films with recycled materials, i.e., one or more layers or even all layers can include polymer blends.

[0188] Recycled materials, namely especially polymer blends, can be used in all known film applications; that is, in principle, any of the films mentioned as possible raw materials above can be produced using recycled materials, that is to say, one or more or all of the layers of the film can comprise a polymer blend.

[0189] Its use can be restricted according to legal requirements and the quality of PIR and / or PCR. However, the following shows particularly preferred applications, which are only examples here and not exhaustive:

[0190] · Garbage bags

[0191] · Shipping bags

[0192] · Construction films

[0193] · Caps

[0194] · Liners

[0195] · Compression shrink

[0196] · Outer packaging

[0197] · Compression packaging

[0198] · Bags and sackings ("heavy duty bags")

[0199] · Shrink hoods

[0200] · Stretch hoods

[0201] · Covering films

[0202] · Silage films

[0203] · Greenhouse coverings

[0204] · Geomembranes

[0205] · Laminated films

[0206] · Symmetric barrier films

[0207] · Asymmetric barrier films

[0208] A polymer blend is generally a material composed of two or more polymers mixed with each other. The various polymers can have different properties, which can improve the overall material. For example, a hard polymer and an elastic polymer can be used to produce a polymer blend to obtain a material with high strength and good extensibility. Polymer blends are often used in the plastics industry to produce materials with specific properties. Polymer blends can also be used to improve the performance of materials and enhance their aging resistance. Polymer blends are also used in other fields, such as medical technology and the construction industry. In addition, polymer blends can be configured according to the definitions described in the prior art.

[0209] Polymers are generally large organic molecular compounds composed of many small molecules, which are the so-called monomers. Polymers exist in many different forms and are widely present in nature and synthetic chemistry. Polymers are the basic components of materials such as plastics, elastomers, and textile fibers. Polymers are mainly divided into two categories: thermoplastics and thermosetting plastics. Thermoplastics are polymers that become soft and extensible at high temperatures but solidify again at room temperature. Thermoplastics are often used in plastic production. Conversely, thermosetting plastics are polymers that remain hard and dimensionally stable at high temperatures. Thermosetting plastics are often used in the production of varnishes and adhesives. In the current case, the polymer is preferably a thermoplastic.

[0210] In the current case, the compatibility of the polymer corresponds to the definition described above for the prior art.

[0211] Description: Shear input, production, or further processing

[0212] The extruder preferably applies a shear input to the polymer blend.

[0213] The shear input is measured in units such as Pascal (Pa) or bar and represents the pressure required to push the material through the nozzle of the extruder.

[0214] The shear input of the extruder depends on various factors, such as nozzle shape, nozzle size, and the viscosity of the material to be extruded. An extruder with a shear input can more easily handle materials with high viscosity and high strength and push these materials through the nozzle.

[0215] The shear input of the extruder plays an important role in the production process of plastic products, especially in the extrusion process of materials such as polymer blends and compounds. A high shear input enables high-quality and high-accuracy processing and shaping of materials. Conversely, a low shear input can lead to impurities, warping, and other quality problems.

[0216] The definitions of the terms will be explained below:

[0217] It is expressly stated that in the context of this patent application, indefinite articles and indefinite numbers, such as "one...", "two...", etc., should generally be understood to represent a minimum value, i.e., "at least one...", "at least two...", etc., unless it can be clearly determined from the context or the specific text of a particular paragraph that the intention is exactly "exactly one...", "exactly two...", etc. In addition, all numbers and all details regarding method parameters and / or device parameters should be understood in a technical sense, i.e., taking into account normal tolerances. Even if restrictive terms such as "at least" are expressly stated, it does not mean that if only "one" is mentioned without using "at least" or the like, it refers to "exactly one".

[0218] The terms listed here are always defined and explained in more detail by reference to the relevant prior art.

[0219] In a further development of the method, the polymer blend has at least two glass transition temperatures.

[0220] The glass transition temperature is generally the temperature at which a material changes from a solid state to a liquid state. The glass transition temperature is a specific temperature at which a material changes from an amorphous state to a crystalline state.

[0221] The glass transition temperature of a material depends on various factors, such as the composition, structure, and viscosity of the material. The glass transition temperature can be determined by measuring the heat capacity of the material with the aid of, for example, differential scanning calorimetry (DSC).

[0222] The glass transition temperature plays an important role in the processing of materials, especially in the production of plastics. Materials with a low glass transition temperature can be processed at lower temperatures. Conversely, materials with a high glass transition temperature require higher temperatures to melt.

[0223] Each polymer generally has only one glass transition temperature. The transition temperatures of the individual polymers are preferably different from each other so that their characteristic glass transition temperatures can be manifested in the polymer blend. Depending on the quality of the individual polymers, the glass transition temperature can also be a temperature range. That is, it is preferably expected that there are at least many glass transition temperatures in the polymer blend because of the different characteristic glass transition temperatures of multiple incompatible polymers.

[0224] In a further development of the method, the polymer blend has at least two characteristic melting temperature ranges.

[0225] The melting temperature is generally the temperature at which a material changes from a solid state to a liquid state. The melting temperature of a material depends on various factors, such as material composition, structure, and viscosity.

[0226] The melting temperature can be determined, for example, by measuring the heat capacity of the material with the aid of differential scanning calorimetry (DSC). The melting temperature can also be determined by directly heating the material in a furnace or by applying laser radiation.

[0227] The melting temperature plays an important role in the processing of materials, especially in the production of plastics. Materials with a low melting temperature can be processed at lower temperatures. Conversely, materials with a high melting temperature require higher temperatures to melt.

[0228] Each polymer typically has a single melting temperature. The melting temperatures of the individual polymers are preferably different from each other so that their characteristic melting temperatures can be manifested in the polymer blend. Depending on the quality of the individual polymers, the melting temperature can also be a temperature range. That is, it is preferably expected that there are at least many melting temperatures in the polymer blend because of the different characteristic melting temperatures of multiple incompatible polymers.

[0229] In a further development of the method, the extruder has mixing elements that apply a shear input to the polymer blend and / or the first polymer and the second polymer to mix and / or homogenize the polymer blend and / or the first polymer and the second polymer.

[0230] The mixing elements are arranged, for example, at the end of the extruder to generate pressure to convey the polymer blend out of the extruder through the nozzle. However, the mixing elements can also be mixing elements arranged at the starting position of the extruder or along a part of the extruder to fully mix the polymer blend or its precursors.

[0231] In the present case, the polymer blend is largely described as two polymers that are incompatible with each other. However, the polymer blend can also be a mixture of more than two polymers, preferably a polymer blend of 2 to 5 polymers.

[0232] In a further development of the method, the extruder is configured as a single-screw extruder that applies a shear input to the polymer blend and / or the first polymer and the second polymer to mix and / or homogenize the polymer mixture and / or the first polymer and the second polymer.

[0233] The single-screw extruder includes a cylinder in which a helical screw is positioned. The helical screw is also called a screw flight or a screw. The screw is driven and advances the material through the nozzle of the extruder.

[0234] The single-screw extruder has many advantages compared to other types of extruders. The single-screw extruder can achieve uniform distribution of the material, high processing speed, and high-quality final products. The single-screw extruder can also be easily adjusted according to the requirements of various materials and applications.

[0235] Single-screw extruders are often used in the plastics industry, especially in the production of plastic profiles, films and sheets.

[0236] In a further development of the method, the extruder is configured as a twin-screw extruder, which exerts a shear input on the polymer blend and / or the first polymer and the second polymer to mix and / or homogenize the polymer blend and / or the first polymer and the second polymer.

[0237] Twin-screw extruders are similar in design to single-screw extruders. However, a twin-screw extruder includes two screws, which are used to push the material through the nozzle of the extruder. The screws can, for example, rotate in opposite directions.

[0238] The extruder is preferably used to melt and homogenize the recycled material into a melt and has a melt flow.

[0239] Twin-screw extruders are multi-axis extruders. In plastics technology, twin-screw extruders are used to prepare and shape plastic melts. In this case, for this purpose, the recycled material or a mixture of materials with the recycled material is transported through a heating cylinder by means of two intermeshing rotating screw shafts and melted.

[0240] For twin-screw extruders, tangential or closely meshing co-rotating twin-screw extruders and tangential or closely meshing counter-rotating twin-screw extruders are usually distinguished based on the center distance between the two screw shafts and the direction of their rotation. Counter-rotating twin-screw extruders introduce less shear force to the material to be extruded and thus exert little pressure on it. Therefore, counter-rotating twin-screw extruders are preferably used during the processing of temperature-sensitive materials. In the present case, co-rotating twin-screw extruders, especially closely meshing co-rotating twin-screw extruders, are particularly preferably used.

[0241] Twin-screw extruders include particularly good mixing effects and can thus prepare the plastics used. In particular, it is particularly advantageous to recycle and / or mix additives using a twin-screw extruder.

[0242] According to one embodiment, the blown film production line has a filter, which has at least one filter element for filtering the melt from the unfiltered side to the filtered side. The filter serves as a dirt collection screen. The filter is preferably a filter from the group comprising: melt filters, extruder screens, filter discs and filter screens. In this case, the filter element can be single-layer or multi-layer or pleated. The filter element can include wire meshes, metal non-wovens and / or sintered fabric laminates.

[0243] The filter is preferably arranged in the melt flow between the extruder and the annular nozzle. The filter can also be part of the extruder. The filter is preferably arranged between the extruder and the melt pump of the annular nozzle.

[0244] According to one embodiment, the twin-screw extruder has at least one degassing unit, which enables the extraction of impurities and contaminants. The degassing unit can be configured as a degassing zone that is part of the extruder. Volatile components can be extracted from the melt using the degassing unit. To improve degassing, it is preferred that the degree of filling in the twin-screw extruder is less than 100%, and particularly preferably, the degree of filling is less than 80%. This degree of filling is preferred because otherwise the melt would be pressed into the degassing connector and overflow from the degassing unit.

[0245] According to one embodiment, the twin-screw extruder has at least one degassing unit that is configured as an atmospheric-pressure degassing unit. In this design, volatile components can be discharged from the degassing unit without applying negative pressure.

[0246] According to one embodiment, the twin-screw extruder has at least one degassing unit that is configured as a negative-pressure degassing unit. In this design, negative pressure is applied to the degassing unit. The negative pressure can be generated by a vacuum pump. This design enables particularly thorough degassing of volatile components. Preferably, the degassing unit, particularly the negative-pressure degassing unit, has means for collecting volatile components, preferably in the form of condensed water.

[0247] In a further development of the method, an entrainer can be used. The use of an entrainer is an effective method for improving the degassing performance during the processing of recycled materials. An entrainer is a special substance that can be introduced into the polymer blend of the recycled materials to release gas during the processing in the extruder. The substance generally affects the degassing performance of the recycled materials by reducing the surface tension and promoting the formation of bubbles. This enables an increase in the diffusion of gas from the recycled materials and enables more effective degassing. A suitable entrainer is selected depending on the specific requirements of the method and the desired material properties. Targeted integration of the entrainer into the production process helps to optimize the quality of the final product while making the processing process more efficient.

[0248] According to one embodiment, the extruder has a recycled material feeder with a stuffing screw. Due to the stuffing screw, the recycled materials can be provided to the extruder particularly uniformly. The recycled material feeder preferably has a hopper in which the stuffing screw is arranged. The stuffing screw is preferably driven by a drive that is independent of the extruder.

[0249] According to one embodiment, a blown film production line has at least two pressure sensors for acquiring the pressure in the melt flow director, in each case preferably in the melt flow director upstream of the extruder and the annular die. The pressure sensors are configured to acquire the melt pressure in the melt flow during operation of the blown film production line.

[0250] According to one embodiment, a blown film production line has at least two pressure sensors for acquiring the melt pressure in the melt flow upstream of the extruder and the annular die in each case. The first pressure sensor is preferably arranged at or outside the extruder. The second pressure sensor is preferably arranged upstream of or at the annular die. In an alternative embodiment, the second pressure sensor is arranged upstream of the annular die melt pump. The extruder and / or the annular die melt pump and / or the recycle material provider can preferably be adjusted in accordance with the melt pressure in the melt flow, which is acquired by the first and / or second pressure sensors upstream of the extruder and / or the annular die.

[0251] According to one embodiment, the blown film production line has two additional pressure sensors for acquiring the melt pressure in the melt flow upstream and downstream of the filter. That is to say, these additional pressure sensors are pressure sensors in addition to the above-mentioned pressure sensors. These additional pressure sensors can be installed upstream and downstream of the filter. However, preferably, the additional pressure sensors are placed upstream of the filter and upstream of the annular die. In the case of this design, the second pressure sensor is preferably located downstream of the filter.

[0252] According to one embodiment, the filter has a cleaning device that continuously and / or discontinuously replaces the filter element. In the present case, the term "replaces" should be understood to mean both cleaning the filter element and introducing a new filter element that has not been previously used as a filter element or has been cleaned before being reused. The introduction can be carried out manually or preferably automatically.

[0253] In a further development of the method, the extruder is configured as a twin-screw extruder having screws running in the same direction, also known as co-rotating. That is to say, in the case of this embodiment, the two screws run in the same direction.

[0254] In a further development of the method, the extruder is configured as a planetary roller extruder that applies a shear input to the polymer blend and / or the first polymer and the second polymer to mix and / or homogenize the polymer blend and / or the first polymer and the second polymer.

[0255] Normally, a planetary roller extruder includes a driven central main shaft, and a plurality of independent planetary main shafts roll along the central main shaft, and the number of the planetary main shafts can be changed. The rotating planetary main shafts are usually additionally guided by an internal toothed bushing (roller cylinder). The movement advances the material through the nozzle of the extruder.

[0256] In a further development of the method, additives are added to the polymer blend and / or the first polymer and the second polymer to improve miscibility.

[0257] An additive is generally a material or an admixture that is added to another material to improve or change the properties of the other material. Additives are often used in the plastics industry to modify materials such as polymers, elastomers, polymer blends and compounds, and to adjust the properties of the materials according to the requirements of the final product.

[0258] Additives can have various functions, such as improving strength, hardness, elasticity, chemical resistance and temperature resistance, aging resistance and color. Additives can also be used to make the material easier to process or to change its optical properties.

[0259] Additives can be added in the form of powder, liquid or paste, and must be carefully selected to achieve the desired properties.

[0260] In order to reduce possible odor nuisances during the polymer processing of the polymer blend, odoriferous substances can be added purposefully. The additives are used to mask or neutralize the odors that may be generated during the recycling process. The purpose of selecting the odoriferous substances is preferably to ensure a comfortable and acceptable environment during the processing without having an adverse effect on the quality of the final product.

[0261] Stabilizers such as antioxidants can be incorporated into the production process of the polymer blend. The stabilizers help to reduce the generation of defects and particles in the material. The addition of antioxidants preferably slows down the degradation of the polymer caused by oxidative stress, which can improve the stability and quality of the polymer blend. This helps to maintain the mechanical and chemical properties of the material and thus optimize the performance of the recycled product.

[0262] In the case of additives, there are many possibilities to influence the mixing effect. For example, during the processing of recycled polymer blends, low-viscosity materials can be used purposefully to influence and / or improve the mixing effect and thus achieve a more homogeneous - i.e., better and thoroughly 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 addition. The MFI provides information related to the fluidity of the molten material and thus affects the processing properties during the manufacturing process.

[0263] For example, the viscosity of a polymer blend can be adjusted by adding virgin materials during the production process. For example, materials with a higher viscosity can be blended to improve the bubble stability during the production process of a blown film production line. The MFI value of the commonly used materials is 1, preferably 0.7, and particularly preferably 0.3 or less. Precise adjustment of the viscosity helps to optimize the processing properties of the polymer blend and improve the quality of the manufactured film, particularly in terms of bubble stability and final product quality.

[0264] In a further development of the method, a compatibilizer is added to the polymer blend and / or the first polymer and the second polymer to improve the miscibility.

[0265] Preferably, the compatibilizer is constructed according to the compatibilizers described in the prior art.

[0266] In a further development of the method, the compatibilizer is a polymer, a block copolymer or a graft copolymer.

[0267] A block polymer is generally a polymer composed of two or more different monomers, which are arranged at regular intervals in the polymer chain in most cases. Block polymers are largely generated by combining two or more polymers with different properties.

[0268] The properties of block polymers mainly depend on the type and arrangement of the monomers and the length of the blocks. Block polymers can include hard and soft regions and can occur in various aggregation states, such as amorphous and crystalline regions.

[0269] Block polymers are often used in the plastics industry to produce materials with specific properties. Block polymers can also be used to improve the performance of materials and increase the aging resistance of materials.

[0270] The production of block polymers requires special methods, such as polymer-polymer coupling or block polymerization reactions. The properties of block polymers can be precisely controlled by selecting the monomers and block lengths to obtain materials with the desired properties.

[0271] Block polymers can be used as additives in polymer blends and compounds to improve the properties of the materials.

[0272] Graft copolymerization is generally a technique used to form polymers where the main chain of the polymer forms the starting point for an extended chain of another monomer type. Thereby, a copolymer is produced, and the chains of the other monomer type are typically attached to the main chain of the copolymer in a comb-like manner. Thus, there is another possibility of developing plastics with new and defined properties. The graft polymer is preferably a material composed of polymers and is produced by a grafting method. In the grafting method, two or more polymers are connected to each other, for example, to produce a raw 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.

[0273] In a further development of the method, the compatibilizer is an EVA polymer or an ionomer polymer.

[0274] The EVA polymer is preferably an ethylene-vinyl acetate copolymer, which is typically produced from ethylene and vinyl acetate. The EVA polymer is preferably a flexible material. EVA preferably improves flexibility, elasticity, and chemical resistance.

[0275] The ionomer polymer is preferably a polymer containing ionic bonds and is thus conductive. The ionomer polymer is typically produced by connecting a polymer and metal ions and, in most cases, is characterized by high strength, chemical resistance, and conductivity.

[0276] In a further development of the method, a compound having a reactive group is grafted onto the first polymer and / or the second polymer to improve miscibility.

[0277] In a further development of the method, the reactive group is an epoxy group, which is preferably introduced by reacting the polymer with glycidyl methacrylate (GMA).

[0278] Generally, in chemistry, an epoxy group refers to a structure in which one carbon atom is bonded to two oxygen atoms. This structure is typically found in epoxides produced by the reaction of phenol and epoxy oil. The epoxy group usually has strong reactivity and can react with various other chemicals such as amines or polyols to produce new compounds with different properties. Glycidyl methacrylate (GMA) is a monomer that is produced, for example, by the reaction of methacrylic acid with epichlorohydrin. GMA belongs to the class of epoxy methacrylates and is an important raw material for the production of epoxy resins and other epoxides. GMA typically has high reactivity and the ability to improve polymer properties, such as by increasing its chemical resistance and / or hardness. GMA is preferably used in various fields of the plastics industry, such as in coating production.

[0279] In a further development of the method, the reactive group is an acid anhydride group, which is preferably introduced by reacting the polymer with maleic anhydride (MA).

[0280] In chemistry, an acid anhydride group typically refers to a special structure in which one carbon atom is bonded to two oxygen atoms. For example, when the water molecules of an acid are removed, an acid anhydride group is formed, and it can be generated by heating or treating with a solvent. Acid anhydrides are usually highly reactive compounds and can react with various chemical substances such as alcohols or amines to form new compounds. Acid anhydrides are often used in the plastics industry as, for example, reaction promoters.

[0281] Maleic anhydride (MA) is an acid anhydride that is generated, for example, by heating maleic acid. Maleic anhydride belongs to the class of dicarboxylic acids and is typically characterized by high reactivity and the ability to improve polymer properties. MA is often used in the plastics industry as, for example, a reaction promoter in the production of polyester resins or a crosslinking agent in the production of polyurethanes. MA can also be used as a plasticizer in PVC plastics.

[0282] In a further development of the method, the polymer blend mainly comprises two types of plastics.

[0283] These two types of plastics preferably make up the largest amount of the material.

[0284] In a further development of the method, the first polymer is a polyolefin or a polymer blend of various different polyolefins.

[0285] Polyolefins are a class of polymers that are typically generated from olefins. In most cases, olefins are organic compounds that include a double bond between two carbon atoms. Examples of olefins are ethylene and propylene. Polyolefins are usually generated by polymerizing olefins and are characterized by high strength, chemical resistance, and weather resistance.

[0286] In a further development of the method, the first polymer is polyethylene or a polymer blend of various different polyethylenes.

[0287] Polyethylene (PE) is a polymer that is typically generated from ethylene. Polyethylene belongs to the class of polyolefins and is one of the most produced polymers in the world. PE is largely characterized by high strength, chemical resistance, and weather resistance. PE is used in the production of, for example, films, foams, pipes, and cable insulation.

[0288] In a further development of the method, the first polymer is polypropylene or a polymer blend of various different polypropylenes.

[0289] Polypropylene (PP) is a thermoplastic that is typically generated by the chain polymerization of propylene. Polypropylene belongs to the class of polyolefins and is semi-crystalline and non-polar. The properties of polypropylene are similar to those of polyethylene; however, generally, polypropylene is harder and more heat-resistant.

[0290] In a further development of the method, the second and possibly existing third polymer is a barrier polymer. The barrier polymer is preferably from the group comprising: EVOH, PA, PET, PE, PP, and PVC. Strictly speaking, PET, PE, and PP are not traditional barrier polymers.

[0291] A barrier polymer is a polymer that generally provides a barrier to the movement of molecules or ions through it. Barrier polymers are used in many applications, such as food packaging. Barrier polymers are generally made from materials such as polyethylene, polypropylene, or polyethylene terephthalate (PET), which are known to have durability as well as chemical and moisture resistance. The specific properties of a barrier polymer depend on its chemical structure and the type of molecules it is to block.

[0292] EVOH, PA, PET, PE, PP, and PVC are all various types of plastics in each case. A quick overview of each type is given separately below:

[0293] EVOH or ethylene-vinyl alcohol is a copolymer that is commonly used as a barrier material in packaging applications. EVOH or ethylene-vinyl alcohol is known to have high barrier properties to oxygen and moisture, which makes it useful for the preservation of food and other perishable products.

[0294] PA or polyamide is a polymer that is also known as nylon. PA or polyamide is generally a strong and durable material that is used in a variety of applications.

[0295] PET (polyethylene terephthalate) is a polymer that is often used in the production of plastic bottles, packaging materials, and other products. PET is generally known to have strength and barrier properties, making it a good choice for packaging applications.

[0296] PE or polyethylene is a plastic used in various applications, typically including use in food packaging, bottles, and medical devices. PE or polyethylene is generally known to have flexibility, chemical resistance, and durability.

[0297] PP or polypropylene is a plastic that is often used in various applications, such as in food containers, packaging materials, and automotive parts. PP or polypropylene is generally known to have durability, light weight, as well as chemical and heat resistance.

[0298] PVC (polyvinyl chloride) is a plastic that is often used in various applications, such as in pipes, cables, and flooring. PVC is generally known to have durability, flexibility, and chemical resistance.

[0299] In a further development of the method, the second polymer is EVOH or a polymer blend of different EVOHs.

[0300] In a further development of the method, the second polymer is PA, preferably a PA6 / 6.6 copolyamide or polyamide 6, or a polymer blend of multiple PAs.

[0301] In a further development of the method, the proportion of PA in the polymer blend is less than 50 wt.%, preferably less than 35 wt.%, and particularly preferably less than 25 wt.%.

[0302] It is also possible to add virgin materials to the polymer blend. For example, polyolefins, preferably polyethylene, can be added as virgin materials. The amount of virgin materials can vary depending on the quality of the raw materials of the polymer blend or the proportion of foreign substances in the polymer blend.

[0303] Normally, the virgin materials mainly consist of polyethylene.

[0304] In a further development of the method, the second polymer is PET or a polymer blend of multiple different PETs.

[0305] In a further development of the method, the proportion of PET in the polymer blend is less than 2.5 to 50 wt.%, preferably 3.5 to 37.5 wt.%, and particularly preferably 4.5 to 25 wt.%.

[0306] In a further development of the method, the first polymer and / or the second polymer undergoes a preparation step before being processed in an extruder.

[0307] In plastics engineering, normally, the preparation step refers to various methods for producing polymers. The steps include, for example, the pretreatment and preparation of raw materials, polymerization reactions (the bonding of smaller molecules to form larger polymers), the shaping of polymers, and the subsequent post-treatment of the shaped plastics. Normally, the purpose of the preparation step is to improve the properties and quality of the polymers and make these polymers suitable for their intended applications.

[0308] In a further development of the method, the first polymer and / or the second polymer exists in the form of pellets before being processed in an extruder.

[0309] In this example, the first polymer and / or the second polymer can be specifically subjected to a preparation step so that they already exist in the form of a blend in pellet form. This upstream processing enables different polymer components to be combined into a homogeneous mixture that exists in pellet form. This means that the polymers do not exist separately but preferably already in the form of a proportionate blend mixture. The preformed pellets offer many advantages in further processing due to the improved handling and dosing during the production process. Thus, the targeted preparation in pellet form not only facilitates the processing steps but also contributes to increased efficiency and consistency in manufacturing recycled polymers.

[0310] The advantage that the first polymer and / or the second polymer are already in pellet form also lies in better degassing. Another advantage is, for example, a gentler melting. Since pellets of the first polymer and / or the second polymer are used in the production method, this enables a gentler melting in this method. This results in improved temperature control and enables the melting temperature to be precisely adjusted. The term "gentle melting" refers to the process of heating to the molten phase at a controlled and gradually increasing temperature. This occurs without a sudden or rapid increase in temperature to minimize potential thermal stress. The aim is to maintain the structure and properties of the material as much as possible during melting and at the same time ensure the desired processing properties. Thus, the use of polymer pellets helps to minimize potential thermal stress and achieve effective homogenization of the melt. This not only promotes the optimal handling of the material but also contributes to maintaining the structural integrity of the produced film, which is particularly important in terms of quality standards and material lifespan.

[0311] The upstream preparation of the polymer blend can be carried out, for example, in a single-screw extruder or a twin-screw extruder. The extruder is used to melt, mix, and homogenize the polymer blend. A single-screw extruder includes a single rotating screw, while a twin-screw extruder includes two parallel rotating screws. Both types of extruders are capable of effectively processing the polymer blend and shaping the polymer blend into the desired form.

[0312] Furthermore, the preparation can be carried out with or without degassing. That is, during the degassing process, gases that are generated or more precisely escape and are converted into the gas phase during melting - such as low-molecular impurities - are removed from the material. This is crucial for improving the quality of the final product and minimizing possible defects. The decision regarding degassing during the preparation process depends on the specific requirements of the recycling process and the desired material properties.

[0313] At least one of the polymer blend or its polymers can be pre-filtered during the preparation step. This can be advantageous for reducing mechanical consumption. The pre-filtering enables a simpler construction of the machine, the use of cheaper filters, and / or a reduction in the frequency of necessary filter replacements. In this case, for example, a screen changer with backwashing can be dispensed with. The pre-filtering preferably helps to reduce the specks generated in the final product, since larger impurities have been removed before upstream processing.

[0314] Another advantage of the pre-pellets is that, in some cases, it is possible to avoid using a second melt pump that may be present. This not only optimizes the efficiency of the recycling process, but also saves costs and simplifies the overall configuration of the system.

[0315] Another advantage of the preparation step is that the polymer blend can already be degassed during the preparation. This not only helps to improve the overall degassing performance, but also reduces the odor nuisance during the actual processing. That is, the two-stage degassing during the preparation and the actual processing can increase the proportion of recycled materials. Therefore, the use of degassed pellets during the preparation stage serves as a pre-degassing.

[0316] The preparation step can also process fluff into pellets. The preparation step helps to mix a very large number of material streams and can more easily compensate for batch fluctuations. Smaller material streams can be mixed, thus increasing the versatility of recycled material processing. The pellets obtained from the preparation step melt more uniformly and more rapidly than the fluff added to a method that does not include the preparation step.

[0317] During the processing in a twin-screw extruder, using the pellets from the preparation step has many advantages. This enables a gentler treatment of the polymer mixture, extends the degassing zone of the screw, and helps to reduce possible temperature peaks. Conversely, this preferably results in a reduction in specks, a decrease in the proportion of unmelted material in the polymer mixture, and an improvement in the melting performance. The pellets from the preparation step preferably help to achieve a more uniform processing, which can be reflected in a stable extrusion pressure and a uniform temperature throughout the processing.

[0318] In a further development of the method, the first polymer and / or the second polymer are directly processed without a preparation step before processing in an extruder.

[0319] That is to say, the polymer can directly come from production or processing waste and / or waste that has been utilized by the end consumer.

[0320] That is to say, in the context, the polymer does not necessarily have to be in the form of pellets. For example, the polymer can be in the form of shredded packaging parts from the above two sources.

[0321] The main materials for producing polymer blends using shredded packaging components can be highly diverse and exist in different forms. This can be done, for example, in the form of shreds or flakes or fluff or even powder produced in raw material form.

[0322] The main materials can be in various states, including web materials, mixtures of web materials and / or pellets. The materials can include virgin materials and plastics that have been recycled (PC - Post - consumer recyclates, PIR - Post - industrial recyclates).

[0323] In addition, the main materials can exist in a ready - to - use form. For example, the main material can also be, for example, shredded goods, pellet mixtures, powders, filler materials, or even empty used packaging or unused packaging. Such possible main materials provide a flexible basis for the production of polymer blends and enable the targeted influencing of the properties of the final product. Due to the integration of different main materials, plastic waste can be processed in a sustainable and resource - saving manner.

[0324] In a further development of the method, the first polymer and / or the second polymer are used as waste from production or processing.

[0325] Additives from the group including processing materials, virgin materials, and other materials can be added to the production or processing waste. The other materials can be any other polymer.

[0326] In a further development of the method, the first polymer and / or the second polymer exist in the form of a laminate. The laminate preferably includes two to five layers. However, the laminate can also be a laminate with more than five layers, for example, an eleven - layer laminate.

[0327] The laminate can be in the form of films glued together or as separate films, i.e., for example, a PET film before being bonded to a PE film. In other words, the laminate can be a precursor of the laminate. For example, the precursor of the laminate is still separate layers that have not yet been bonded to each other.

[0328] In a further development of the method, the first polymer and / or the second polymer exist in the form of a laminate, and at least two layers in the laminate are preferably connected together with a polyurethane - based adhesive having a layer thickness of 1 - 4 gsm.

[0329] Generally speaking, polyurethane-based adhesives are adhesives produced based on polyurethane. Polyurethane is a synthetic polymer, usually made from isocyanates and polyols. Generally speaking, the above-mentioned adhesives have high bonding strength and are therefore usually suitable for bonding different materials. Generally speaking, the above-mentioned adhesives are elastic and can thus be used for materials with different coefficients of expansion without damaging the adhesion of the adhesive. Standard polyurethane-based adhesives come in various forms, such as spray adhesives, liquid adhesives, or adhesive pads.

[0330] There are various methods to measure the layer thickness of a film, and the layer thickness ranges from 1 to 4 gsm (grams per square meter). One of the methods is to use a film thickness gauge developed for measuring films. Most of these devices use electromagnetic waves to determine the thickness of the film. Another method is to directly measure the thickness of the film using a micrometer. Place the film between the two contact surfaces of the micrometer and measure the thickness based on the movement of the contact surfaces. Importantly, the film should be smooth and flat so that the measurement is accurate.

[0331] In a further development of the method, the first polymer and / or the second polymer exist in the form of a laminate. At least two layers of the laminate are preferably joined together with an acrylic resin dispersion / emulsion adhesive. The adhesive preferably has a layer thickness of 1 to 4 gsm.

[0332] Acrylic resin dispersion or acrylic resin emulsion adhesives are generally adhesives produced based on acrylic resins. Generally speaking, acrylic resins are dissolved in water or other solvents in the form of small particles to obtain a uniform dispersion or emulsion. Most of the above-mentioned adhesives have strong adhesion and good aging resistance.

[0333] In a further development of the method, the first polymer and / or the second polymer exist in the form of a laminate. Preferably, at least one layer in the laminate is printed.

[0334] The film web can be printed in whole or in part. The printing ink can be solvent-based or solvent-free. The printing ink preferably has thermal stability or instability at 200 °C.

[0335] According to a second aspect, this object is achieved by a method for producing a film by means of extrusion, the film having at least one layer with a polymer blend, which polymer blend is processed in the above-mentioned manner.

[0336] According to a third aspect, this object is achieved by a method for producing a film by means of blown film extrusion, flat film extrusion using a casting method, or flat film extrusion using a sheet film method, the film having at least one layer with a polymer blend, the method being characterized in that the polymer blend is processed according to any one of claims 1 to 33.

[0337] According to a fourth aspect, this object is achieved by a method for producing pellets for use in the production of a film by extrusion, the method being characterized in that the pellets have a polymer blend comprising at least a first polymer and a second polymer, and at least two of the polymers involved are incompatible with each other.

[0338] In a further development of the method, the polymer blend has at least two glass transition temperatures.

[0339] The glass transition temperature has already been defined and described above.

[0340] In a further development of the method, the polymer blend has at least two characteristic melting temperature ranges.

[0341] The melting temperature has already been defined and described above.

[0342] According to a fifth aspect, this 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 each other.

[0343] The compatibility of the polymers has already been defined and described above.

[0344] In a further development of the film, the polymer blend has at least two glass transition temperatures.

[0345] The glass transition temperature has already been defined and described above.

[0346] In a further development of the film, the polymer blend has at least two melting temperatures.

[0347] The melting temperature has already been defined and described above.

[0348] In a further development of the film, the film is produced according to the described method.

[0349] According to a sixth aspect, this object is achieved by a plastics forming production line for producing a film, in particular a blown film production line, a flat film extrusion production line for a casting method or a flat film extrusion production line for a sheet film method, the 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 each other.

[0350] In a further development of the plastics forming production line, the polymer blend has at least two glass transition temperatures.

[0351] The glass transition temperature has already been defined and described above.

[0352] In a further development of a plastic molding production line, the polymer blend has at least two melting temperatures.

[0353] The melting temperature has already been defined and described above.

[0354] In a further development of a plastic molding production line, a film is produced according to any of the types described.

[0355] The embodiments shown herein are only representative examples of the present invention and should not therefore be construed as limiting. Alternative embodiments that occur to those skilled in the art also fall within the scope of protection of the present invention.

Claims

1. A method for producing a film, the film having at least one layer comprising a polymer blend, the 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, and b. The polymer blend is processed in an extruder.

2. The method according to claim 1, Characterized in that: a. The polymer blend has at least two glass transition temperatures.

3. The method according to any one of claims 1 or 2, Characterized in that: a. The polymer blend has at least two characteristic melting temperature ranges.

4. The method according to any one of the preceding claims, Characterized in that: a. The extruder has a mixing element that applies a shear input to the polymer blend and / or the first polymer and the second polymer to mix and / or homogenize the polymer blend and / or the first polymer and the second polymer.

5. The method according to any one of the preceding claims, Characterized in that: a. The extruder is configured as a single-screw extruder that applies a shear input to the polymer blend and / or the first polymer and the second polymer 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 configured as a twin-screw extruder that applies a shear input to the polymer blend and / or the first polymer and the second polymer to mix and / or homogenize the polymer blend and / or the first polymer and the second polymer.

7. The method according to claim 6, Characterized in that: a. The extruder is configured as a twin-screw extruder having co-rotating screws.

8. The method according to any one of the preceding claims, Characterized in that: a. The extruder is configured as a planetary roller extruder that applies a shear input to the polymer blend and / or the first polymer and the second polymer to mix and / or homogenize the polymer blend and / or the first polymer and the second polymer.

9. The method according to any 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. The method according to any one of the preceding claims, Characterized in that: a. A compatibilizer is added to the polymer blend and / or the first polymer and the second polymer to improve miscibility.

11. The method according to claim 10, Characterized in that: The compatibilizer is a polymer, a block polymer or a graft polymer.

12. The method according to claims 10 and 11, Characterized in that: The compatibilizer is an EVA polymer or an ionomer polymer.

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

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

15. The method according to any one of claims 13 and 14, characterized in that: The reactive group is an acid anhydride group, and the acid anhydride group is preferably introduced by the reaction of the polymer with maleic anhydride (MA).

16. The method according to any one of the preceding claims, characterized in that: a. The polymer blend mainly comprises two types of plastics.

17. The method according to any one of the preceding claims, characterized in that: a. The first polymer is a polyolefin or a polymer blend of different polyolefins.

18. The method according to any one of the preceding claims, characterized in that: a. The first polymer is polyethylene or a polymer blend of different polyethylenes.

19. The method according to any one of the preceding claims, characterized in that: a. The first polymer is polypropylene or a polymer blend of different polypropylenes.

20. The method according to any one of the preceding claims, characterized in that: a. The second polymer and the possible third polymer are barrier polymers, and the barrier polymers preferably come from the group including the following: EVOH, PA, PET, PE, PP, and PVC.

21. The method according to any one of the preceding claims, characterized in that: a. The second polymer is EVOH or a polymer blend of different EVOHs.

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

23. The method according to any one of the preceding claims, characterized in that: a. The proportion of PA in the polymer blend is less than 50 wt.%, the proportion of PA in the polymer blend is preferably less than 35 wt.%, and the proportion of PA in the polymer blend is particularly preferably less than 25 wt.%.

24. The method according to any one of the preceding claims, characterized in that: a. The second polymer is PET or a polymer blend of different PETs.

25. The method according to any one of the preceding claims, characterized in that: a. The proportion of PET in the polymer blend is 2.5 to 50 wt.%, the proportion of PET in the polymer blend is preferably 3.5 to 37.5 wt.%, and the proportion of PET in the polymer blend is particularly preferably 4.5 to 25 wt.%.

26. The method according to any one of the preceding claims, characterized in that: a. The first polymer and / or the second polymer are treated in a preparation step before being processed in the extruder.

27. The method according to claim 26, wherein: a. The first polymer and / or the second polymer are in the form of pellets before being processed in the extruder.

28. The method according to claim 27, wherein: a. The first polymer and the second polymer are in the form of a blend before being processed in the extruder, and preferably, the first polymer and the second polymer are in the form of a well - mixed blend mixture.

29. The method according to any one of the preceding claims 26 to 28, wherein: a. The first polymer and / or the second polymer are degassed in the preparation step.

30. The method according to any one of the preceding claims 26 to 29, wherein: a. The polymer blend or the first polymer and / or the second polymer are pre - filtered in the preparation step.

31. The method according to any one of the preceding claims 26 to 30, wherein: a. The polymer blend or the first polymer and / or the second polymer are in the form of fluff or powder before the preparation step.

32. The method according to any one of the preceding claims 26 to 31, wherein: a. The first polymer and / or the second polymer treated in the preparation step can be melted more gently during processing.

33. The method according to any one of the preceding claims, wherein: a. The first polymer and / or the second polymer are directly processed in the extruder without including the preparation step before processing.

34. The method according to any one of the preceding claims, wherein: a. The first polymer and / or the second polymer are in the form of production or processing waste.

35. The method according to any one of the preceding claims, wherein: a. The first polymer and / or the second polymer are in the form of a laminate, and preferably, the laminate includes two or three layers of film.

36. The method according to any one of the preceding claims, wherein: a. The first polymer and / or the second polymer are in the form of a laminate, b. Preferably, at least two layers in the laminate are bonded together by a polyurethane - based adhesive, and the polyurethane - based adhesive has a layer thickness of 1 - 4 gsm.

37. The method according to any one of the preceding claims, wherein: a. The first polymer and / or the second polymer are in the form of a laminate, b. At least two layers in the laminate are bonded together by an acrylic resin dispersion / emulsion adhesive, and c. The adhesive preferably has a layer thickness of 1 - 4 gsm.

38. The method according to any one of the preceding claims, wherein: a. The first polymer and / or the second polymer are in the form of a laminate, b. At least one layer in the laminate is printed.

39. The method according to any one of the preceding claims, characterized in that: a. the melting temperature is increased in a targeted manner so as to be able to more effectively decompose and remove by-products of the polymer blend in the extruder.

40. The method 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 from a single extruder or from a plurality of separate extruders.

41. The method according to any one of the preceding claims, characterized in that: the polymer blend is preferably integrated into an intermediate layer or a subsurface layer of the produced film.

42. The method according to any one of the preceding claims, characterized in that: a. a barrier layer is integrated into the produced film to seal the polymer blend.

43. The method according to any one of the preceding claims, characterized in that: a. the film is subjected to a subsequent plasma treatment to change the surface properties of the film.

44. The method according to any one of the preceding claims, characterized in that: a. in particular, the intermediate layer or the layer containing the polymer blend is foamed in a targeted manner by adding chemical and / or physical blowing agents to the polymer blend.

45. The method according to any one of the preceding claims, characterized in that: a. an entrainer for improving the degassing performance is added to the polymer blend.

46. The method according to any one of the preceding claims, characterized in that: a. an odorant for masking or neutralizing odors generated during processing is added to the polymer blend.

47. The method according to any one of the preceding claims, characterized in that: a. a stabilizer is added to the polymer blend to reduce the formation of defects and particles in the material.

48. The method according to any one of the preceding claims, characterized in that: a. a low-viscosity material or a high-viscosity material is added to the polymer blend to affect the mixing effect.

49. A method for producing a film by extrusion, the film having at least one layer comprising a polymer blend, characterized in that: the polymer blend is processed according to any one of claims 1 to 48.

50. A method for producing a film by blown film extrusion, flat film extrusion using a casting method or flat film extrusion using a sheet method, the film having at least one layer comprising a polymer blend, characterized in that: the polymer blend is processed according to any one of claims 1 to 48.

51. A method for producing pellets for producing a film by extrusion, characterized in that: a. the pellets comprise a polymer blend, the polymer blend comprising at least a first polymer and a second polymer, and b. at least two of the polymers involved are incompatible with each other.

52. The method according to claim 51, characterized in that: a. the polymer blend has at least two glass transition temperatures.

53. The method according to claim 51, characterized in that: a. The polymer blend has at least two characteristic melting temperature ranges.

54. A film having at least one layer comprising a polymer blend, the 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.

55. The film according to claim 54, characterized in that: a. The polymer blend has at least two glass transition temperatures.

56. The film according to claim 54, characterized in that: b. The polymer blend has at least two melting temperatures.

57. The film according to any one of claims 54 and 56, characterized in that: a. The film is produced according to any one of claims 1 to 53.

58. A plastic molding production line for producing a film, the plastic molding production line being in particular a blown film extrusion production line, a flat film extrusion production line using a casting method or a flat film extrusion production line using a sheet method, the film having at least one layer comprising a polymer blend, the 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.

59. The plastic molding production line according to claim 58, characterized in that: a. The polymer blend has at least two glass transition temperatures.

60. The plastic molding production line according to claim 58 or 59, characterized in that: a. The polymer blend has at least two melting temperatures.

61. The plastic molding production line according to any one of claims 58 to 60, characterized in that: a. The plastic molding production line produces the film according to any one of claims 1 to 53.

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