CONTAINER WITH A COATING LAYER

Abstract

The invention is in the field of food and beverage containers. A method is provided for applying a coating layer onto a container preform using plasma deposition. A container preform is also provided, as well as a container that can be obtained by stretching the preform.

Description

CONTAINER WITH A COATING LAYER Background of the invention The invention relates to the field of food and beverage containers, as well as to methods for preparing these containers and the preforms used in these methods. In particular, the present invention relates to these methods and to containers and / or preforms for such containers with a coating layer applied thereto. In the food and beverage industry, a wide variety of containers are used to keep the contents of the containers fresh. Such beverage containers can be made from different materials. Due to their light weight and strength, polymer materials, such as plastics, particularly thermoplastics, are often used for food and beverage packaging. Suitable polymer materials for food and beverage containers include polyesters, such as polyethylene terephthalate (PET), polylactic acid (PLA), polyethylene 2,5-furandicarboxylate (PEF), and other widely available materials such as polypropylene (PP) and polyethylene (PE). Containers made of thermoplastic polymers can be produced by blow molding. In this process, a container preform is produced, for example, by injection molding. A container is then produced by reheating the preform using infrared radiation and stretching it to its final shape, typically in a single blow molding stage (also known as stretch blow molding). Transporting empty containers is inefficient. Therefore, container preforms are often produced in one location and transported to another, where they are blow-molded to their final dimensions and filled. In view of waste reduction and environmental impact, it is desirable that containers be recyclable. Polymers such as PET, PP, and PE are widely recycled, and there is a good infrastructure for recycling such materials, making their responsible disposal convenient. To maintain high-quality recycled material, it is desirable to use pure materials, that is, plastics that do not contain many other materials. A special type of beverage container is the pouch-in-a-container. This type of container comprises an inner layer, i.e., an inner container or pouch, in which a fluid is contained, and an outer layer, i.e., an outer container, which provides structural integrity to the pouch-in-a-container. To empty the inner container, high gas pressure (relative to atmospheric pressure) can be applied between the outer and inner containers. This causes the fluid to be distributed from the pouch without allowing gas to enter the pouch, thus keeping the contents cool. LAnann / zznz / E / YiAi container. Bags-in-containers are used, for example, in draft beer systems. Bags-in-containers can be produced by creating a preform comprising an inner layer (i.e., an inner preform) and an outer layer (i.e., an outer preform), and integrally blow-molding this double preform into a bag-in-container. During blow molding, the inner layer of the preform is stretched to become the inner layer of the container, and the outer layer of the preform is stretched to become the outer layer of the container. In view of recyclability, it is desirable that the inner and outer container of a bag-in-a-container be made of the same material. For the proper functioning of bag-in-can systems, it is important that the inner container, or bag, delaminates from the outer container during use. This can be achieved by using different materials for the inner and outer containers, which do not adhere well to each other. However, using different materials for the preform or the inner and outer containers has disadvantages for container recycling. Integral blow molding of preforms made of different materials into a bag-in-can can also be difficult, particularly because different materials typically exhibit different reheating behavior in the infrared. In this process, release agents are applied to the inner preform to optimize delamination. Typically, release agents such as silicone and PTFE are applied, for example, by spraying, to the outer surface of the inner preform. One disadvantage of using such release agents is their tendency to flow across the surface, resulting in uneven distribution of the release agent. This can also lead to some areas of the surface not being coated at all. Furthermore, the application of release agents can contaminate the surrounding environment, such as the machinery used, and can interfere with subsequent processing steps, such as welding. Another process for optimizing delamination is to increase the roughness of one of the preforms by incorporating metal flakes, as described in WO2014077681. This process can be used as an alternative to release agents. However, depending on the situation, it may still be advantageous to additionally apply a release agent to the outside of the inner preform before blow molding to further promote easier and more controlled release of the inner and outer containers. Document EP2148770 describes a pouch-in-a-container made of an inner and an outer preform of the same material, wherein the inner and outer layers of the container are released. The application of a release agent is advantageous in some cases. One objective of the present invention is to provide containers having at least one treated surface, wherein the treatment is used to add various functionalities to the container. Another The objective of the present invention is to provide coated containers or container preforms, the coating of which can be used to add various functionalities to the container, without adding a large amount of extra material to the container, thus maintaining good recyclability of the container. Brief description of the invention According to the invention, a method is provided for applying a coating layer onto a preform for a container using plasma deposition. In addition, a method for producing a container is provided. According to another aspect of the invention, a preform for a container is provided, comprising a coating layer applied using the method described herein. A container is also provided comprising a coating layer that can be obtained by stretching a preform as described herein. The coating layer is applied to a preform for a container using a low-energy atmospheric plasma discharge, resulting in a coating layer that is preferably cross-linked and / or covalently grafted onto the preform surface. Remarkably, the coating layer remains intact during blow molding, i.e., the stretching of the preform into a container. Very thin coating layers can be achieved using the method described herein. Another aspect of the invention is the use of plasma deposition in the production of a container comprising a coating layer. More specifically, the present invention seeks to improve the containers or preforms thereof in one or more of the following aspects: - improvement in view of the release properties (in the case of a bag-in-can), i.e., delamination of the inner layer from the outer layer, meaning that the delamination of the inner layer from the outer layer before, during, or after the container forming stage (such as a stretch blow molding stage) is improved and controlled as much as possible; - improvement in terms of moisture absorption, which leads, for example, to a longer storage life of the containers or their preforms; - Improvement in heat transfer to the preform. This improves the forming of the container from the preform; - Improved colorability. This makes it possible to apply color uniformly or in a localized area to a container; - Improved printability. This allows direct printing onto a container using well-established printing techniques; LAnann / zznz / E / YiAi - improvement in terms of gas permeability. In particular, with regard to the unwanted escape of carbon dioxide, which is an important component of many beverages, such as beer, and with regard to the unwanted entry of oxygen (O2), for example, from the surrounding air, which can result in unwanted degradation of the contained fluid; - Improved light transmission properties (visible or ultraviolet (UV) light). This prevents undesirable reactions to the contents of the containers, such as the beer glowing. Brief description of the drawings Figure 1 is a schematic representation of a preform for a container according to the invention. Figure 2 is a schematic representation of a container according to the invention. Figure 3 shows an example of TOF-SIMS (time-of-flight secondary ion mass spectrometry) analysis on a PET preform, onto which a coating layer according to the invention is applied in the upper half of the analyzed area. The detected ions are representative of the coating layer. Figure 4 shows an example of TOF-SIMS analysis on a PET preform, onto which a coating layer according to the invention is applied to the upper half of the analyzed area. The detected ions are representative of PET. Figure 5 shows an example of TOF-SIMS analysis on a container, which was produced by blow molding a preform with a coating layer according to the invention applied thereto. The detected ions are representative of the coating layer. Detailed description of the invention According to the invention, a method is provided for applying a coating layer onto a preform for a container, said method comprising the steps of: a) provide a cold, low-energy plasma; b) exposing the coating precursors and the preform to said plasma, thereby chemically activating the precursors, the preform, or both; c) depositing a coating layer on at least part of the preform by reaction of the activated precursors with each other and / or with the activated preform. A method for producing a container is also provided, which method comprises the method for applying a coating layer as described herein, followed by a stretching step. A low-energy plasma is defined herein as a plasma whose power density is high enough to activate the precursors and / or the preform, allowing a chemical reaction to take place, but low enough to prevent the destruction of the precursors. LAnann / zznz / E / YiAi preform and / or the container. The power density may be in the range of 0.2–8 W / dm³, more preferably between 0.5 W / dm³ and 7 W / dm³, even more preferably between 0.8 W / dm³ and 6 W / dm³, even more preferably between 1 W / dm³ and 5 W / dm³, even more preferably between 1.5 W / dm³ and 4 W / dm³, even more preferably between 2 W / dm³ and 3 W / dm³, such as 2 W / dm³, 2.1 W / dm³, 2.2 W / dm³, 2.3 W / dm³, 2.4 W / dm³, 2.5 W / dm³, 2.6 W / dm³, 2.7 W / dm³, 2.8 W / dm³, 2.9 W / dm³, 3 W / dm³, or any intermediate value, most preferably in the range of 2.4 W / dm3 to 2.6 W / dm3. A cold plasma is defined herein as a plasma whose temperature is sufficiently low to avoid melting or otherwise damaging the precursor and / or preform exposed to it. The plasma temperature may be 150°C or lower, preferably 130°C or lower, more preferably 100°C or lower, even more preferably 70°C or lower, even more preferably 60°C or lower, even more preferably 55°C or lower, even more preferably 50°C or lower, and even more preferably 45°C or lower. The plasma temperature may be as low as ambient temperature, i.e., the temperature surrounding the plasma. Depending on the location where the coating process takes place, the ambient temperature may be in the range of 10–40°C, preferably 15–30°C, or 20–25°C. The plasma temperature will generally not be lower than ambient temperature.When depositing temperature-sensitive coatings, it is important to maintain a constant plasma temperature at the optimum value. The optimum temperature can be selected depending on the type of precursor or precursor mixture and / or the pressure. Therefore, in one mode, the plasma temperature is selected based on the precursor type, the precursor mixture, and / or the plasma pressure. The plasma of the present invention is preferably an atmospheric plasma having a pressure around ambient pressure. Such plasma is typically created and discharged at a pressure between 400 and 1600 hPa, preferably between 450 and 1400 hPa, more preferably between 500 and 1300 hPa, more preferably between 600 and 1250 hPa, more preferably between 700 and 1200 hPa, more preferably between 800 and 1150 hPa, but most preferably between 900 and 1100 hPa, most preferably around ambient pressure, which is typically around 1013 hPa. The plasma pressure can play an important role in the quality of the deposited layer. Some plasma precursors are sensitive to plasma pressures that are too low and / or too high compared to atmospheric pressure, while other precursors provide better coating at lower or higher plasma pressures.However, low-energy cold plasma can typically be applied at reduced pressures of less than 400 hPa down to a vacuum, or at increased pressures of more than 1600 hPa; both types require pressure deposition to maintain such low or high pressures. Using plasma at pressures within the currently preferred range around ambient pressure reduces costs and related difficulties. LAnann / zznz / E / YiAi with the maintenance of pressure differences and pressure gradients. A plasma with the conditions described above can be called soft plasma. Soft plasma can provide sufficient energy to activate the precursors, the preform, or both. This allows reactions, such as polymerization reactions, to occur between the activated precursors, as well as between the activated precursors and the activated preform. At the same time, the conditions are mild enough to prevent the destruction and / or loss of the precursors' chemical function. Therefore, a wide range of precursors can be used in the production of the coating layer. Even sensitive precursors, such as antibodies, can be activated using cold, soft, i.e., low-energy plasma. Plasma can be generated using a dielectric barrier discharge (DBD plasma), preferably under atmospheric conditions. A coating layer, as described herein, is defined as a layer of material of a different composition than the substrate on which it is deposited, i.e., the preform of a container. The plasma chemically activates at least one of the precursors and / or the preform for the container. This activation of the precursors and / or the preform can occur through the opening of molecular double bonds, the elimination of radicals, and / or the formation of ions. This enables and / or enhances the reactions required to form the coating layer. These reactions may involve: - reactions between precursors, such as polymerization reactions and crosslinking reactions, and / or - reactions between the precursors and the preform for the container, such as covalent bonding reactions. This allows reactions, such as polymerization reactions, to take place between the activated precursors, as well as between the activated precursors and the activated preform or container. Preferably, the coating layer is covalently bonded to the surface. Preferably, the coating layer comprises crosslinks and covalent bonds with the preform or container. Such crosslinks and covalent bonds are believed to be responsible for, or at least enhance, the structural integrity of the coating. If the coating is applied to a preform that is subsequently enlarged in the process, for example, by stretch blow molding, the crosslinks and covalent bonds between the coating layer and the preform prevent damage to the coating layer, even when the preform is stretched. Using the method as described herein, the coating layer remains intact when the preform is stretched, for example, during blow molding, which includes LAnann / zznz / E / YiAi using a thin coating layer, which does not give the preform the impression that it is defective or contaminated. In one embodiment of the invention, the precursors comprise one of the suitable precursors listed above. However, in other embodiments, the precursors comprise two or more of the suitable precursors listed above. In a preferred embodiment, a method is provided in which the coating layer is created using at least two precursors, wherein at least one of said precursors is suitable to act as a light barrier, specifically against ultraviolet (UV) and visible light. By combining at least two precursors, the coating layer can have more than one functionality, such as reduced moisture absorption as well as UV / visible light protection. Furthermore, or alternatively, combining two or more precursors can lead to enhanced functionalities, such as achieving an even greater reduction in the moisture absorption coefficient, which could result in moisture absorption coefficients as low as 0.030% by weight per week or less, in relation to the weight of the preform. The coating layer can act as a barrier against gases. Preferably, the coating layer acts as a barrier against oxygen (O₂) and / or carbon dioxide (CO₂). The migration of gases such as O₂ into a container can lead to the degradation of the container's contents. The outward migration of gases such as CO₂ can also lead to a decrease in the quality of the contents, for example, in the case of carbonated beverages. In a preferred embodiment of the invention, the coating layer imparts one or more functionalities to the preform for a container. Since the coating layer remains intact when the preform is stretched into a container, the functionalities imparted by the coating layer can be present both in the preform before stretching and in the container after the stretching step. Such functionalities can be related to one or more of the following properties: - surface tension properties, which can result in, for example, hydrophobicity, reduced moisture absorption, improved release properties, improved slip properties, improved release of viscous liquids and / or improved surface printability; - barrier properties, against, for example, permeation of gases, such as O2 and / or CO2, as well as against other unwanted chemicals; - optical properties, for example, addition of color or fluorescence, and / or provision of a barrier against ultraviolet or visible light; - reheating properties; - preform strength, for example, improved stress cracking resistance. The functionality of the coating layer is determined, at least partially, by the type LAnann / zznz / E / YiAi of precursors used to manufacture the coating layer. Table 1 summarizes which types of precursors and / or specific precursors can be used to impart certain functionalities, as observed in the inventors' experiments. Table 1 LAnann / zznz / E / YiAi Functionality Precursor Types Tested Precursors a. Reduced moisture absorption Fluorocarbons, siloxanes, fatty acids, hydrocarbons perfluorodecanoic acid (PFDA), hcxamtyldisiloxane (HMDSO), tetraethyl orthosilicate (TEOS), vinyltriethoxysilane (VEOS), tetra-vinyl-tetramethylcyclotetrasiloxane (V4D4), nonanoic acid, nonene, dodecane b. Improved internal and external preform delamination Fluorocarbons, siloxanes, polymer solutions PFDA, ethylene vinyl alcohol (EVOH) c. Improved reheating properties Metal nanoparticles, carbon nanoparticles, conductive polymers Au, carbon nanotubes (CNTs), polyaniline, polythiophene d.Improved slip properties Fluorocarbons, siloxanes, glycols, hydrocarbons, fatty acids PFDA, HMDSO, poly(ethylene glycol) methyl ether acrylate (PEGMEA), di(ethylene glycol) ethyl ether acrylate (DEGEA). Functionality Precursor Types Proven Precursors e. Added color and / or other optical properties Acrylic inks, UV tracer solutions acrylic inks (e.g., available in STS™), rhodamine, tartrazine, fluorescein, uranine (e.g., available in Radiant™ UV markers) f. Improved CO2 barrier properties Siloxanes, polymer solutions HMDSO, VEOS, EVOH g. Improved O₂ barrier properties Siloxanes, polymer solutions HMDSO, VEOS, V4D4, EVOH h. Improved light barrier properties UV light absorbers, conjugated aromatic molecules, hindered amine light stabilizers, inorganic oxides T1O2, Tinuvin® light stabilizers i. Limited migration of unwanted chemicals arising in the preform material to the container contents Siloxanes HMDSO j. Improved internal non-stick properties Fluorocarbons, glycols PFDA, PEGMEA, CAS 116143, CAS 116-15-4, DEGEA k.Improved direct object printability Acrylates, methacrylates, hydroxyl groups, epoxy groups AA, methyl methacrylate (MMA), hydroxyethyl methacrylate (HEMA), HEAA, glycidyl methacrylate (GLYMA) 1. Improved stress crack resistance Polymer solutions, siloxanes EVOH, HMDSO, vinyl methoxysiloxane (VMOS), PFDA, nonene. LAnann / zznz / E / YiAi The different functionalities that the coating layer can impart are described in more detail below. a. Reduced moisture absorption One function of a coating layer can be to reduce the rate of moisture absorption of a coated preform, before increasing the preform to a full-size container, for example, by blow and stretch molding. When a preform surface is coated, the plasma-deposited coating layer can result in a preform with improved stretch blow molding capabilities compared to currently used methods. Reproducibility is extremely important in a production process. Improved stretch blow molding capabilities allow for increased reproducibility in the production of plastic containers from preforms. As mentioned earlier, the coating layer can reduce the rate of moisture absorption, thus improving the preform's shelf life. The increased storage time is advantageous for several reasons. The production of containers from preforms, where the preforms are produced in a separate process, can be hampered by many different factors, such as machine breakdowns, national holidays that force the factory to close for one or more weeks, or employee strikes. Furthermore, the preforms may need to be transported long distances with extended transit times, for example, via overseas shipments. In such cases, preforms nearing their expiration date could already be past their expiration date by the time the containers are produced from them.Therefore, both the time and profitability of the entire production process can be reduced. In many cases, these problems could be avoided with a proper management system. However, in some cases, for example, due to unforeseen circumstances, mismanagement, or human error, the expiration of preforms is unavoidable. In these cases, it would be advantageous to increase the shelf life of the preforms. Improving the shelf life of preforms could also unlock or strengthen the possibility of producing preforms in locations other than those used for the production of plastic containers. This could be especially advantageous if, for some reason, preform production is located on the other side of the world compared to container production.Furthermore, the increased shelf life of the preform improves the feasibility of having different manufacturers produce the preforms and the containers. This could be economically advantageous and / or beneficial for technological development. Separating manufacturers can lead to improved and / or faster development of the manufacturing process. Since preforms tend to be significantly smaller than containers, transporting preforms is easier and less expensive than transporting containers. Therefore, it tends to be more cost-effective to produce preforms in a single facility. LAnann / zznz / E / YiAi specialized and transport these preforms to a second facility where the containers are produced, and possibly also filled and prepared for consumption. The rate of moisture absorption can be significantly reduced by treating only a portion of the preform's surface. For example, treating only the outer surface could reduce the absorption rate by approximately half, and sealing the preforms from the environment could reduce it by a factor of 10 or more. In a preferred embodiment, the preform has a moisture absorption coefficient of less than 0.070% by weight per week relative to the weight of the preform, preferably less than 0.050% by weight per week relative to the weight of the preform, even more preferably less than 0.040% by weight per week relative to the weight of the preform, and most preferably less than 0.030% by weight per week relative to the weight of the preform. Currently available methods for reducing the moisture absorption rate result in a preform with a moisture absorption coefficient greater than 0.070% by weight per week relative to the weight of the preform. To increase the service life of the preform, the inventors have found that the moisture absorption coefficient should be less than 0.070% by weight per week relative to the weight of the preform. A moisture absorption coefficient of less than 0.070% by weight per week relative to the weight of the preform is desirable.A decrease of 0.50% by weight per week relative to the weight of the preform further increases the preform's shelf life. The present inventors have noted that by decreasing the moisture absorption coefficient to below 0.070% by weight per week relative to the weight of the preform, the preform's shelf life increased by a minimum of four weeks. Further reduction of the moisture absorption coefficient resulted in an even greater minimum increase in shelf life. The present inventors noted that reducing the moisture absorption coefficient to below 0.030% by weight per week relative to the weight of the preform increased the shelf life by more than twelve weeks. In one embodiment, the precursors comprise fluorocarbons, siloxanes, fatty acids and / or hydrocarbons, or any combination thereof, preferably PFDA, HMDSO, TEOS, VEOS, V4D4, nonanoic acid, nonene, dodecane, or any combination thereof. A reduction in the moisture absorption rate has been experimentally observed for such precursors. b. Enhanced delamination of the inner and outer layers This is particularly important in the feeding of stretch-spread molding, for example, when making a bag in a container. In one embodiment, the precursors comprise fluorocarbons, siloxanes, polymer solutions, or any combination thereof, preferably PFDA, EVOH, or any combination thereof. Enhanced delamination has been experimentally observed for such precursors. LAnann / zznz / E / YiAi c. Improved reheating properties This is particularly important for improving the processability of stretch and blow molding. In one embodiment, the precursors comprise metallic nanoparticles, carbon nanoparticles, conductive polymers, or any combination thereof, preferably Au, CNT, polyaniline, polythiophene, or any combination thereof. Enhanced heat absorption has been experimentally observed for such precursors. d. Improved slip properties This is particularly important for improving processes where preforms and / or containers are transported, for example, a filling line. In one embodiment, the precursors comprise fluorocarbons, siloxanes, glycols, hydrocarbons, fatty acids, or any combination thereof, preferably PFDA, HMDSO, PEGMEA, DEGEA, or any combination thereof. Improved slippage between containers has been experimentally observed for such precursors. e. Added color and / or other optical properties This is particularly important for traceability, combating counterfeiting, or other desired functions. In one embodiment, the precursors comprise one or more acrylic inks, UV tracer solutions, or any combination thereof, preferably STS inks, radiant UV tracers, or any combination thereof. A mild coloration of the preform or container for such precursors has been experimentally observed. f. Improved CO2 barrier properties In one embodiment, the precursors comprise siloxanes, polymer solutions, or any combination thereof, preferably HMDSO, VEOS, EVOH, or any combination thereof. Improved CO2 barrier properties have been experimentally observed for such precursors. g. Improved barrier properties of O₂ In one embodiment, the precursors comprise siloxanes, polymer solution, or any combination thereof, preferably HMDSO, VEOS, V4D4, EVOH, or any combination thereof. Improved O2 barriers have been experimentally observed for such precursors. h. Improved light barrier properties This is particularly important in the face of visible light and / or UV light. In one embodiment, the precursors comprise UV light absorbers, conjugated aromatic molecules, hindered amine light stabilizers, inorganic oxides, or any combination thereof. LAnann / zznz / E / YiAi themselves, preferably TiCh, Tinuvin® families, or any combination thereof. Improved light barriers have been experimentally observed for such precursors. i. Limited migration of unwanted chemicals arising in the preform material to the container contents Unwanted chemicals can migrate from the container material into the liquid inside, such as the formation of acetaldehyde in PET materials, which could alter the odor and taste of the liquid contents. In this regard, the present invention also aims to provide removal functionalities. In one embodiment, the precursors comprise siloxanes or any combination thereof, preferably HMDSO or any combination thereof. Limited migration of undesirable chemicals has been experimentally observed with such precursors. j. Improved internal non-stick properties This is particularly important for the easy release of viscous products such as mayonnaise, ketchup, syrups, etc., so the coating is applied at least to the inner surface of the preform and / or the container. In one embodiment, the precursors comprise fluorocarbons, glycols, or any combination thereof, preferably PFDA, PEGMEA, CAS 116-143, CAS 116-15-4, DEGEA, or any combination thereof. Internal anti-adherence has been experimentally observed for such precursors. k. Improved direct object printability In one embodiment, the precursors comprise acrylates, methacrylates, hydroxyl groups, epoxy groups, or any combination thereof, preferably AA, MMA, HEMA, HEAA, GLYMA, or any combination thereof. Improved direct printing has been experimentally observed for such precursors. 1. Improved resistance to stress cracking In one embodiment, the precursors comprise polymer solutions, siloxanes, or any combination thereof, preferably EVOH, HMDSO, VMOS, PFDA, nonene, or any combination thereof. Improved tensile crack resistance has been experimentally observed for such precursors. The aforementioned functionalities may be desired for the entire preform or container, but they may also be desired or required only for a portion of the preform or container. Furthermore, it may be desirable for different portions of the container to have different functionalities, or a different combination of functionalities. Therefore, in the embodiments of the present invention, different coatings may be applied to different portions of the preform and / or container. In other embodiments, LAnann / zznz / E / YiAi The plasma coating can be deposited on at least one section or on the entire surface of the preform. Different precursors can be deposited using a layer-by-layer deposition strategy, in which each successive deposition stage deposits a precursor as a layer onto at least a section or the entire surface of the preform. Another possibility involves depositing one or more layers comprising a mixture of different precursors, whereby deposition is achieved by introducing the different precursors simultaneously into the plasma. A person skilled in the art will note that any combination of the deposition possibilities mentioned herein could be applied to obtain a coating with at least two different precursors. The functionality of the coating layer can depend significantly on the conditions, such as temperature and pressure, under which the coating layer is deposited. To achieve good functionality, it is important to work under optimal conditions, which may vary for each precursor used, although always within the preferred ranges specified in this document. In addition, a preform for a container is provided, comprising a coating layer applied using the method described herein. Preferably, the preform comprises a coating layer that can be obtained by the method described herein. Preferably, the coating layer that is applied using and / or can be obtained by the method described herein is cross-linked. Additionally or alternatively, the coating layer that is applied using and / or can be obtained by the method as described herein is covalently grafted onto the preform for a bag-in-a-container. A container comprising a coating layer is also provided, obtainable by stretching the preform as described herein. In one embodiment of the invention, the container can be obtained by blow molding the preform. The use of plasma deposition to apply a coating layer for, for example, reducing moisture absorption provides a means of controlling the coating deposition process down to nanoscale precision. Thickness control is important because deposition of too thick a layer could result in a visibly visible coating. Visibly visible coatings could give the impression of a defective or contaminated preform and, as such, are undesirable. Note that, in the context of this document, the coating may produce visible effects such as coloration or a smooth appearance. However, it is an advantage of the present invention that such effects do not appear to be the result of a coating. LAnann / zznz / E / YiAi The coating layer deposited on the preform can have a thickness of between 5 and 600 nm, preferably between 5 and 500 nm, more preferably between 10 and 500 nm, even more preferably between 10 and 300 nm, even more preferably between 10 and 200 nm, and still more preferably between 10 and 80 nm, such as 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, or any value in between, most preferably around 20 nm. The thickness of the plasma coating can be effectively controlled by controlling the exposure time of the preform or the container to the plasma and / or precursors. In one embodiment of the invention, the container can be obtained by integrally stretching the preform, wherein the stretch ratio is from 2 to 20. Preferably, the stretch ratio with respect to volume is between 5 and 20, more preferably between 10 and 15, even more preferably between 12 and 15, such as 12, 13, 14, 15 or any value between them, most preferably around 13.5. Preferably, said preform increases in length with a stretch ratio of 2 to 20, preferably 3 to 15, more preferably 4 to 12, even more preferably 5 to 10, and / or said preform increases in diameter with a stretch ratio of 2 to 20, preferably 3 to 15, more preferably 4 to 12, even more preferably 5 to 10. During the stage of increasing the size of the preform, the length, diameter and / or volume are increased according to the intervals mentioned above.The thickness of the coating layer decreases with increasing stretch ratio. It is believed that the coating thickness on the preform decreases inversely proportional to the increase in surface area. Since the shape of the preform can change during sizing, the theoretical inverse proportionality of the thickness reduction to the volume stretch ratio to the power of 2 / 3 does not necessarily hold. Preferably, thermoplastic preforms are stretched in both length and diameter during integral stretching. After stretching, the coating layer on the container may be 100 nm thick or less. Preferably, the coating layer is 80 nm thick or less, more preferably 50 nm thick or less, such as 20 nm thick or less. The thickness of the coating layer after stretching may be as low as 5 nm, but is preferably greater. In one embodiment, the thickness of the coating layer on the container is 30 nm thick or less, more preferably 25 nm thick or less, even more preferably 20 nm thick or less, even more preferably 15 nm thick or less, and even more preferably 10 nm thick or less, such as 10 nm, 9 nm, 8 nm, 7 nm, 6 nm, 5 nm, 4 nm, 3 nm, 2 nm, 1 nm, or any intermediate value, most preferably around 6 nm. Preferably, the coating on the container is at least 2 nm thick. Due to the low thickness of the coating layer, only a small fraction (e.g., less than 1% by weight) of the total amount of material in the preforms and containers according to the invention is coating material. Because of this, the coated preforms and containers are LAnann / zznz / E / YiAi can be recycled well, without negatively affecting the quality of the recycled material. In certain embodiments, the preform may be a preform for a bag-in-a-container, comprising an inner preform and an outer preform with opposing surfaces, wherein at least one of the opposing surfaces is coated with a coating layer applied using the method described herein. In that case, the coating layer may be applied to one or more of the following surfaces: the inside of the inner preform, the outside of the inner preform, the inside of the outer preform, and the outside of the outer preform. Preferably, the coating layer is applied at least to the outside of the inner preform, the inside of the outer preform, or both. In principle, the coating layer may be applied to a portion of these surfaces, or to all of them. Preferably, the coating layer is applied to all of the surfaces.Thus, the surface properties of the inner and / or outer surfaces of the preform or the container on which the coating layer is applied are determined primarily by the properties of the coating layer. Preferably, the coating layer is intact. An intact coating layer is defined as one that covers the entire surface to which it was applied. Therefore, the coating layer has no regions where the underlying surface material is exposed. Thus, the surface properties, such as delamination properties, of the preform or the container to which the coating layer is applied are determined by the properties of the coating layer. Preferably, the coating layer remains intact during preform stretching, resulting in an intact coating layer on the container. To confirm the presence of the intact coating layer with a thickness according to the invention, surface techniques such as time-of-flight secondary ion mass spectrometry (TOF-SIMS) can be applied, as shown in Figures 3-5. According to the invention, the coating layer is applied to at least a portion of the surface. Depending on the application, certain parts of the surface may be intentionally left uncoated. For example, if delamination properties need to be improved, it is not necessary to coat the neck portion of a preform that will be used to prepare the bag in the container, since this neck portion does not normally deform during blow molding. Alternative methods for characterizing the coating layer may include optical measurements. Since a wide variety of precursors can be used to form the coating layer, optically active components such as pigments or dyes can also be incorporated into it. These optically active components can be detected using methods of Optical detection. For example, when fluorescent materials are incorporated into the coating layer, the presence of an intact coating layer can be demonstrated by fluorescence measurements. In a preferred embodiment, a coloring agent such as a pigment or dye is added to the plasma, preferably as a gas or liquid, or as a powder dissolved in a liquid or colloidal mixtures in aerosol form. The coloring allows for easier quality control by visual inspection, but it can also be used for other visual effects. For example, when fluorescent materials are incorporated into the coating layer, the presence of an intact coating layer can be demonstrated by fluorescence measurements.Additionally, if the intention is to provide a direct print on the container later, supplying the coloring agent and plasma can provide a more uniform background color in an easier and faster way than a coloring process over the coating. Preferably, the coating layer is a conformal coating layer. Such a conformal coating closely follows the surface, even if the surface includes large curves, for example, near an opening, near a neck, or near the bottom of the preform or container. In the case of a preform for a bag-in-a-container, the inner and outer preforms can be made of the same or different materials. The coating layer applied to the outside of the inner and / or inside of the outer preform can prevent contact between the material of the inner and outer preforms. In this case, the same material of the inner and outer preforms will not be in contact. However, when the coating layer is present on at least one of the opposing surfaces, the delamination properties depend on the interaction between the coating layer and the other opposing surface, or on the interaction between the two coating layers. In this way, the coating layer can optimize the delamination of the inner and outer layers, for example, before, during, and / or after blow molding. In the case of a preform composed of multiple preforms, for example, a preform for a container bag, such a preform can be formed by joining two or more overlapping preforms, i.e., an inner and an outer preform, using methods known in the field. Non-limiting examples of such methods include rotational welding of the inner and outer preforms, as described, for example, in document EP2885241. To achieve the joining of the preforms, there may be regions, such as the neck region, where contact between the inner and outer preforms is deliberately established. It should be noted that a preform for a container bag in which the same material of the inner and outer preforms is not in contact with each other, as described above, does not preclude contact between the inner and outer preforms. LAnann / zznz / E / YiAi deliberately in specific regions such as the neck region of the preform for a bag in a container, to achieve the required structural integrity. Figure 1 is a schematic representation of a cross-section of a container preform according to the invention. With reference to Figure 1, a container preform (1) is provided, comprising a coating layer (2). In Figure 1, the coating layer is present on the exterior of the preform. Alternatively, or in addition, the coating layer may be present on the interior of the preform. Figure 2 is a schematic representation of a cross-section of a container that can be obtained by blow molding the preform (1), showing the container (3), which comprises a coating layer (4). In Figure 2, the coating layer is present on the outside of the container. Alternatively, or in addition, the coating layer may be present on the inside of the container. In some applications, the coating layer as described herein may have a low surface energy. A coating with a low surface energy can serve various functionalities, including, but not limited to, reduced moisture absorption and improved delamination of the inner and outer layers. A coating layer with a low surface energy may also be referred to as a hydrophobic coating layer. Preforms are often produced in one location and blow-molded into containers in a different location, for example, at the same location where the blow-molded containers are filled. This drastically reduces transport volume compared to transporting the blow-molded containers. However, preforms may have a limited shelf life, and after a certain period, the blow-molding properties of the preform may decline.Preforms with a low surface energy coating have been found to have a longer service life. This also applies to vessels with a hydrophobic coating. Low surface energy and / or hydrophobicity can be expressed in terms of the water contact angle. In a preferred embodiment, the coating layer is hydrophobic. The preferred contact angle may be 90° or greater, preferably 100° or greater, more preferably 120° or greater, such as 150° or greater. When the contact angle with water is 150° or greater, the coating layer may be termed superhydrophobic. In a preferred embodiment, the coating layer is superhydrophobic. Surprisingly, hydrophobic coatings applied according to the present invention do not necessarily result in a color change in the product. Such color changes are commonly observed in other prior art methods for improving shelf life, such as the use of a detergent or the application of a water-resistant coating to the interior and / or exterior surface of a LAnann / zznz / E / YiAi preforma. During bag-in-can operation, a high gas pressure (relative to atmospheric pressure) is typically applied between the outer and inner canisters, causing the fluid to be dispensed from the bag without allowing gas to enter the bag, thus keeping the contents of the canister cool. For proper operation, it is important that the inner canister or bag is delaminated from the outer canister. In a related embodiment of bags in containers, the inner container will be delaminated from the outer container after integral blow molding of the preform for a bag in a container in a controlled manner. Another aspect of the invention is the use of plasma deposition for the production of a container comprising a coating layer. The invention is further described by the following non-limiting examples which further illustrate the invention, and are not intended to limit the scope of the invention and should not be construed as such. Examples Example 1: Coating integrity To test coating homogeneity and integrity, two single-walled preforms were also provided after blow-stretching the preform to a full-size container. These preforms were manufactured by injection molding a combination of PET particles and a silver colorant, resulting in dark gray preforms. This color helped to better detect the coating's effects. Preform 1 was untreated and used as a reference. Preform 2 was treated with a plasma coating according to the invention. During the preform coating process, a green pigment was added to the plasma via an aerosol. Subsequently, the preforms were inflated through the preform opening by stretch blowing to a full-size bottle with a ratio of approximately 11. The reference bottle obtained from preform 1 (bottle 1) showed small defects near the top in the area called the lamello—around the opening, which is a rigid ring or series of rings extending around the periphery of the container and resulting from increased crystallization in the preform—and near the bottom around the injection point of the preform. Both defects are typical of the stretch blow molding process. Bottle 1 had a light grayish color with slight fluctuations in intensity near the two defects. The bottle obtained from preform 2 (bottle 2) showed a uniform light green color and The color is uniform throughout the bottle (except for similar intensity fluctuations near defects). The homogeneous light green color of bottle 2 indicates that the coating remains intact after inflating the preform to a volume ratio of up to 11. The color pigment is well distributed throughout the bottle, and the coating adheres very well to the entire surface of the preform and the bottle. Example 2: surface energy The coating of the preform and the resulting container can serve multiple purposes. It can, for example, act as a moisture barrier, preventing preform degradation during storage. It can also act as a moisture barrier for the container. Other effects include providing color (by adding a pigment, for example, to the plasma as demonstrated in the previous example). A non-stick coating can also be applied according to the present invention, ensuring that an inner container easily delaminates from an outer container of a double-walled container (e.g., bag in container). Delamination is greatly reduced by lowering the surface energy. Release is also better controlled at a predetermined pressure level. However, uncoated plasma treatments tend to increase surface energy. The inventors have found that, nevertheless, surface energy is reduced if at least one precursor is administered in a plasma as a gas or liquid aerosol. To test the reduction of surface energy, two preforms were prepared, both composed of PET with a silver dye to provide an easy background color when using a feather test described below. Preform 1 remained untreated, while preform 2 received a coating according to the present invention. The surface energy of the preforms was tested using a set of test pens with different types of ink, each ink type having well-calibrated surface energies. If the surface energy of the substrate is equal to or greater than the surface energy of the ink, the ink will spread across the surface, resulting in smooth, uniform coloring. If the surface energy of the substrate is less than the surface energy of the ink, the ink will clump together into non-homogeneous droplets. Both preforms were subjected to three test feathers, with surface energies of 34 mN / m, 38 mN / m, and 44 mN / m, respectively. The untreated preform 1 was found to have a surface energy between 38 and 44 mN / m, consistent with the general assumption that PET has a surface energy between 40 and 50 mN / m, making it difficult to paint and requiring more force for delamination. LAnann / zznz / E / YiAi The treated preform had a surface energy of less than 34 mN / m, which resulted in improved delamination when used, for example, in a double-walled container (such as a bag-in-a-can). This example shows that surface energy can be reduced using a plasma with five precursors. However, the inventors have also noted that certain types of precursors can increase the surface energy of the coated surface. Such a higher surface energy may be preferable for achieving other functionalities, in particular, improving direct printability (resulting in accurate, high-quality printed images).

Claims

1. A method for applying a coating layer onto a preform for a container, the method comprising the steps of: a) providing a low-energy cold plasma; b) exposing the coating precursors and the preform to said plasma, thereby chemically activating the precursors, the preform, or both; c) depositing a coating layer onto at least a portion of the preform by reaction of the activated precursors with each other and / or with the activated preform.

2. Method according to claim 1, wherein the coating layer is covalently grafted onto the preform.

3. Method according to claim 1 or 2, wherein the coating layer is cross-linked, such that the layer remains intact when the preform is stretched.

4. Method according to any of claims 1-3, wherein the preform comprises a thermoplastic material.

5. Method according to claim 4, wherein the thermoplastic material comprises one or more selected from the group consisting of PET, PLA, PEF, PEN, PP and PE.

6. Method according to any of claims 1-5, wherein the coating layer provides the preform with hydrophobic properties.

7. Method according to claim 6, wherein said hydrophobic properties are imparted by a coating layer derived from a first precursor comprising fluoroacrylate monomers, fluoroalkyl acrylate monomers, fluoromethacrylate monomers, fluoroalkyl methacrylate monomers, fluorosilane monomers or a combination or derivatives thereof, and a second precursor comprising cyclosiloxanes.

8. Method according to any of claims 1-7, wherein the plasma is atmospheric.

9. Method according to any of the preceding claims wherein the coating layer is applied over the entire surface of said preform.

10. Method for producing a container, wherein the method comprises the method according to any of claims 1-9, followed by a stretching step.

11. Preform for a container, comprising a coating layer applied using the method according to any of claims 1-9.

12. Container comprising a coating layer obtainable by stretching the preform according to claim 11. LAnann / zznz / E / YiAi 13. Container according to claim 12 obtainable by blow molding of the preform.

14. Container according to claim 12 or 13, wherein the stretch ratio of the blow-molded container is 5-20.5 15. Container according to any of claims 12-14, wherein the coating layer is intact.

16. Use of plasma deposition using a low-energy cold plasma for the production of a container comprising a coating layer.