Film for sealing a surfacce

Abstract

The invention relates to a film for sealing a surface, preferably a wood surface or a natural fiber surface, more preferably a surface of a veneer, the film comprising a first layer and a second layer, wherein: the second layer has a melting range having a starting point of greater than 80°C, preferably greater than 90°C, more preferably greater than 95°C, most preferably greater than 100°C and having an end point of less than 170°C, preferably less than 160°C, more preferably less than 155°C, most preferably less than 150°C, the end point being a higher temperature than the starting point; the first layer has a melting range having a starting point which is at least 10°C, preferably at least 15°C, most preferably at least 20°C, above the end point of the melting range of the second layer; the first layer and the second layer are integrally bonded to one another.

Description

[0001] PPONTOOIWO / 10.12.2025 1

[0002] Foil for sealing a surface

[0003] The present invention relates to a film for sealing a surface, a semi-finished product comprising such a film, the use of such a film for sealing a surface against liquids at a temperature of at least 80 °C, the use of such a film or such a semi-finished product for the manufacture of a disposable product, a regularly replaceable product or a durable product, a method for manufacturing a multi-layered film, and a sealed product.

[0004] Wooden panels, including those with veneer on the visible side, are usually made water-resistant with a varnish. Tabletops or furniture fronts can be coated with water-based or solvent-based varnishes. These varnishes can also be biodegradable. If the wood, especially in the form of veneer, is very thin, applying varnishes, particularly water-based ones, can lead to undesirable waviness in the veneer. Another disadvantage is that the solvent must evaporate during the varnishing process, or, in the case of a reactive varnish, the curing time must be observed.

[0005] These disadvantages can be circumvented through extrusion coating. For example, paper webs are made hydrophobic with a plastic layer, and cups for vending machines are produced from this coated paper. The plastic layer can also be biodegradable. This process requires that the substrate to be coated is available as roll stock. This is generally not the case with veneers and other wood products. Therefore, this is not a viable manufacturing method if a veneer or other substrate with a wood or natural fiber surface is to be coated. PPONTOOIWO / 10.12.2025 2

[0006] Veneers can be sealed with a film applied via a lamination or pressing process. An example of a biodegradable film is described in US 2008 / 0241509 Al (CHUN-CHIH LAI, October 2, 2008). When multiple veneer layers are used in a composite, sealing is often achieved with an intermediate layer (for example, in JP 2000 / 052306 A, MIKI RIKEN KOGYO KK, February 22, 2000). In these cases, the surface of the top veneer preferably remains uncoated.

[0007] Sealing veneers with a biodegradable multilayer film is also described in the prior art. WO 2020 / 084198 Al (METSALITTO OSUUSKUNTA, April 30, 2020) describes a two-layer film consisting of a polycaprolactone layer and a polycaprolactone-containing layer with a higher melting point. A disadvantage of this solution is its low heat resistance and the resulting lack of hot water resistance, which precludes its use in connection with hot food and beverages or in hot environments (kitchens, conservatories, automobiles).

[0008] Providing a film that adheres well to a surface, but also seals well, especially against hot water, and ideally is also biodegradable, presents a particular challenge.

[0009] It is therefore an object of the present invention to overcome at least some, if not all, of the disadvantages of the prior art products and methods. In particular, it is an object of the invention to provide a film for sealing a surface, preferably a wooden surface or a natural fiber surface, with improved sealing properties, especially improved hot water sealing properties, against liquids. Good adhesion to the surface to be sealed should also be ensured. Furthermore, it is a particular object of the invention to provide such a film which consists of or comprises biodegradable raw materials, so that the film itself is preferably biodegradable.

[0010] The problem is solved by a film, a semi-finished product, a method for producing a film, the use of the film or the semi-finished product, and a sealed product, each according to the independent claims. Advantageous embodiments and further developments are the subject of the dependent claims.

[0011] A first aspect of the invention relates to a film for sealing a surface, preferably a wood surface or a natural fiber surface, more preferably a veneer surface. The film comprises a first layer and a second layer. The second layer has a melting range with a starting point greater than 80 °C, preferably greater than 90 °C, more preferably greater than 95 °C, and most preferably greater than 100 °C; and with an end point less than 170 °C, preferably less than 160 °C, more preferably less than 155 °C, and most preferably less than 150 °C. The end point is a higher temperature than the starting point. The first layer has a melting range with a starting point that is at least 10 °C, preferably at least 15 °C, and most preferably at least 20 °C above the end point of the melting range of the second layer.The first and second layers are bonded together in a materially coherent manner. PPONTOOIWO / 10.12.2025 4.

[0012] In this context, the melting point or melting range of the main melting peak (in DSC) of the main component of the second layer, which serves as the adhesive layer, is relevant. This ensures a suitable viscosity reduction through melting, thus enabling bonding.

[0013] For the first layer, which serves as the top layer, the melting point or melting interval of the main melting peak (in DSC) of the higher-melting component(s) of this layer is relevant. This ensures the structural integrity of the layer during bonding.

[0014] Surface sealing is the process of applying a protective layer (in this case, the film according to the invention) to a surface to prevent the penetration of liquids, particularly at elevated temperatures, or other unwanted substances. The term is described in more detail below.

[0015] A wood surface refers to the outermost layer of an object that consists entirely or partially, preferably predominantly, of wood. This layer is characterized by the natural structure and grain of the wood. A veneer is a thin layer of wood that is applied, for example, to a substrate such as particleboard or MDF for finishing surfaces; or that is used for the manufacture of food containers. A natural fiber surface describes the outermost layer of an object that consists entirely or partially, preferably predominantly, of natural (plant or animal) fibers, such as jute, hemp, or coconut fibers. This surface exhibits the typical texture and structure of the fibers used. PPONTOOIWO / 10.12.2025 5

[0016] Wood and natural fibers include, for example, bamboo fibers, cork, bark, jute fibers, wood fibers, wood chips in the form of fiber mats, fiber mats, fiber woven fabrics, fiber tapes, particleboard, MDF boards (MDF = medium-density fiberboard), OSB boards (OSB = oriented strand board), plywood boards, and laminated wood panels. These materials contain binders that are preferably biodegradable.

[0017] According to generally accepted technical knowledge, a materially bonded connection is a bond formed between layers by atomic or molecular forces. A materially bonded connection is preferably an insoluble bond.

[0018] The film according to the invention can comprise one or more further layers (for example, layers as an aroma barrier, adhesion promoter layers, and / or color layers). The first and second layers can each occur multiple times in the film. The terms 'first' layer and 'second' layer say nothing about how the film is manufactured or how the layers are arranged relative to each other. The possibly present further layer(s) can, for example, be arranged between the first and second layers.

[0019] Preferably, the starting point of the melting interval of the second layer is greater than 100 °C and the end point of the melting interval of the second layer is less than 150 °C.

[0020] Preferably, the endpoint of the melting range of the first layer is less than 90 °C higher, more preferably less than 75 °C higher, more preferably less than 60 °C higher, even more preferably less than 45 °C higher, and most preferably less than 30 °C higher than the starting point of the melting range of the first layer. PPONTOOIWO / 10.12.2025 6

[0021] The melting interval is determined by differential scanning calorimetry (DSC) according to DIN EN ISO 11357-1:2023 and DIN EN ISO 11357-3:2018, where the starting point describes the temperature at the beginning of the melting of the material and the end point describes the temperature when the material has completely melted.

[0022] The first layer, with the higher melting point, serves as a top layer and / or protective layer of the film and seals the surface. It is designed to withstand mechanical, chemical, and thermal influences to ensure the film's sealing function. The second layer acts as an adhesive layer to bond the film to the surface to be sealed. The surface to be sealed is not part of the film according to the invention. When the film according to the invention is applied to the surface, the second layer (adhesive layer) is melted at a temperature below the melting point of the first layer (top layer). This allows the film to adhere well to the surface without the top layer losing its properties, particularly its sealing properties. In particular, the formation of pinholes should be prevented during application to ensure the top layer remains liquid-tight.

[0023] The film according to the invention provides a film suitable for sealing surfaces against warm and hot (80 °C to 100 °C) liquids and foodstuffs containing at least one liquid component. It has surprisingly been found that the film according to the invention achieves good adhesion to surfaces, preferably wooden or natural fiber surfaces, without impairing its sealing properties, particularly its hot water sealing properties. A person skilled in the art would have expected that the first layer would be damaged during the thermal application of the film to a surface, and that, for example, pinholes would form, rendering the film leaky to liquids. This was assumed because the melting intervals of the two layers are very close and relatively high.The closely spaced melting points also allow the film to be produced, particularly through coextrusion, at lower temperatures and therefore with less energy consumption. Furthermore, closely spaced melting points during film production, especially through coextrusion, result in uniform flow behavior, good layer adhesion, and process stability. It is also surprising that good adhesion to surfaces, especially wood and natural fiber surfaces, can be achieved despite high melting points, particularly of the second layer. This is because films with the lowest possible melting points are typically used when optimal adhesion is desired.

[0024] The film according to the invention represents an improvement over the prior art (for example, WO 2020 / 084198 A2, METSA-LITTO OSUUSKUNTA, 30 April 2020) because, among other things, it is heat-resistant and suitable for use with warm and hot foods containing a liquid component. Containers for hot food and beverages can thus be manufactured using the film according to the invention. An advantage over WO 03 / 020803 A2 (APACK AKTIENGESELLSCHAFT FÜR BIOLOGISCHE VERPACKUNGEN, 13 March 2003) is that the film according to the invention can be applied to wood and natural fiber surfaces with good adhesion, and not only to a starch-based substrate. PPONT O OIWO / 10.12.2025 8

[0025] Besides its liquid-tightness, especially at high temperatures, the lamination improves the handling of the surface to be sealed, preferably the surface of a veneer. With a thin substrate, such as a veneer, flexibility is improved and the tendency to splinter is reduced.

[0026] In a preferred embodiment of the first aspect of the invention, the first layer has a melting interval with a starting point that is at most 50 °C, preferably at most 40 °C, most preferably at most 35 °C above the end point of the melting interval of the second layer.

[0027] In another preferred embodiment of the first aspect of the invention, the basis weight of the second layer is 15 - 50 g / m². 2 , preferably 20 - 35 g / m² 2 , most preferred 25 - 30 g / m² 2 The basis weight of the first layer is 20–50 g / m².2 , preferably 25 - 40 g / m² 2 , most preferred 30 - 38 g / m² 2 .

[0028] Films with the specified basis weights have proven particularly advantageous. In particular, these basis weights ensure good surface sealing, especially against aqueous liquids with a temperature in the range of 80–100 °C. Simultaneously, flexibility is improved and the tendency to splinter is reduced. The specified basis weights can result in layer thicknesses of 20 µm to 30 µm for the second layer and 25 µm to 30 µm for the first layer. Lower basis weights can be detrimental to the sealing properties, especially the hot water sealing properties, as well as to the adhesion of the film. Excessively high basis weights can be detrimental to biodegradability. PPONT O OIWO / 10.12.2025 9

[0029] In a further preferred embodiment of the first aspect of the invention, the second layer comprises polybutylene succinate. Preferably, the second layer consists of polybutylene succinate.

[0030] The first layer comprises a polyhydroxyalkanoate and poly(butylene adipate co-terephthalate). Preferably, the first layer consists of a polyhydroxyalkanoate and poly(butylene adipate co-terephthalate). The choice of these polymers results in layers with closely spaced melting intervals, thus providing the advantages mentioned above.

[0031] In this preferred embodiment according to the first aspect of the invention, the second layer can consist of 100% w / w polybutylene succinate. The first layer can consist of 26% w / w polyhydroxyalkanoate and 74% w / w poly(butylene adipate co-terephthalate). The weight fraction of polybutylene succinate, based on the total weight of the second layer, is particularly advantageous for its watertightness, preferably hot watertightness, and for its adhesion to a surface, especially a veneer.

[0032] In this preferred embodiment according to the first aspect of the invention, the basis weight of the second layer can be 25 g / m². 2 and the basis weight of the first layer is 38 g / m² 2 These areal weights result in good density, especially hot water density, while ensuring good biodegradability and good adhesion.

[0033] In a further preferred embodiment of the first aspect of the invention, the second layer comprises poly(butylene adipate co-terephthalate) and a lubricant. Preferably, the second layer consists of poly(butylene adipate co-terephthalate) and a lubricant. The first layer comprises a polyhydroxyalkanoate and poly(butylene adipate co-terephthalate). Preferably, the first layer comprises PPONT O OIWO / 10 . 12 . 2025 10

[0034] A layer of a polyhydroxyalkanoate and poly(butylene adipate co-terephthalate). The choice of these polymers results in layers with closely spaced melting intervals, thus providing the advantages mentioned above.

[0035] In this preferred embodiment according to the first aspect of the invention, the second layer can consist of 99.5% w / w of poly(butylene adipate co-terephthalate) and 0.5% w / w of the lubricant. The first layer can consist of 26% w / w of a polyhydroxyalkanoate and 74% w / w of poly(butylene adipate co-terephthalate). The weight fraction of poly(butylene adipate co-terephthalate), based on the total weight of the second layer, is particularly advantageous for sealing, preferably hot water tightness.

[0036] In this preferred embodiment according to the first aspect of the invention, the basis weight of the second layer can be 25 g / m². 2 and the basis weight of the first layer is 35 g / m² 2 These areal weights result in good density, especially hot water density, while ensuring good biodegradability.

[0037] In a further preferred embodiment of the first aspect of the invention, the second layer comprises poly(butylene adipate co-terephthalate) and a thermoplastic polyester polyurethane. Preferably, the second layer consists of poly(butylene adipate co-terephthalate) and a thermoplastic polyester polyurethane. The first layer comprises a polylactide and polycaprolactone. Preferably, the first layer consists of a polylactide and polycaprolactone. The choice of these polymers results in layers with closely spaced melting intervals, thereby providing the advantages mentioned above. PPONT O OIWO / 10.12.2025 11

[0038] In this preferred embodiment according to the first aspect of the invention, the second layer can consist of 70% w / w of poly(butylene adipate co-terephthalate) and 30% w / w of a thermoplastic polyester polyurethane. The first layer can consist of 80% w / w of a polylactide and 20% w / w of polycaprolactone. The weight fraction of poly(butylene adipate co-terephthalate), based on the total weight of the second layer, is particularly advantageous for the tightness, preferably hot water tightness.

[0039] In this preferred embodiment according to the first aspect of the invention, the basis weight of the second layer can be 30 g / m². 2 and the basis weight of the first layer is 30 g / m² 2 These areal weights result in good density, especially hot water density, while ensuring good biodegradability.

[0040] In a further preferred embodiment of the first aspect of the invention, the second layer comprises poly(butylene adipate co-terephthalate) and a polylactide grafted with maleic anhydride. Preferably, the second layer consists of poly(butylene adipate co-terephthalate) and a polylactide grafted with maleic anhydride. The first layer comprises a polylactide and polycaprolactone. Preferably, the first layer consists of a polylactide and polycaprolactone. The choice of these polymers results in layers with closely spaced melting intervals, thereby providing the advantages mentioned above.

[0041] In this preferred embodiment according to the first aspect of the invention, the second layer can consist of 80% w / w of poly(butylene adipate co-terephthalate) and 20% w / w of a polylactide grafted with maleic anhydride. The first layer can consist of 80% w / w of a polylactide and 20% w / w of polycaprolactone. The weight fraction of poly(butylene adipate co-terephthalate), based on the total weight of the second layer, is particularly advantageous for the tightness, preferably hot water tightness.

[0042] In this preferred embodiment according to the first aspect of the invention, the basis weight of the second layer can be 30 g / m². 2 and the basis weight of the first layer is 30 g / m² 2 These areal weights result in good density, especially hot water density, while ensuring good biodegradability.

[0043] In a preferred embodiment of the first aspect of the invention, the first layer comprises at least one first polyester. Preferably, the first polyester is selected from the group consisting of: polyhydroxyalkanoates (PHA), polylactides (PLA), poly(butylene succinate co-adipate) (PBSA), poly(butylene succinate co-terephthalate) (PBST), polyglycolic acid (PGA), polyesteramides, poly(sebacic acid), and copolymers thereof. More preferably, the first polyester is selected from the group consisting of polyhydroxyalkanoates (PHA) and polylactides (PLA) and copolymers thereof. The second layer comprises at least one second polyester. Preferably, the second polyester is selected from the group consisting of: polybutylene succinate (PBS) and

[0044] Poly(butylene adipate co-terephthalate) (PBAT). The second polyester can be present in a mass fraction of at least 60% w / w, preferably at least 70% w / w, particularly preferably at least 80% w / w, based on the total weight of the second layer.

[0045] Within the scope of the present invention, polyesters also include copolymers. Copolyesters are polymers produced by the reaction of two or more different acid and / or alcohol components. The phrase 'and copolymers thereof' means that the respective polyester includes not only the specified polyester types themselves, but also copolymers of these. PPONT O OIWO / 10 . 12 . 2025 13

[0046] Polyester types can include those produced by incorporating different monomers.

[0047] If the first polyester is a polyhydroxyalkanoate, the first polyester is preferably present in a mass fraction of at least 20% w / w, preferably from 20% w / w to 80% w / w, more preferably from 20% w / w to 50% w / w, most preferably from 20% w / w to 30% w / w, based on the total weight of the first layer.

[0048] If the first polyester is a polylactide, the first polyester is preferably present in a mass fraction of at least 50% w / w, preferably at least 60% w / w, more preferably at least 70% w / w, most preferably at least 80% w / w, based on the total weight of the first layer.

[0049] Polyhydroxyalkanoates (PHAs) are biodegradable polyesters synthesized by the microbial fermentation of sugars or lipids. They consist of hydroxy fatty acid monomers. Polylactides (PLAs; CAS numbers: 26100-51-6 (polylactic acid), 26680-10-4 (polylactide)) are thermoplastic polyesters produced by the polymerization of lactic acid monomers (2-hydroxypropanoic acid). Poly(butylene succinate co-adipate) (PBSA) is a copolyester produced by the copolymerization of butylene succinate and butylene adipate. Poly(butylene succinate co-terephthalate) (PBST) is a copolyester containing butylene succinate and terephthalic acid as monomers. Polyglycolic acid (PGA; CAS number: 26009-03-0) is an aliphatic polyester produced by the polymerization of glycolic acid. Polyesteramides (PEA) are copolymers containing ester and amide groups in their polymer structure.Poly(sebacic acid) is an aliphatic polyester produced by the polymerization of sebacic acid monomers. PPONTOOIWO / 10.12.2025 14.

[0050] Polybutylene succinate (PBS; CAS number: 25777-14-4) is an aliphatic polyester produced by the condensation reaction of succinic acid and 1,4-butanediol. It is characterized by good thermoplastic processability and biodegradability. Poly(butylene adipate co-terephthalate) (PBAT) is a copolyester synthesized from butylene adipate and terephthalic acid.

[0051] Preferably, the second layer does not include polycaprolactone (PCL; CAS number: 24980-41-4).

[0052] The film, preferably the first and / or second layer, may further comprise thermoplastic, biodegradable polymers, preferably selected from the group consisting of: thermoplastic polyester polyurethanes, polyamides, polyvinyl alcohols, polyorthoesters, polydioxanones, thermoplastic starch, derivatized starch, collagen, chitosan, cellulose, cellulose esters, cellophane, alginates, casein and pectin.

[0053] The layers of the film may comprise further additives. For example, the film, preferably the first and / or second layer, may comprise inorganic fillers, preferably selected from the group consisting of: chalk, talc, silica, kaolin, mica, metal oxides, carbon black, and metal hydroxides. For example, the film, preferably the first and / or second layer, may also comprise processing aids, preferably selected from the group consisting of: lubricants, antiblocking agents, stabilizers, dyes, antioxidants, metal deactivators, and processing aids.

[0054] It has been shown that a film with a polyester in both the first and second layers, particularly with the polyesters listed in PPONTOOIWO / 10.12.2025 15, is especially dense, and particularly hot-water resistant, when the weight fraction of the second polyester is within the specified range. Furthermore, such a film exhibits particularly good adhesion to surfaces, especially wood and natural fiber surfaces. In addition, the polyesters mentioned are biodegradable.

[0055] In another preferred embodiment of the first aspect of the invention, the first polyester is a polyhydroxyalkanoate and the second polyester is polybutylene succinate. Alternatively, the first polyester is a polyhydroxyalkanoate and the second polyester is poly(butylene adipate co-terephthalate). Alternatively, the first polyester is a polylactide and the second polyester is poly(butylene adipate co-terephthalate).

[0056] Within the context of the present invention, the term "or" is to be understood as an exclusive disjunction. "A or B" states that exactly one of the two statements is true (if the disjunction is true).

[0057] It was found that a film with the described polyester combinations exhibits particularly good sealing properties for the first and second polyesters, preferably hot water resistance. Furthermore, the aforementioned advantages regarding surface adhesion also apply here.

[0058] In a further preferred embodiment of the film of the first aspect of the invention, the polyhydroxyalkanoate is selected from the group consisting of polyhydroxybutyrate (PHB; CAS number: 26744-04-7), polyhydroxyvalerate (PHV; CAS number: 83120-66-5), polyhydroxybutyrate-co-valerate (PHBV; CAS number: 80181-31-3) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH; CAS number: 147398-31-0). PPONT O OIWO / 10.12.2025 16

[0059] For example, the product Nodax from Danimer Scientific contains the polymer Poly ( 3-hydroxybutyrate-co-3-hydroxyhexanoate ).

[0060] The presence of a first polyhydroxyalkanoate of this group does not preclude the presence of another polyhydroxyalkanoate in the first layer.

[0061] The aforementioned polyhydroxyalkanoates are particularly well suited for the production of a film according to the invention.

[0062] In a further preferred embodiment of the first aspect, the first layer comprises at least one further polymer selected from the group consisting of: poly(butylene adipate co-terephthalate) (PBAT) and polycaprolactone (PCL). Additionally or alternatively, the second layer comprises at least one further polymer selected from the group consisting of: thermoplastic polyester polyurethanes (PES-TPU) and polylactides (PLA).

[0063] Polycaprolactone (PCL; CAS number: 24980-41-4) is an aliphatic polyester produced by the ring-opening polymerization of s-caprolactone. Thermoplastic polyester polyurethanes (PES-TPU) are polymers formed from a reaction between polyester polyols and isocyanates.

[0064] Preferably, the polylactide of the second layer is grafted with maleic anhydride. This means that the polymer chains of the polylactide have been chemically modified with maleic anhydride by introducing functional groups into the structure, for example to improve compatibility and adhesion with other materials and to increase the reactivity of the surface. PPONTOOIWO / 10.12.2025 17

[0065] In another preferred embodiment of the first aspect, the first polyester is a biodegradable polyester and / or the second polyester is a biodegradable polyester.

[0066] Within the scope of the present invention, a polyester is biodegradable if it is industrially compostable according to DIN EN 13432:2000-12, preferably if it is home compostable according to DIN EN 17427:2022-08.

[0067] In another preferred embodiment of the first aspect, the film consists of at least 90%, preferably at least 95%, more preferably at least 98%, and most preferably 100% biodegradable materials.

[0068] Preferably, the film according to the invention has at least the same biodegradability as the material of the surface to which it is applied. Even more preferably, the film is industrially compostable according to DIN EN 13432:2000-12, and even more preferably, it is home compostable according to DIN EN 17427:2022-08.

[0069] The inventors have found that it is a particular challenge to provide a film with the properties described above (for example, impermeability, preferably hot water impermeability, and adhesion to the surface) that is also biodegradable. Despite this limitation, biodegradable films with the characteristics described herein have been found that meet all these requirements. Thus, the entire composite can be composted. This is in contrast to coatings and paints designed for a long service life or where biodegradability has not been taken into account. PPONT O OIWO / 10.12.2025 18

[0070] In another preferred embodiment of the first aspect, the film has a total thickness of 10 pm to 300 pm, preferably of 30 pm to 200 pm, and even more preferably of 40 pm to 100 pm.

[0071] In another preferred embodiment of the first aspect, the second layer has a thickness of 5 pm to 200 pm, preferably of 15 pm to 100 pm, and more preferably of 20 pm to 50 pm.

[0072] In another preferred embodiment, the coating is applied to a surface, preferably a wooden surface or a natural fiber surface, more preferably a veneer surface, at a temperature of 120°C to 130°C and a pressure of 8.4 N / cm². 2 A hot water tightness test was performed on a pressed film for 60 seconds. The hot water tightness is characterized by the fact that no water penetrates the surface after the film has been exposed to a 3 cm high column of water for 5 minutes, with the water temperature being approximately 100 °C at the beginning of this period and remaining in the range of 70 °C to 100 °C during this period.

[0073] Preferably, the condition that no water penetrates the surface is met if no water penetration is visible during a test with the naked eye. Preferably, the hot water tightness is further characterized by the absence of any of the following phenomena on the surface and on the film, selected from the group consisting of: water stains, swelling, holes, cracks, spalling, and waviness. The surface and the film are to be examined where the composite was exposed to the water column. PPONT O OIWO / 10.12.2025 19

[0074] The test is passed if no water penetrates the veneer, no water leaks or swelling are observed, no holes or cracks appear in the coating, and no foil peels from the veneer. The test is failed if visible water leaks occur, swelling appears, cracks or holes appear in the coating, the coating peels off, or the veneer becomes wavy.

[0075] Peeling of the foil indicates insufficient adhesion between the foil and the veneer at elevated temperatures. Holes and cracks occur during lamination if the top layer is not sufficiently temperature-resistant under the process parameters required to activate the adhesive layer. Water absorption in the veneer leads to swelling and consequently to waviness in the test area. Visible water stains indicate high water absorption.

[0076] Such hot water tightness makes it possible to manufacture containers (for example, cups) which are suitable for filling with liquids, especially hot liquids.

[0077] In another preferred embodiment of the first aspect, the veneer is treated at a temperature of 120°C to 130°C and a pressure of 8.4 N / cm². 2 During 60 s, the pressed-on film exhibits a peel resistance of at least 0.5 N / mm, preferably at least 0.6 N / mm, measured with a 180° peel test according to DIN EN ISO 8510-2:2010-12.

[0078] The film according to the invention exhibits particularly good adhesion to a surface, especially to a wooden or natural fiber surface, due to its peel resistance. PPONTOOIWO / 10.12.2025 20

[0079] Preferably, the film of the first aspect of the invention also exhibits seam strength in hot water. For this purpose, the film is bonded to itself so that the outer layers (first layer) lie against each other. A veneer is pressed onto each of the two outer adhesive layers (second layer). The resulting seam is placed under mechanical tension and immersed in hot water for 5 minutes, with the water temperature starting at approximately 100 °C and remaining between 70 °C and 100 °C during this period. If the bonded seam opens or shows visible partial detachment, the test is considered failed. If the bonded seam remains visually intact, the test is passed. It has been observed that in films that do not meet the requirements for seam strength in hot water, the seam typically opens within seconds of immersion in the hot water.The test for seam strength is described in more detail below.

[0080] A second aspect of the invention relates to a semi-finished product. The semi-finished product comprises a film according to the first aspect of the invention. The semi-finished product also comprises a substrate with a surface, preferably a wood surface or a natural fiber surface. Even more preferably, the substrate is a veneer with a surface. The second layer of the film is the layer facing the substrate and is bonded to the surface of the substrate in a materially inert manner.

[0081] A semi-finished product is a pre-made raw material that is processed into finished products in further manufacturing steps.

[0082] The substrate can be, for example, a veneer. However, it can also be any other workpiece with a surface, preferably a wood or natural fiber surface. PPONTOOIWO / 10.12.2025 21

[0083] The substrate, preferably the veneer, preferably has a thickness of 0.1 mm to 8 mm, more preferably of 0.2 mm to 4 mm, and particularly preferably of 0.3 mm to 2 mm. If the substrate is a veneer, it can be sawn veneer, sliced ​​veneer, or rotary-cut veneer. The veneer is preferably obtained from maple, acacia, aningre, apple, birch, pear, bubinga, beech, ebony, oak, service tree, yew, ash, eucalyptus, spruce, chestnut, pine, cherry, larch, limba, louro, mahogany, makassar, walnut, olive, rosewood, elm, fir, teak, tulipwood, willow, wenge, zebrano, or Swiss pine.

[0084] The substrate can be coated with the film on one or more surfaces. For example, if a veneer is coated with film on both sides, a cup can be manufactured from this semi-finished product, with a seam created by welding the film applied to the inside of the cup and the film applied to the outside. Depending on the intended use, the semi-finished product can also be further processed into a finished product in other ways. Furthermore, several layers of veneer can be bonded together by coating both sides of a veneer. This bonding is achieved by applying energy (for example, using an ultrasonic sonotrode, a high-frequency coil, or thermal activation (IR emitter, hot air, contact heat)). A solvent can also be used for activation.The coating of a veneer allows for essentially splinter-free bending and thus the production of three-dimensional products such as a drinking cup (in contrast to products where a veneer is used only planarly, without bending). PPONT O OIWO / 10.12.2025 22.

[0085] The properties of a materially bonded connection described above also apply to the materially bonded connection between the film and the substrate.

[0086] The preferred embodiments of the first aspect of the invention are also applicable to the second aspect. The advantageous properties (for example, hot water tightness and high peel resistance) of the film of the first aspect of the invention also apply to the semi-finished product of the second aspect of the invention.

[0087] A third aspect of the invention relates to a sealed product. The sealed product comprises a film according to the first aspect of the invention. At least one surface, preferably a wooden surface or a natural fiber surface, of the sealed product is sealed by the film. The sealed product is selected from the group consisting of:

[0088] - Disposable products, preferably selected from the group consisting of disposable plates, disposable cups, disposable cutlery, disposable drinking straws, disposable flower pots and disposable boxes;

[0089] - Products that need to be replaced regularly, preferably selected from the group consisting of cutting boards, trays and surfaces used in exhibition stand construction; and

[0090] - durable products, preferably selected from the group consisting of furniture fronts, appliance coverings, parquet flooring, interior finishing products, insulation underlays and vehicle construction products.

[0091] At least one surface of the sealed product is sealed by the film when the surface is exposed to a temperature of 120°C to 130°C and a pressure of 8.4 N / cm². 2 during 60 s on pressed foil exhibits a tightness, the tightness being characterized by the fact that no PPONT O OIWO / 10. 12. 2025 23

[0092] Water penetrates the surface after the film has been exposed to a 3 cm high column of water at 25 °C for 5 minutes.

[0093] Preferably, at least one surface of the sealed product is even hot water-tight. The same conditions apply as for tightness, except that the temperature of the water column is 100°C at the beginning of the period and 70°C to 100°C instead of 25°C during the period.

[0094] Single-use products are designed for a limited number of uses or short-term use before being disposed of. While they can be reused several times (for example, a disposable cup refilled multiple times for drinking), they are generally not intended for long-term use. Regularly replaceable products must be renewed at regular intervals due to wear and tear or use. Durable products are designed for long-term use and are long-lasting. The use of durable products requires that the film does not come into contact with biodegradable microorganisms, or only comes into contact with them occasionally, if the film is biodegradable as described herein.

[0095] The preferred embodiments of the first and second aspects of the invention are also applicable to the third aspect. The advantageous properties (for example, the hot water tightness) of the film of the first aspect of the invention also apply to the sealed product of the third aspect of the invention.

[0096] A fourth aspect of the invention relates to a method for producing a multilayer film, preferably a film according to the first aspect of the invention. The method comprises the following steps: PPONT O OIWO / 10. 12. 2025 24

[0097] - Providing initial raw materials;

[0098] - Providing a second raw material; and

[0099] - Manufacturing the multilayer film.

[0100] The multilayer film is produced by co-extrusion, preferably by blown-core extrusion or slot extrusion, of the first and second raw materials, whereby a first layer is produced from the first raw material and a second layer is produced from the second raw material. Alternatively, the multilayer film is produced by producing a first film from the first raw material, preferably by blown-core extrusion or slot extrusion; producing a second film from the second raw material, preferably by blown-core extrusion or slot extrusion; and laminating the first and second films, whereby a first layer is produced from the first film and a second layer is produced from the second film. It is also possible to bond the two layers directly to a substrate during lamination.

[0101] The second layer has a melting interval with a starting temperature greater than 80°C, preferably greater than 90°C, more preferably greater than 95°C, and most preferably greater than 100°C. The melting interval has an endpoint of less than 170°C, preferably less than 160°C, more preferably less than 155°C, and most preferably less than 150°C, the endpoint being a higher temperature than the starting temperature. The first layer has a melting interval with a starting temperature at least 10°C, preferably at least 15°C, and most preferably at least 20°C above the endpoint of the melting interval of the second layer.

[0102] Layer lies . PPONT O OIWO / 10 . 12 . 2025 25

[0103] In a preferred embodiment of the fourth aspect of the invention, the first layer has a melting interval with a starting point that is at most 50 °C, preferably at most 40 °C, most preferably at most 35 °C above the end point of the melting interval of the second layer. Particularly preferred basis weights and compositions of the first and second layers have already been described above in connection with the film as such and apply analogously within the framework of the manufacturing process.

[0104] The raw materials can be in the form of granules, for example, and may include other components besides the granules.

[0105] This results in a multi-layered film with the advantages already described in relation to the preceding aspects of the invention. The preferred embodiments of the preceding aspects of the invention are also applicable to the fourth aspect.

[0106] Preferably, the first raw material comprises a first polyester, wherein the first polyester is preferably selected from the group consisting of: polyhydroxyalkanoates, polylactides, poly(butylenesuccinate-co-adipate), poly(butylenesuccinate-co-terephthalate), polyglycolic acid, polyesteramides, poly(sebacic acid) and copolymers thereof; more preferably selected from the group consisting of polyhydroxyalkanoates and polylactides.

[0107] Preferably, the second raw material comprises a second polyester, wherein the second polyester is preferably selected from the group consisting of: polybutylene succinate and poly(butylene adipate co-terephthalate) and copolymers thereof. The second polyester is present in a mass fraction of at least 60% w / w, preferably at least 70% w / w, and particularly preferably at least 80% w / w.

[0108] % w / w before, based on the total weight of the second raw material.

[0109] A fifth aspect of the invention relates to a method for producing a semi-finished product, preferably a semi-finished product according to the second aspect of the invention. The method comprises the following steps:

[0110] - Producing a multilayer film using a method according to the fourth aspect of the invention; or providing a film according to the first aspect of the invention;

[0111] - Providing a substrate with a surface, preferably a wooden surface or a natural fiber surface, more preferably the substrate is a veneer with a surface; and

[0112] - Connecting the substrate to the film.

[0113] The substrate is preferably bonded to the film using a dry lamination system, preferably selected from the group consisting of: roller calender, double belt calender and film laminator. Alternatively, the bonding is carried out using a heated press.

[0114] The second layer is the layer facing the substrate. This second layer is melted and pressed onto the substrate surface under pressure. In its molten (i.e., liquid) state, it penetrates at least partially into the surface. The first layer is not melted (and therefore retains its solid form).

[0115] As described above, multiple surfaces of the substrate can also be coated. For example, with a veneer, both sides can be coated, either in one or two coating passes. PPONTOOIWO / 10.12.2025 27

[0116] The systems for bonding the substrate to the film are familiar to the specialist. A roller calender uses two or more heated rollers to bond the substrate to the film under pressure and heat. A double-belt calender comprises two parallel, heated, endless belts that guide the substrate and film between them and bond them under pressure and heat. A film laminator laminates the film onto a substrate by heating and pressing it. A heated press uses heated press plates to bond the substrate and film.

[0117] The method according to the fifth aspect of the invention enables the production of a semi-finished product with the advantages already described in relation to the preceding aspects. The preferred embodiments are also applicable here.

[0118] A sixth aspect of the invention relates to the use of a film according to the first aspect of the invention for sealing a surface, preferably a wooden surface or a natural fiber surface, more preferably a veneer surface, against liquids of a temperature of at least 80 °C, preferably at least 90 °C, particularly preferably at least 100 °C.

[0119] Preferably the temperature of the liquids is at most 105 °C, preferably at most 100 °C, even more preferably at most 95 °C, most preferably at most 85 °C.

[0120] The same requirements for tightness, preferably hot water tightness, apply here as described above. The surface can, for example, be part of a product described above. The liquids are preferably aqueous liquids. Preferably, the liquid is a component of a foodstuff with at least one liquid component, wherein, within the scope of the present invention, stimulants are considered foodstuffs.

[0121] For example, the film according to the invention can be used to seal the surface(s) of a disposable veneer cup used for filling with a hot beverage. It is surprising that the film of the first aspect of the invention is suitable as a sealing film for such an application. This is because one would have expected that either the adhesion of the second layer (adhesive layer) to the surface, particularly to the wood or natural fiber surface, or the tightness of the top layer (first layer) would be insufficient when used with liquids at elevated temperatures.

[0122] A seventh aspect concerns the use of a film according to the first aspect and / or a semi-finished product according to the second aspect for the manufacture of a disposable product, preferably selected from the group consisting of disposable plates, disposable cups, disposable cutlery, disposable drinking straws, disposable flower pots and disposable boxes; a regularly replaceable product, preferably selected from the group consisting of cutting boards, trays and surfaces in exhibition stand construction; or a durable product, preferably selected from the group consisting of furniture fronts, appliance covers, parquet flooring, interior finishing products, insulation underlays and vehicle construction products.

[0123] The invention will now be described using specific exemplary embodiments. These embodiments are not intended to restrict the core of the invention in any way, but rather to facilitate understanding of the invention. PPONTOOIWO / 10.12.2025 29

[0124] Figure 1: Illustrative representation of a side view of a foil 1 according to the invention;

[0125] Figure 2: Illustrative representation of a semi-finished product 6, comprising a foil 1 according to the invention;

[0126] Figure 3: Test setup with a film 1 and an adhesion test strip 11 on a veneer 3 for performing an adhesion test; 3A: Top view of the coated polyester fabric 13; 3B: Side view of the adhesion test strip 11; 3C: Top view of the adhesion test strip 11; 3D: Top view of the veneer 3; 3E: Side view of the test setup before pressing;

[0127] Figure 4: Test setup with a self-bonded film 1 as seam film 8 and veneers 3 for performing a seam strength test in hot water; 4A: Production of the seam film 8; 4B: Side view of the pressed veneers 3 with the seam film 8; 4C: Top view of the pressed veneers 3; 4D: Top view of the tube 12; 4E: Isometric view of the tube 12;

[0128] Figure 5: Photographs of veneers 3 after the hot water tightness test; and

[0129] Figure 6: Photographs of tubes 12 after the seam strength test.

[0130] Films according to the invention 1 and films not according to the invention were produced by extrusion, co-extrusion, or lamination. Four films according to the invention (examples 1, 2, 4, and 5) and two films not according to the invention (examples 3 and 6) are listed in Table 1. PPONTOOIWO / 10.12.2025 30

[0131] Table 1 Table 1 lists the first polyesters used (PHA: polyhydroxyalkanoate (e); PLA: polylactide (e)), the other components used in the first layer 4 (PBAT: poly(butylene adipate co-terephthalate); PCL: polycaprolactone), the second polyesters used (PBS: polybutylene succinate; GM: lubricant; PBAT; PCL), the other components used in the second layer 5 (PES-TPU: thermoplastic polyester polyurethanes; MAH-g-PLA: maleic anhydride-grafted polylactide), the basis weights of the first layer 4 and the second layer 5, and the manufacturing process (CE: coextrusion; LA: lamination; EX: extrusion) of the resulting multilayer film 1. PPONT O OIWO / 10.12. 2025 31

[0132] In extrusion, especially coextrusion, the temperature profile in the extruders is particularly relevant; in lamination, pressure, temperature, time, and lamination speed play a crucial role. The specialist is aware of how to select the appropriate values ​​for these parameters for the materials being processed. For example, a temperature profile of 160°C in the cylinder, 180°C in the adapter, 155°C in the die, and a melt temperature of 140°C to 160°C may be required, with the melt pressure in the range of 50 bar to 135 bar. The preceding process parameters were used for the coextrusion of the film from Example 1. In the lamination process on a double-belt laminating machine, the following conditions can be set: lamination temperatures of 110°C, 120°C, and 130°C in successive heating zones on the upper and lower belts, and a pressure of 5 N / cm². 2, a laminating speed of 3 m / min and the placement of the films between two layers of silicone paper .

[0133] Furthermore, Table 1 indicates whether the corresponding film 1 is a film 1 according to the invention or not. The layer thickness of the first layer 4 of Example 1 is approximately 30 pm and the layer thickness of the second layer 5 is approximately 20 pm. In all examples, the layer thickness of the first layer 4 is in the range of 25 pm to 30 pm; and the layer thickness of the second layer 5 is in the range of 20 pm to 30 pm. The products listed in Table 2 were used for the production of the films 1 listed in Table 1. PPONTOOIWO / 10.12.2025 32

[0134] Table 2

[0135] The melting ranges of the films 1 described in Table 1 correspond to the melting ranges according to the independent and dependent claims. At least the films 1 from Examples 1, 2, 4 and 5 (films 1 according to the invention) are industrially compostable according to DIN EN 13432:2000-12; and at least the films 1 from Examples 1 and 2 are additionally home compostable according to DIN EN 17427:2022-08. The weight fraction (% w / w) of the second polyester in each case, based on the total weight of the second layer 5 in each case, is within the range according to the independent and dependent claims. This is particularly advantageous for the tightness, preferably hot water tightness.

[0136] Figure 1 shows a side view of a film 1 with a first layer 4 and a second layer 5, which are bonded together. Figure 2 shows a side view of a semi-finished product 6, which comprises a substrate 7 on whose surface 2 a film 1 is bonded together, wherein the second layer 5 (adhesive layer) is the layer facing the surface 2 and the first layer 4 (top layer) is arranged above it.

[0137] The tests described in the following sections were carried out using the foils listed in Table 1. The veneers used for the tests are commercially available maple (thickness = 0.35 mm) or birch (thickness = 0.40 mm) veneers.

[0138] Hot water tightness

[0139] The foils 1 described above are pressed on both sides onto a veneer 3 measuring at least 12 cm x 12 cm using a stamping press. The pressing is carried out on a stamping press at 120 °C or 130 °C and a pressure of 8.4 N / cm². 2 for 60 seconds. A silicone rubber sealing ring is placed on the coated veneer 3. A steel tube with a height of 100 mm and a wall thickness of 4 mm is placed on the sealing ring. Both the sealing ring and the steel tube have an inner diameter of 107 mm. 3 dl of boiling water is poured in and left to stand for 5 minutes. This results in a water column of approximately 3.3 cm. The water is then drained and the veneer surface is inspected. PPONTOOIWO / 10.12.2025 34

[0140] The test is considered passed if no water has penetrated the veneer 3; no water leaks or swelling are observed; no holes or cracks appear in the coating; and no flaking of the foil 1 from the veneer 3 is visible. The test is failed if visible water stains are present, swelling, cracks, or holes appear in the coating, or flaking of the coating occurs, or if waviness of the veneer 3 is visible.

[0141] The hot water tightness test was carried out with veneers 3 made of maple and birch.

[0142] Liability test

[0143] For the adhesion test, an adhesion test strip 11 is required. For this purpose, a non-elastic polyester fabric 13 (PET fabric beige, 23 cm x 30 cm, STA89 / 20A natural, Heinrich Hühn GmbH, Berlin, Germany) was used, covering an area of ​​8 cm x 30 cm with a weight of 120 g / m². 2the adhesive layer to be tested (i.e., the second layer 5 of the film 1 to be tested) coated (press press: 150 °C top and bottom, 50 N / cm²) 2 , 60 s; then: cooling press: 20 s, 20 N / cm² 2 The adhesive layer is applied along one long edge, leaving the rest of the polyester fabric 13 uncovered (Figure 3A). The coated polyester fabric 13 is then cut into 5 cm x 20 cm adhesion test strips 11 (Figures 3B and 3C). The cut edges 15 are shown as dashed lines in Figure 3A for illustrative purposes. The adhesion test strip 11 comprises a coated area of ​​5 cm x 8 cm and an uncoated area of ​​5 cm x 12 cm.

[0144] The foils 1 described above are glued onto a 6 cm x 18 cm veneer 3 (Figure 3D; grain direction 9 along the long edge of the veneer 3) in a stamping press. A 5 cm x 20 cm adhesion test strip 11 is placed on top. The adhesive layer of the adhesion test strip 11, described above, is on the side facing the veneer. A 10 cm long release paper 14 is inserted between the foil 1 and the adhesion test strip 11 at a short end of the veneer to create an unglued section for clamping in the tensile testing machine. The coated surface of the adhesion test strip 11 lies on the foil 1, and the uncoated surface of the adhesion test strip 11 lies on the release paper 14 (Figure 3E). The pressing process takes place on a stamping press at 120 °C or 130 °C, with a pressure of 8.4 N / cm². 2The tensile test was performed for 60 seconds according to DIN EN ISO 8510-2:2010-12 (180° peel test). The adhesion test was performed using maple veneer 3.

[0145] Seam strength in hot water

[0146] To test the seam strength, the foil 1 is first sealed against itself (stamp press: 130 °C top and bottom, 50 N / cm²). 2 , 60 s; then: cooling press: 20 s, 20 N / cm² 2) , so that the top layers (first layers 4) lie on top of each other. This creates a seam foil 8 with the original top layer (first layer 4) on the inside and the adhesive layer (second layer 5) on both outer sides (Figure 4A). This seam foil 8 is cut into 1 cm wide strips. The veneer 3 is cut into 12 cm x 5 cm pieces, with the grain direction 9 of the wood fibers running along the long edge. The strip of seam foil 8 is placed on a short edge of the veneer 3 and covered with a second veneer 3 (also with the short edge facing it) so that, after pressing, a 23 cm x 5 cm piece of veneer 3 with an overlapping seam in the middle is formed (Figures 4B and 40). Pressing is carried out with a pressure of 8.4 N / cm². 2for 60 s at a temperature 15 °C - 20 °C above the melting point of the adhesive layer (second layer 5). The newly created short edges are reinforced with adhesive tape and fixed with staples 10, overlapping by 1 cm. This creates a tube 12 5 cm high, with a circumference of 22 cm, with one glued and one stapled seam (Figures 4D and 4E).

[0147] For the test, the device described in the hot water tightness test (without the coated veneer 3) is filled with boiling water (approx. 100 °C) until the tube 12 is completely submerged when placed inside. Approximately 500 ml of water is required for this. The tube 12 is placed inside and left to stand for 5 minutes. If the glued seam opens or shows visible signs of delamination, the test is considered failed. If the glued seam remains visually intact, the test is passed.

[0148] The seam strength test was performed with veneers 3 made of maple and birch.

[0149] Results

[0150] In the case of the films 1 according to the invention (numbers 1, 2, 4 and 5), no detachment of the film 1 from the veneer 3 occurs during the hot water tightness test, and the veneer 3 remains dry (Table 3). These films 1 have thus passed the test, both with veneers 3 made of maple and birch. In Example 6, a film 1 without a top layer (first layer 4) is used, which only has an adhesive layer (second layer 5) made of PBS. With this embodiment, no detachment of the film is visible, but the veneer is completely wet after the test.

[0151] The use of an adhesive layer alone is therefore insufficient, as it becomes leaky to liquids at the latest when applied to the veneer 3, especially at high temperatures. Therefore, as in the embodiments according to the invention, a top layer with a higher melting point than that of the adhesive layer is required. Figure 5 shows two veneers 3 after the hot water tightness test. In the left veneer 3, water has penetrated the veneer 3, water stains are visible, and the veneer 3 is wavy. The left veneer 3 has therefore failed the test. These phenomena do not occur in the right veneer 3, which passed the test.

[0152] Table 3

[0153] The results of the adhesion test are listed in Table 4.

[0154] All films exhibit a sufficiently high peel resistance, indicating good adhesion to the veneer 3.

[0155] Table 4 PPONTOOIWO / 10.12.2025 38

[0156] In the foil 1 from embodiment 3, the melting zone lies below the inventive zone, and the PCL used is not suitable as an adhesive layer to ensure good seam strength in hot water (Table 5). All other foils 1 are suitable for forming a seam with themselves that remains intact even at elevated temperatures in an aqueous environment. Figure 6 shows a tube 12 on the left that passed the seam strength test. The seam on the right-hand tube 12 has burst. Thus, this tube 12 failed the test.

[0157] Table 5

[0158] The films according to the invention from Examples 1, 2, 4 and 5 meet the requirements for a sealing film, for example when used in a food container with hot, liquid food or drinks.

Claims

PPONTOOIWO / 10.12.2025 39 Patent claims 1. A film (1) for sealing a surface (2), preferably a wood surface or a natural fiber surface, more preferably a surface (2) of a veneer (3), the film (1) comprising a first layer (4) and a second layer (5), wherein - the second layer (5) has a melting interval - with a starting temperature greater than 80 °C, preferably greater than 90 °C, even more preferably greater than 95 °C, most preferably greater than 100 °C; and - with an endpoint of less than 170 °C, preferably less than 160 °C, more preferably less than 155 °C, most preferably less than 150 °C, wherein the endpoint is a higher temperature than the starting point; and - the first layer (4) has a melting interval with a starting point that is at least 10 °C, preferably at least 15 °C, most preferably at least 20 °C above the end point of the melting interval of the second layer; wherein the first layer (4) and the second layer (5) are materially bonded together.

2. A film (1) according to claim 1, wherein the first layer (4) has a melting interval with a starting point that is at most 50 °C, preferably at most 40 °C, most preferably at most 35 °C above the end point of the melting interval of the second layer (5).

3. A film (1) according to one of the preceding claims, wherein the basis weight of the second layer (5) is 15 - 50 g / m² 2 , PPONTOOIWO / 10.12.2025 40 preferably 20 - 35 g / m² 2 , most preferred 25 - 30 g / m² 2 is and wherein the basis weight of the first layer (4) is 20 - 50 g / m² 2, preferably 25 - 40 g / m² 2 , most preferred 30 - 38 g / m² 2 amounts.

4. A film (1) according to any one of claims 1 to 3, wherein the second layer (5) comprises polybutylene succinate, preferably consisting of polybutylene succinate, and wherein the first layer (4) comprises a polyhydroxyalkanoate and poly(butylene adipate co-terephthalate), preferably consisting of a polyhydroxyalkanoate and poly(butylene adipate co-terephthalate).

5. A film (1) according to claim 4, wherein the second layer (5) consists of 100% w / w polybutylene succinate, and wherein the first layer (4) consists of 26% w / w polyhydroxyalkanoate and 74% w / w poly(butylene adipate co-terephthalate).

6. A film (1) according to claim 4 or 5, wherein the basis weight of the second layer (5) is 25 g / m² 2 is and wherein the basis weight of the first layer (4) is 38 g / m² 2 amounts.

7. A film (1) according to any one of claims 1 to 3, wherein the second layer (5) comprises poly(butylene adipate co-terephthalate) and a lubricant, preferably consisting of poly(butylene adipate co-terephthalate) and a lubricant, and wherein the first layer (4) comprises a polyhydroxyalkanoate and Poly (butylene adipate co-terephthalate) comprises, preferably consisting of a polyhydroxyalkanoate and poly (butylene adipate co-terephthalate).

8. A film (1) according to claim 7, wherein the second layer (5) is composed of 99.5% w / w poly(butylene adipate co-terephthalate) PPONTOOIWO / 10.12.2025 41 and consists of 0.5% w / w of the lubricant, wherein the first layer (4) consists of 26% w / w of a polyhydroxyalkanoate and 74% w / w of poly(butylene adipate co-terephthalate).

9. A film (1) according to claim 7 or 8, wherein the basis weight of the second layer (5) is 25 g / m² 2 is and wherein the basis weight of the first layer (4) is 35 g / m²2 amounts.

10. A film (1) according to any one of claims 1 to 3, wherein the second layer (5) comprises poly(butylene adipate co-terephthalate) and a thermoplastic polyester polyurethane, preferably consisting of poly(butylene adipate co-terephthalate) and a thermoplastic polyester polyurethane, and wherein the first layer (4) comprises a polylactide and polycaprolactone, preferably consisting of a polylactide and polycaprolactone.

11. A film (1) according to claim 10, wherein the second layer (5) consists of 70% w / w poly(butylene adipate co-terephthalate) and 30% w / w thermoplastic polyester polyurethane, and wherein the first layer (4) consists of 80% w / w polylactide and 20% w / w polycaprolactone.

12. A film (1) according to claim 10 or 11, wherein the basis weight of the second layer (5) is 30 g / m² 2 is and wherein the basis weight of the first layer (4) is 30 g / m² 2 amounts .

13. A film (1) according to any one of claims 1 to 3, wherein the second layer (5) is poly(butylene adipate co-terephthalate) PPONTOOIWO / 10.12.2025 42 and a polylactide grafted with maleic anhydride, preferably consisting of poly(butylene adipate co-terephthalate) and a polylactide grafted with maleic anhydride, wherein the first layer (4) comprises a polylactide and polycaprolactone, preferably consisting of a polylactide and polycaprolactone.

14. A film (1) according to claim 13, wherein the second layer (5) consists of 80% w / w poly(butylene adipate co-terephthalate) and 20% w / w polylactide grafted with maleic anhydride, and wherein the first layer (4) consists of 80% w / w polylactide and 20% w / w polycaprolactone.

15. A film (1) according to claim 13 or 14, wherein the basis weight of the second layer (5) is 30 g / m2 and wherein the basis weight of the first layer (4) is 30 g / m2 .

16. A film (1) according to any one of claims 1 to 15, wherein - the first layer (4) comprises at least one first polyester, preferably selected from the group consisting of: polyhydroxyalkanoates, polylactides, poly(butylenesuccinate co-adipate), poly(butylenesuccinate co-terephthalate), polyglycolic acid, polyesteramides, poly(sebacic acid) and copolymers thereof; more preferably selected from the group consisting of polyhydroxyalkanoates and polylactides; and - the second layer (5) comprises at least one second polyester, preferably selected from the group consisting of: polybutylene succinate and poly(butylene adipate co-terephthalate) and copolymers thereof. PPONTOOIWO / 10.12.2025 43 17. A film (1) according to claim 16, wherein the second polyester is present in a mass fraction of at least 60% w / w, preferably at least 70% w / w, particularly preferably at least 80% w / w, based on the total weight of the second layer.

18. A film (1) according to any one of claims 1 to 17, wherein - the first polyester is a polyhydroxyalkanoate and the second polyester is polybutylene succinate; - the first polyester is a polyhydroxyalkanoate and the second polyester is poly(butylene adipate co-terephthalate); or - the first polyester is a polylactide and the second polyester is poly(butylene adipate co-terephthalate).

19. A film (1) according to any one of claims 1 to 18, wherein the polyhydroxyalkanoate is selected from the group consisting of polyhydroxybutyrate, polyhydroxyvalerate, polyhydroxybutyrate-co-valerate and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate).

20. A film (1) according to any one of claims 1 to 19, wherein - the first layer (4) comprises at least one further polymer selected from the group consisting of: poly(butylene adipate co-terephthalate) and polycaprolactone; and / or - the second layer (5) comprises at least one further polymer selected from the group consisting of: thermoplastic polyester polyurethanes and polylactides.

21. A film (1) according to any one of claims 1 to 20, wherein the first polyester is a biodegradable polyester and / or the second polyester is a biodegradable polyester PPONTOOIWO / 10.12.2025 44 is .

22. A film (1) according to any one of claims 1 to 21, wherein the film (1) consists of at least 90%, preferably at least 95%, more preferably at least 98%, most preferably 100% biodegradable materials.

23. A film (1) according to any one of claims 1 to 22, wherein the film is applied to a surface (2), preferably a wood surface or a natural fiber surface, more preferably a surface (2) of a veneer (3), at a temperature of 120 °C to 130 °C and a pressure of 8.4 N / cm². 2 A foil (1) pressed on for 60 s exhibits hot water tightness, wherein the hot water tightness is characterized in that no water penetrates the surface (2) after the foil (1) has been exposed to a 3 cm high column of water for 5 min, wherein the water temperature at the beginning of this period was approximately 100 °C and during this period was in the range of 70 °C to 100 °C.

24. A film (1) according to any one of claims 1 to 23, wherein the film is applied to a veneer (3) at a temperature of 120 °C to 130 °C and a pressure of 8.4 N / cm². 2The film (1) pressed on for 60 s exhibits a peel resistance of at least 0.5 N / mm, preferably at least 0.6 N / mm, measured with a 180° peel test according to DIN EN ISO 8510- 2 : 2010-12.

25. A semi-finished product comprising (6): - a film (1) according to any one of claims 1 to 24; and - a substrate (7) with a surface (2) , preferably a wood surface or a natural fiber surface, PPONTOOIWO / 10.12.2025 45 even more preferably the substrate (7) is a veneer (3) with a surface (2) ; wherein the second layer (5) of the foil (1) is the layer facing the substrate (7) and is materially bonded to the surface (2) of the substrate (7).

26. A sealed product comprising a film (1) according to any one of claims 1 to 24, wherein at least one surface (2), preferably a wood surface or a natural fiber surface, of the sealed product is sealed by the film (1) and the sealed product is selected from the group consisting of: - Disposable products, preferably selected from the group consisting of disposable plates, disposable cups, disposable cutlery, disposable drinking straws, disposable flower pots and disposable boxes; - Products that need to be replaced regularly, preferably selected from the group consisting of cutting boards, trays and surfaces used in exhibition stand construction; and - durable products, preferably selected from the group consisting of furniture fronts, appliance coverings, parquet flooring, interior home finishing products, insulation underlays and vehicle construction products.

27. Method for producing a multilayer film (1), preferably a film (1) according to any one of claims 1 to 24, the method comprising the steps: - Providing an initial raw material; - Providing a second raw material; and - Manufacturing the multilayer film (1) - by co-extrusion, preferably in the form of a blown tube extrusion or slotted extrusion, of the first raw material and the second raw material, wherein a first layer (4) is formed from the first raw material PPONTOOIWO / 10.12.2025 46 and a second layer from the second raw material (5) arises; or - by producing a first film from the first raw material, preferably by blown film extrusion or slotted film extrusion; producing a second film from the second raw material, preferably by blown film extrusion or slotted film extrusion; and laminating the first film and the second film, wherein a first layer (4) is formed from the first film and a second layer (5) is formed from the second film; wherein - the second layer (5) has a melting interval - with a starting temperature greater than 80 °C, preferably greater than 90 °C, even more preferably greater than 95 °C, most preferably greater than 100 °C; and - with an endpoint of less than 170 °C, preferably less than 160 °C, more preferably less than 155 °C, most preferably less than 150 °C, wherein the endpoint is a higher temperature than the starting point; and - the first layer (4) has a melting interval with a starting point that is at least 10 °C, preferably at least 15 °C, most preferably at least 20 °C above the end point of the melting interval of the second layer.

28. A method according to claim 27, wherein the first layer (4) has a melting interval with a starting point that is at most 50 °C, preferably at most 40 °C, most preferably at most 35 °C above the endpoint of the Melting interval of the second layer (5) lies. PPONTOOIWO / 10.12.2025 47 29. Method for producing a semi-finished product (6), preferably a semi-finished product (6) according to claim 25, the method comprising the steps: - Producing a multilayer film (1) by a method according to claim 27; or providing a film (1) according to any one of claims 1 to 24; - Providing a substrate (7) with a surface (2), preferably a wood surface or a natural fiber surface, more preferably the substrate (7) is a veneer (3) with a surface (2); and - Connecting the substrate (7) to the film (1), preferably by means of - a dry laminating system, preferably selected from the group consisting of: roller calender, double belt calender and film laminator; or - a heated press; whereby - the second layer (5) is the layer facing the substrate (7), the second layer (5) is melted, and the second layer (5) is pressed onto the surface (2) of the substrate (7) under pressure and, in its molten state, penetrates at least partially into the surface (2); and - the first layer (4) is not melted.

30. Use of a film (1) according to any one of claims 1 to 24 for sealing a surface (2), preferably a wood surface or a natural fiber surface, more preferably a surface (2) of a veneer (3), against liquids at a temperature of at least 80 °C, preferably at least 90 °C, particularly preferably at least 100 °C PPONTOOIWO / 10.12.2025 48 31. Use of a film (1) according to one of claims 1 to 24 and / or a semi-finished product (6) according to claim 25 for the manufacture - a disposable product, preferably selected from the group consisting of disposable plates, disposable cups, disposable cutlery, disposable drinking straws, disposable flower pots and disposable boxes; - a product that needs to be replaced regularly, preferably selected from the group consisting of cutting boards, trays and surfaces used in exhibition stand construction; or - a durable product, preferably selected from the group consisting of furniture fronts, appliance coverings, parquet flooring, home interior finishing products, insulation underlays and vehicle construction products.

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