Transfer film, and method for transferring a barrier layer onto a substrate

Abstract

The present invention relates to a transfer film for applying a barrier layer onto a substrate. The transfer film comprises a carrier film, on which a layer sequence is applied consisting of at least one lacquer layer, made of a barrier lacquer, and an inorganic layer, wherein the adhesive forces between the lacquer layer and the carrier film are lower than the adhesive forces between the lacquer layer and the inorganic layer. The transfer film is characterised in that the barrier lacquer comprises a polymer matrix having a hydrophilic component and a hydrophobic component, of which the hydrophilic component significantly outweighs the hydrophobic component. The transfer film allows a barrier layer having effective barrier properties to be transferred onto target substrates, for which this was previously technically impossible or economically unsuitable.

Description

[0001] Transfer film and method for transferring a

[0002] Barrier layer on a substrate

[0003] Field of the invention

[0004] The present invention relates to a composite film, hereinafter also referred to as a transfer film, and to a method for transferring a barrier layer to another substrate. The composite film comprises a carrier film on which a layer sequence consisting of a barrier lacquer and an inorganic layer, also referred to as metallization, is applied. The composite film is suitable for transferring the barrier properties of the combination of barrier lacquer and inorganic layer against oxygen, water vapor, and other organic substances to another substrate, such as paper or cardboard, using a transfer process.

[0005] A technically obvious area in which such a film can be used is, for example, but not exclusively, the area of ​​food packaging.

[0006] State of the art

[0007] An important function of food packaging is to protect the packaged goods from environmental influences that promote spoilage, such as oxygen, water vapor, or light. To ensure this protective function and thus a long shelf life for the food, materials that provide a barrier effect against these environmental influences are often used in packaging. Typically, desired permeation values ​​for sensitive foods (e.g., meat, fish) are < 5 cm. 3 / (m 2 d bar) at 23 °C and 50 % relative humidity to oxygen and <10 g / (m 2 d) at 23 °C and 85 % relative humidity compared to water vapor.

[0008] An established method for creating a barrier in the film sector is the vacuum deposition of thin inorganic layers (aluminum, aluminum oxide, silicon oxide) using physical vapor deposition (PVD). In this process, the inorganic material is evaporated in a high vacuum, e.g., using an ion beam or thermal boat evaporation. The evaporated material then condenses on the substrate film, forming a continuous, nanoscale (nm-scale) layer. This significantly improves the basic barrier of the substrate; typical barrier improvement factors (BIF) of up to 10 (relative to the substrate) are used.

[0009] However, the PVD process places high demands on the substrate (e.g. low roughness), so that only certain plastic films such as biaxially oriented polypropylene (PP-BO), biaxially oriented polyethylene (PE-BO), biaxially oriented polyethylene terephthalate (PET-BO), rarely also polyethylene (PE) or oriented polyamide (OPA) are used.

[0010] Vacuum deposition of fiber-based substrates (paper, cardboard) is particularly difficult and is generally used for optical purposes rather than to create a barrier layer. A major problem, alongside roughness, is the water content of paper substrates. This would outgas in the vacuum required in the PVD process, making it more difficult to create the necessary vacuum and also preventing the formation of a closed barrier layer. The paper must therefore be dried before the deposition process. This water must be reintroduced into the paper after vacuum deposition (parallel to the topcoating process) (usually by wetting the back of the paper using a gravure application process). However, the paper shrinks in width during drying (fibers release water), whereas when remoistened it swells and becomes wider again.The paint layer stretches, the metallization cracks and loses its barrier properties.

[0011] Only through intensive investigations have special systems of paper and barrier coatings been identified that, under conditions specifically adapted to this process, have succeeded in improving the barrier properties of a few paper types (low hygroexpansion, low roughness, low water absorption of the coated side) with barrier coatings through metallization. This process is severely limited both by the choice of paper and by the process conditions, and even slight deviations in the process lead to failure (extremely narrow process window).

[0012] For this reason, vacuum deposition of paper substrates to create barrier properties is still not established industrially. Instead, to achieve comparable barrier properties, the paper is usually laminated to a micron-scale aluminum foil. This is significantly more expensive and also has disadvantages in terms of sustainability.

[0013] Transfer metallization of fiber-based substrates is another well-known process and is primarily used for decorative purposes, as it can produce particularly glossy surfaces for the packaging of high-quality products (spirits, perfumes, etc.).

[0014] This process is primarily used for cardboard packaging, where, above a certain grammage (approx. 120 g / m 2) vacuum evaporation can no longer be used because too much water is released into the vacuum chamber and therefore the required negative pressure cannot be built up.

[0015] In transfer metallization, a plastic film is coated with a release coating and then metallized using PVD. This film is laminated to the cardboard using an adhesive and delaminated at the point between the release coating and the plastic film, leaving the metallization on the cardboard. During the process of lamination to the cardboard and the delamination of the plastic film, forces are exerted that lead to microcracks in the metal layer, so that it no longer has any barrier properties. Therefore, no barrier effect has been achieved with this process to date.

[0016] Numerous transfer metallization processes and their products are described in the patent literature. US Pat. No. 4,344,998 describes a metallized composite structure and the process for its production. However, this variant focuses on the optical and thermal properties. A barrier function or applicability to technically challenging target substrates such as paper or biopolymers is not described here.

[0017] A transfer film according to the preamble of claim 1 is described in EP 0034392 B1. The barrier lacquer used in this transfer film consists of copolymers of PVC or an acrylic copolymer.

[0018] DE 102019114198 A1 describes a metallized barrier paper, which is also obtained by transfer metallization. The transfer foil used for this purpose is not specified in detail.

[0019] NL 9200945 A describes various methods for producing a flexible, plastic-based packaging material with barrier properties. However, this involves coating a composite film component (the sealing layer) with an inorganic layer. The transfer of the inorganic layer to another substrate is not mentioned in the patent.

[0020] EP 1585668 A2 describes a metallized packaging material produced by transfer metallization. However, this process uses a very specific process in which the transfer film is first produced by extrusion within the same production line, and then the inorganic layer is directly transferred to the substrate. The properties of the release agent remain largely unmentioned. The goal of the process is to create a decorative glossy layer on cardboard. Nothing is described about the barrier effect of the transferred layer.

[0021] EP 0287083 Bl also describes the decorative finishing of a cardboard laminate and improved resistance to creasing.

[0022] CA 1160552 A1 describes a composite consisting of a paper substrate, an adhesive layer, a thin metal layer, and a lacquer layer, which is produced by transfer metallization. The transfer foil used in the manufacturing process is not further specified.

[0023] US 2017239926 AA describes a special structure of a transfer film in which the release agent consists of a polyvinylamine cross-linked with citric acid.

[0024] US Patent No. 4,250,209 A describes a transfer film consisting of untreated polypropylene, a release agent, and a vapor-deposited metallization layer. The release agent therefore primarily serves to compensate for the inadequate surface quality of the untreated carrier film, enabling the creation of a closed surface in the subsequent metallization step. No special requirements are placed on the coating's barrier properties.

[0025] Problem to be solved by the invention The problem to be solved by the present invention is to provide a transfer film and a method with the aid of which it is possible to transfer a barrier layer onto a target substrate, e.g. paper, with almost no loss, which forms a very good barrier in particular against oxygen and water vapor.

[0026] Description of the invention

[0027] The object is achieved with the transfer film and the method of patent claims 1 and 13. Advantageous embodiments of the transfer film are the subject of the dependent patent claims or can be derived from the following description and the exemplary embodiment.

[0028] The proposed composite or transfer film is formed by a carrier film with a layer sequence applied thereon consisting of a lacquer layer comprising a barrier lacquer and an inorganic layer (also referred to as metallization) on the lacquer layer, wherein the adhesion forces between the lacquer layer and the carrier film are lower than the adhesion forces between the lacquer layer and the inorganic layer. The transfer film is characterized by the barrier lacquer comprising a polymer matrix with a hydrophilic and a hydrophobic portion, of which the hydrophobic portion is in the range of 0.2 - 20%, better 0.5 - 15%, ideally 0.5% - 10%, based on the amount of substance in mol. The hydrophilic portion is at least 70 mol%. The determination of this molar ratio is carried out for thermoplastic lacquer systems using thermal analysis (melting point determination including referencing with

[0029] Monomers; DSC; heating program: 23–300 °C, 10 °C / min heating rate) according to DIN EN ISO 11357-1. For protein-based coatings, the ratio is determined based on the chemical structure (taken from protein databases such as SCOPe) or from the results of GC-MS measurements. Polyester-based coating systems can be analyzed using thermal analysis or GC-MS.

[0030] To produce the transfer film, a plastic-based carrier film is coated with a barrier varnish, e.g. based on polyvinyl alcohol (PVOH), modified polyvinyl alcohol or ethylene-vinyl alcohol (EVOH), for example by extrusion or wet-chemically and then adequately dried. The carrier film can be made of, for example, biaxially oriented (PP-BO), biaxially oriented polyethylene (BO-PE), biaxially oriented polyethylene terephthalate (PET-BO), polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), axially or biaxially oriented polyamide (OPA), polyamide (PA) or another polymer film with sufficient surface quality. A key factor with regard to the varnish properties is that the varnish matrix has both hydrophilic and a low degree of hydrophobic properties. This can be achieved through the chemical properties of the varnish (as a copolymer, blend, or similar).

[0031] The barrier coating is characterized by its predominantly hydrophilic component (at least 70 mol%, preferably at least 80 mol%), preferably hydrophilic monomers (e.g., vinyl alcohol). Hydrophilic monomers in a copolymer exhibit barrier properties against nonpolar substances such as oxygen. A key factor in the selection of the barrier coating is also a certain proportion of hydrophobic functional groups (e.g., ethylene) in the copolymer. Due to their low solubility, these provide a barrier against polar substances (such as water vapor).

[0032] In an advantageous embodiment of the transfer film, a barrier lacquer is used consisting of a copolymer composed predominantly (at least 70 mol%, preferably at least 80 mol%) of hydrophilic monomers. This gives the lacquer intrinsic oxygen barrier properties. The smaller proportion (max. 20 mol%) consists of hydrophobic monomers, which, despite their chemical structure, do not impart intrinsic water vapor barrier properties to the lacquer. Thus, the lacquer to be selected possesses an oxygen barrier but no water vapor barrier. Furthermore, the barrier lacquer is characterized by greater adhesion forces to the inorganic layer than to the carrier film.

[0033] This coated side of the carrier film is then coated with an inorganic layer, for example made of aluminum, aluminum oxide or silicon oxide, using a suitable process.

[0034] Surprisingly, it turns out that the combination of a barrier coating layer and an inorganic layer results in synergistic effects regarding barrier properties that exceed the sum of the barrier properties of the individual layers. The structure of an organic barrier coating and an inorganic coating, especially vapor deposition, means that the low proportion of hydrophobic components in the coating, unlike in the film and coating structure, has an effect, and thus the film, coating, and inorganic layer structure has particularly outstanding barrier properties against both oxygen and water vapor.

[0035] For the transfer of the barrier layer, consisting of the layer sequence of lacquer layer and inorganic layer, to a target substrate, the transfer film is first coated with an adhesive (e.g. polyurethane or hotmelt adhesive) on the inorganic coated side and laminated against the target substrate (e.g. paper, cardboard, biopolymers, etc.), resulting in the following structure:

[0036] Carrier film / barrier coating layer / inorganic layer / adhesive / target substrate.

[0037] The process is particularly advantageous with regard to the barrier properties of the target substrate coated with the barrier layer if the target substrate, rather than the transfer film, is coated with adhesive during the lamination process. This is because the barrier layer (coating layer + inorganic layer) is still relatively sensitive to mechanical stress and contact with solvent-based or water-based adhesives at this stage.

[0038] In a further step, typically during cutting or wrapping of the film / paper composite (with a paper target substrate), the carrier film is separated from the barrier coating layer by the low prevailing adhesion forces and wound separately. Thus, the final product consists of the following structure (shown in reverse order): Target substrate / Adhesive / Inorganic layer / Barrier coating layer

[0039] Surprisingly, it has been shown that the described structure of the transfer film enables a non-destructive transfer of the barrier lacquer layer and the inorganic layer to the target substrate without the use of an additional debonding agent. Thus, even on target substrates that do not normally have sufficient barrier properties (e.g., paper, cardboard, biopolymers, etc.), the desired barrier values ​​against oxygen ( < / = 1 cm 3 / (m 2 d bar) at 23 °C and 50 % RH) and water vapor ( < / = 1 g 3 / (m 2 d) at 23 °C and 85 % RH) to the target substrate.

[0040] Short description of the drawings

[0041] The proposed transfer film and the proposed process are described in more detail below using examples in conjunction with the drawings. Here:

[0042] Fig. 1 shows an exemplary structure of the transfer film;

[0043] Fig. 2 a composite structure between target substrate and transfer film after application of the transfer film, and

[0044] Fig. 3 the finished composite after removing the carrier film.

[0045] Ways to implement the invention

[0046] The present invention describes a transfer film consisting of a carrier film (e.g. PET), a lacquer layer (e.g. EVOH) and an inorganic layer (e.g. made of aluminum, aluminum oxide, silicon oxide, etc.) applied by means of physical vapor deposition (PVD) or comparable processes (e.g. atomic layer deposition (ALD), chemical vapor deposition (CVD)), as shown schematically in Figure 1.

[0047] The barrier coating is preferably applied to the carrier film by extrusion coating or wet-chemical methods. Suitable wet-chemical methods include doctor blade, flexography, roller, spray, dip, nozzle, and curtain coating.

[0048] Suitable carrier films include, for example, biaxially oriented (PP-BO), biaxially oriented polyethylene (BO-PE), biaxially oriented polyethylene terephthalate (PET-BO), polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), axially or biaxially oriented polyamide (OPA), polyamide (PA) or another polymer film.

[0049] In the case of wet-chemical coating, the coating process is followed by a drying step to remove the solvent. Drying can be achieved, for example, by convection, microwave, vacuum, infrared drying, or a combination thereof.

[0050] The formulation used for the coating is based on one or more solvents such as a monohydric alcohol (ethanol, propanol, butanol, etc.), water, an ester (e.g., ethyl acetate), or combinations thereof, as well as a lacquer component. The lacquer component used is characterized by the fact that, after application to the carrier film and drying, it forms a continuous layer. This layer has a good oxygen barrier but only a low water vapor barrier.

[0051] The oxygen permeability (measured according to DIN 53380-3 at 23°C and a relative humidity of 50%) of the paint layer (standardized to a layer thickness of 100 pm) is typically less than 5 cm 3 / (m 2 d bar), better under 2.5 cm 3 / (m 2 d bar), even better under 0.5 cm 3 / (m 2 d bar), ideally less than 0.05 cm 3 / (m 2 d bar) .

[0052] The water vapor permeability (measured according to DIN EN ISO 15106-3 at 23°C and a relative humidity of 85%) of the paint layer (standardized to a layer thickness of 100 pm) is typically below 100 g / (m 2 d) , better under 50 g / (m 2 d) , ideally below 20 g / (m 2 d) , but still above 10 g / (m 2 d) .

[0053] The thickness of the dried coating layer is typically between 5 nm and 100 pm, preferably between 7 nm and 50 pm, even better between 10 nm and 30 pm, and ideally between 10 nm and 10 pm. The coating layer thickness is determined either using a mechanical sensor (as a differential measurement between uncoated and coated carrier film), as a microscopic image of a cross-section taken with a microtome, or as a differential weighing of the basis weight of the coated and uncoated carrier film.

[0054] Particularly suitable coating components are those that are soluble or dispersible in the selected solvent and exhibit the described barrier properties after application to the carrier film. The chemical polymer matrix is ​​essential here. To achieve the desired barrier properties on the target substrate, the polymer matrix has both a hydrophilic and a significantly lower hydrophobic component.

[0055] Examples of polymers with hydrophilic / hydrophobic properties are hydrophobically modified PVOH, EVOH, modified EVOH, medium chain length polyhydroxyalkanoate (mPHA), oligomeric lactic acid (oLA), cutin and its derivatives, as well as combinations thereof.

[0056] The hydrophobic content in the polymer matrix is ​​preferably between 0.5 and 20 mol%, better between 2 and 10 mol% and ideally between 3 and 8 mol%.

[0057] Due to this relatively low proportion of hydrophobic components in the polymer matrix, the barrier coating, when applied to a film substrate, provides a significant barrier to oxygen, but not a sufficient barrier to water vapor for packaging applications. Typically, the barrier coating then exhibits water vapor permeability values ​​of over 10 g / (m²). 2 d) at 23 °C and 85 % relative humidity.

[0058] Surprisingly, however, it turns out that after the application of a nanoscale inorganic layer (e.g., by vacuum deposition) as described below, synergistic effects occur between the lacquer, in particular the hydrophobic lacquer component, and the inorganic coating material. This creates water vapor permeability on the transfer film. < / = 1 g / (m 2d) at 23 °C and 85% RH, which can then be transferred to the target substrate. The water vapor permeability values ​​are standardized to a layer thickness of 100 pm.

[0059] The proportion of the paint component in the coating formulation for applying the paint layer in extrusion coating is ideally more than 70% (m / m), better more than 80% (m / m) and ideally more than 90% (m / m).

[0060] When formulating a wet chemical coating, the proportion of the paint component is usually between 0.1 and 60% (m / m), better between 0.5 and 40% (m / m) and ideally between 1 and 20% (m / m).

[0061] In a next step, one or more inorganic layers, preferably consisting of aluminum (Al), aluminum oxide (AlOx), silicon (Si), silicon oxide (SiOx) or combinations thereof, are applied to the barrier lacquer layer. The inorganic layer is applied using physical vapor deposition (PVD), chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), wet chemical deposition of nanoparticles (such as layered silicates) or other processes that are suitable for depositing nanoscale, inorganic layers on plastic substrates.

[0062] The layer thickness (determined by scanning electron microscopy) of the inorganic coating is usually between 3 nm and 990 nm, better between 4 nm and 750 nm, ideally between 5 nm and 500 nm.

[0063] The oxygen permeability is reduced by the application of this inorganic layer (measured according to DIN 53380-3 at 23°C and a relative humidity of 50%) compared to the pure paint layer usually by a factor of 2, better by a factor of 5, ideally by a factor of 10 or more.

[0064] The water vapor permeability (measured according to DIN EN ISO 15106-3 at 23°C and a relative humidity of 85%) compared to the pure paint layer is usually reduced by a factor of 2 - 20, better by a factor of 20 - 50, ideally by a factor of 50 - 500 by the application of the inorganic layer.

[0065] In a particularly advantageous embodiment of the invention, the inorganic layer is provided with a further coating of the barrier lacquer.

[0066] The primary task of the transfer film according to the invention is to transfer the combination of barrier lacquer layer and inorganic coating from the carrier film to a target substrate. Target substrates are generally flat materials that cannot easily be coated with inorganic, nanoscale barrier layers. Examples include paper, cardboard, biopolymers (cellophane, polylactic acid, polyhydroxyalkanoates, polybutyl succinates, etc.), (natural) fiber-plastic composites, textiles and nonwovens, as well as conventional plastics with inadequate surface properties for coating using the processes described above, such as PVD.

[0067] To transfer the inorganic layer, hereinafter referred to as metallization, and the lacquer layer, a laminating adhesive (e.g. based on polyurethane) is applied to the target substrate or the inorganic layer.

[0068] This laminating adhesive is characterized by its adhesion to the metallization after drying, which exceeds the bond strength between the coating layer and the carrier film. Typically, the adhesion between the laminating adhesive and the metallization is 2 times higher, preferably 5 times higher, and ideally at least 10 times higher than the bond strength between the barrier coating layer and the carrier film.

[0069] The transfer film is then bonded to the target substrate on the metallized side, as shown schematically in Figure 2.

[0070] To ensure successful transfer of the resist layer and metallization from the carrier to the target substrate, the barrier resist, in addition to the properties mentioned above, is characterized by a higher adhesion between the barrier resist layer and the metallization than the adhesion between the barrier resist layer and the carrier film. Typically, the adhesion between the barrier resist layer and the metallization is a factor of 2, preferably a factor of 5, and ideally at least a factor of 10 higher than the bond strength between the barrier resist layer and the carrier film. Subsequently, in a final step, for example, when wrapping the film, the carrier film is peeled off, leaving both the resist layer and the metallization on the target substrate (see Figure 3).Surprisingly, it turns out that a transfer of the metallization and the barrier coating layer to the target substrate is possible without significant damage to the nanoscale metallization, even without the use of release agents (e.g. butyl acetate, waxes, paraffins, silicones).

[0071] Surprisingly, it turns out that the barrier properties of the metallization and lacquer layer created on the carrier film are largely retained in the final composite and are thus transferred to the target substrate during the transfer process. This now makes it possible to impart barrier properties to substrates where this was previously technically impossible or economically impractical.

[0072] The oxygen permeability (measured according to DIN 53380-3 at 23°C and a relative humidity of 50%) of the composite after transfer of the metallization and the barrier coating layer to the target substrate and after removal of the carrier film is typically less than 10 cm 3 / (m 2 d bar), better under 5 cm 3 / (m 2 d bar), even better under 5 cm 3 / (m 2 d bar), ideally less than 2 cm 3 / (m 2 d bar), each normalized to a layer thickness of 100 pm.

[0073] The water vapor permeability (measured according to DIN EN ISO 15106-3 at 23°C and a relative humidity of 85%) of the composite after transfer of the metallization and the barrier coating layer to the target substrate and after removal of the carrier film is typically below 10 g / (m 2 d) , better below 2 g / (m 2 d) , ideally below 1 g / (m 2d) , each normalized to a layer thickness of 100 pm.

[0074] Thus, the use of the transfer film according to the invention allows the transfer of a barrier lacquer layer and a nanoscale metallization to a target substrate without any significant loss of the oxygen and water vapor barrier. This enables, for example, the use of substrates that themselves have no or no significant barrier properties as primary packaging for sensitive and highly sensitive foods.

[0075] A further advantage of the transferred combination of metallization and barrier lacquer layer is that the metallization in particular acts as a barrier layer against undesirable substances that are particularly found in plastic and paper recyclates (mineral oil, additives, non-intentionally added substances (NIAS)). The use of the transfer film therefore allows the barrier layer consisting of metallization and barrier lacquer layer to be transferred to target substrates containing recycled material and used, for example, in (food) packaging. This approach can also be supplemented with further layers (e.g. ethylene-vinyl acetate lacquers or ethylene-acrylic acid lacquers) so that the target substrate can be thermally joined using thermal sealing. In this way, the target substrate can be provided with barrier properties and can be processed into shaped bodies using a simple lamination process.Application example: Transfer to fiber-based substrate.

[0076] In the decorative finishing sector, finishing foils for transfer metallization are commonplace. This type of finishing foil is used to enhance printed text and, for example, line drawings. This achieves effects similar to, for example, gloss embossing. However, the focus in these applications is on the visual appearance. A commercially available finishing foil from Bergmann Handels OHG

[0077] ( "Creativ-Papier" - finishing foil silver gloss ) has no barrier properties, as shown in Table 1:

[0078] Table 1 : Barrier properties of a standard

[0079] Finishing film

[0080] In the following, it is described how a fiber-based substrate was provided with excellent barrier properties by using the proposed method.

[0081] A 50 μm biaxially oriented PET film (type Mitsubishi Hostaphan RNK 75) was coated with a polyvinyl alcohol-based lacquer in a roll-to-roll process. Surface pretreatment of the film, as is usual in film finishing processes, was deliberately omitted. The lacquer is a water-based, modified PVOH system (Kuraray Exceval AQ 4104) with an ethylene content of 8 mol%. This 8% corresponds in this case to the hydrophobic portion. The PVOH solution was adjusted to a solids content of 15% (w / w). The PET sheet was dried using a convective sheet dryer at a drying temperature of 95 °C. A dry layer weight of approximately 2 g / m 2 reached .

[0082] The coated PET substrate was then vapor-deposited with aluminum on the PVOH side. The vapor deposition was applied using a PVD process under vacuum. The vacuum strength was between 10~ 5 up to 10~ 3 mbar. In this case, the aluminum was evaporated using an electron beam source. The layer thickness of the aluminum vapor deposition was monitored using a quartz crystal and was between 50 and 100 nm. After opening the chamber, the film was reconditioned for 1 day at 23 °C and 50% RH. Reconditioning is the last step in the production of the transfer film. This results in a final structure as described in connection with Figure 1.

[0083] The transfer film is characterized by excellent barrier properties, which are summarized in Table 2.

[0084] Table 2 : Permeation properties of the transfer film,

[0085] Testing was carried out by DAAkS-accredited testing laboratory

[0086] To equip a fiber-based material with

[0087] To ensure barrier properties, the first step was to coat the uncoated side of the fiber-based material (Pack Pro 7.0 packaging paper from Brigl & Bergmeister) with a two-component polyurethane adhesive solution. The ethyl acetate-based solution had a solids content of 65%. Initial drying was carried out using a convective web dryer at a drying temperature of 50°C. In the laminating unit, the adhesive-coated side of the packaging paper was then laminated to the metallized side of the transfer film and wound up.

[0088] The dry film thickness of the adhesive was in a dry film range between 3 g / m 2 and 5 g / m 2 The overall structure at this stage corresponds to that shown in Figure 2 .

[0089] The entire composite was then separated using a rewinding station. Due to the low adhesion forces between the PET film and the PVOH layer, the composite primarily separates at this point. Using this principle, the PVOH + metallization barrier system was transferred from the transfer film to the target substrate. The result was a composite structure as shown in Figure 3, which exhibited the permeation values ​​shown in Table 3.

[0090] Table 3 : Permeation properties of the refined

[0091] Paper, examination was carried out by DAAkS-accredited

[0092] Testing laboratory

Claims

Claims: Composite film for transferring a barrier layer onto another substrate, comprising a carrier film on which a layer sequence of at least one coating layer of a barrier coating and an inorganic layer on the coating layer is applied, wherein the adhesive forces between the coating layer and the carrier film are lower than the adhesive forces between the coating layer and the inorganic layer, characterized in that the barrier coating has a polymer matrix with a hydrophilic and a hydrophobic component, of which the hydrophobic component is between 0.2 and 20% and the hydrophilic component is at least 70%, in each case based on the amount of substance in mol. Composite film according to claim 1, characterized in that the hydrophobic component in the polymer matrix of the barrier coating is between 0.5 and 15 mol%, preferably between 0.5 and 10 mol%.Composite film according to claim 1 or 2, characterized in that the hydrophilic component in the polymer matrix of the barrier coating is selected such that the oxygen permeability of the coating layer, measured according to DIN 53380-3 at 23°C and a relative humidity of 50%, normalized to a layer thickness of 100 pm, is less than 5 cm. 3 / (m 2 d bar). Composite film according to claim 3, characterized in that the hydrophilic component in the polymer matrix is ​​selected such that the oxygen permeability of the coating layer, measured according to DIN 53380-3 at 23°C and a relative humidity of 50%, normalized to a layer thickness of 100 pm, is less than 2.5 cm. 3 / (m 2 d bar), preferably less than 0.5 cm 3 / (m 2 d bar), especially preferably below 0.05 cm 3 / (m 2d bar). Composite film according to one of claims 1 to 4, characterized in that the hydrophobic component in the polymer matrix is ​​selected such that the water vapor permeability of the coating layer, measured according to DIN EN ISO 15106-3 at 23°C and a relative humidity of 85%, normalized to a layer thickness of 100 pm, is still above 10 g / (m²). 2 d) and below 100 g / (m³) 2 d) is . Composite film according to claim 5, characterized in that the hydrophobic component in the polymer matrix is ​​selected such that the water vapor permeability of the coating layer, measured according to DIN EN ISO 15106-3 at 23°C and a relative humidity of 85%, normalized to a layer thickness of 100 pm, is still above 10 g / (m²). 2 d) and below 50 g / (m³) 2 d) , preferably even more than 10 g / (m³) 2 d) and below 20 g / (m³) 2 d) is. Composite film according to one of claims 1 to 6, characterized in that, that the lacquer layer has a thickness between 5 nm and 100 pm, preferably between 7 nm and 50 pm. Composite film according to any one of claims 1 to 6, characterized in that the lacquer layer has a thickness between 10 nm and 30 pm, preferably between 10 nm and 10 pm. Composite film according to any one of claims 1 to 8, characterized in that the inorganic layer has a thickness between 3 nm and 990 nm, preferably between 4 nm and 750 nm, particularly preferably between 5 nm and 500 nm. Composite film according to any one of claims 1 to 9, characterized in that the barrier lacquer is formed from hydrophobically modified PVOH, EVOH, modified EVOH, medium-chain polyhydroxyalkanoates (mPHA), oligomeric lactic acid (oLA), cutin or its derivatives, or from a combination of several of these substances.Composite film according to any one of claims 1 to 10, characterized in that the inorganic layer consists of aluminum (Al), aluminum oxide (AlOx), silicon (Si), silicon oxide (SiOx), or a combination of several of these materials. Composite film according to any one of claims 1 to 11, characterized in that the layer sequence consists of the lacquer layer and the... The inorganic layer on the composite film has a water vapor permeability, measured according to DIN EN ISO 15106-3 at 23 °C and a relative humidity of 85%, normalized to a layer thickness of 100 pm. < / = 1 g / (m 2 d) exhibits a method for transferring a barrier layer to another substrate, wherein - a composite film according to one or more of the preceding patent claims is provided, - the composite film on the side of the inorganic layer is bonded to a surface of the substrate via an adhesive layer, the adhesive for the adhesive layer being selected such that the adhesion of the inorganic layer to the surface of the substrate is greater than that between the lacquer layer and the carrier film, and - the carrier film is then removed, so that the layer sequence consisting of the lacquer layer and the inorganic layer remains on the substrate as a barrier layer. Method according to claim 13, characterized in that the adhesive layer is applied to the surface of the substrate before the composite film is bonded to the surface of the substrate.

Images