Multilayer deep-drawable packaging material

Abstract

The invention relates to a multilayer deep-drawable packaging material with an upper and a lower face, comprising at least one first and a second paper layer and at least one polymer layer. The at least one first and second paper layer are connected together by the at least one polymer layer, and the at least one polymer layer contains at least one water-soluble thermoplastic polymer. The invention additionally relates to a method for producing a multilayer deep-drawable packaging material, having the following steps: (a) providing a first paper layer; (b) applying a polymer layer onto the first paper layer; (c) connecting the first paper layer with the polymer layer applied thereon to a second paper layer such that the polymer layer is located between the first and second paper layer; or (a') providing a second paper layer; (b') applying a polymer layer onto the second paper layer; and (c') connecting the second paper layer together with the polymer layer applied thereon to a first paper layer such that the polymer layer is located between the first and second paper layer, wherein the polymer layer in step (b) contains at least one water-soluble and thermoplastic polymer. The invention additionally relates to the use of the multilayer deep-drawable packaging material according to the invention for producing packages, in particular food packages.

Description

[0001] Multilayer thermoformable packaging material. The subject matter of the invention is a multilayer thermoformable packaging material, a process for its production, and the use of the packaging material for the production of packaging, in particular food packaging. In the field of web-like packaging materials, paper-based products are used for many applications. This is often done when the barrier properties of the packaging material are low, without further modifications, such as the application of synthetic polymer coatings or synthetic polymer films. With the help of synthetic polymer coatings, packaging papers are given barrier properties against oxygen, water vapor, oil, grease, and other substances.The demands placed on such packaging materials by the food industry, especially for sensitive products, are very high and have generally been met by incorporating synthetic polymer coatings, polymer films, or aluminum foils into the multilayer packaging material. Social developments in recent years have led to a growing rethink in the area of ​​packaging materials. One market demand of packaging material manufacturers is to use more environmentally friendly and recyclable materials based on paper and renewable raw materials wherever possible. A major challenge for food packaging manufacturers is to achieve the required high barrier properties while simultaneously providing a particularly environmentally friendly and recyclable packaging material. 211096WO RK / bn20.April 2023 This also applies, and in particular, to packaging materials that are formed using deep-drawing processes due to the requirements for the shape of the packaging material. Such deep-drawable packaging materials are described, for example, in EP 2586606 A1 and are typically composed of at least two paper layers bonded to a layer of a thermoplastic, water-insoluble polymer. Under the influence of pressure and temperature, the packaging material is deep-drawn, and the thermoplastic, water-insoluble polymer retains its shape after cooling. Thus, after applying an additional barrier layer made of a synthetic polymer that is also water-insoluble, trays and plates for cold cuts and other foods can be produced.A disadvantage of these thermoformable packaging materials is that at least one of the essentially water-soluble paper layers in the multilayer thermoformable packaging material is sandwiched between two synthetic, water-insoluble polymer layers. This makes recycling the packaging material after use very complex, making it practically impossible to recycle, making it costly and therefore fundamentally uneconomical. As a result, recycling of such thermoformable packaging materials rarely occurs in practice. State-of-the-art solutions that are intended to enable the removal of the synthetic polymer layer via a punched edge at the edges of the packaging material have proven impractical.Furthermore, while these theoretically allow for the separation of multilayer thermoformable packaging materials, the fundamental use of synthetic, water-insoluble polymers in the packaging material cannot be avoided. Furthermore, despite the separability of the individual components, such thermoformable packaging materials cannot be easily recycled or composted. werden. R K / bn 211096WOApril 20, 2023 Against the background of the prior art, the object of the invention was to provide a multilayer, thermoformable packaging material that does not have the disadvantages of the prior art and, in particular, meets the required high barrier properties for use as food packaging and, at the same time, is easy to recycle and, if appropriate, compost. This object was achieved by a multilayer, thermoformable packaging material with a top and a bottom side, comprising at least a first and a second paper layer and at least one polymer layer, wherein the first and second paper layers are bonded to one another by the at least one polymer layer, characterized in that the at least one polymer layer contains at least one water-soluble thermoplastic polymer.It has surprisingly been found that the use of a water-soluble thermoplastic polymer in the at least one polymer layer connecting the first and second paper layers results in a thermoformable packaging material that meets the high stability required for use as food packaging and, at the same time, is easy to recycle due to the water solubility of the thermoplastic polymer used. In particular, the polymer layer can be completely dissolved by water, and the two paper layers can thus be easily separated from it and recycled. The packaging material according to the invention has a top and a bottom side. The "top side" of the packaging material according to the invention refers to the side that, in later use, comes into contact with the product to be packaged, for example, a food product.The upper side of the packaging material according to the invention is formed by the at least one first paper layer.R. K / bn 211096WOApril 20, 2023 The "underside" of the packaging material according to the invention is understood to mean the side opposite the top side of the packaging material according to the invention. The underside of the packaging material according to the invention is formed by at least one second paper layer and represents the outer side of the packaging in later use. This can optionally be prepared for printing. The multilayer thermoformable packaging material according to the invention comprises at least a first and a second paper layer. According to the invention, a paper layer is understood to mean a layer of paper. Paper within the meaning of the invention is either a base paper or a coated base paper. The term base paper is understood here to mean an uncoated or surface-sized paper.In addition to cellulose fibers, a base paper may contain sizing agents such as alkyl ketone dimers, fatty acids and / or fatty acid salts, epoxidized fatty acid amides, alkenyl or alkyl succinic anhydride, wet strength agents such as polyamine-polyamide-epichlorohydrin, dry strength agents such as anionic, cationic, or amphoteric polyamides or cationic starches, optical brighteners, fillers, pigments, dyes, defoamers, and other auxiliaries known in the paper industry. The base paper may be surface-sized. Suitable sizing agents include, for example, polyvinyl alcohol or oxidized starch. The base paper can be produced on a Fourdrinier or Yankee paper machine (cylinder paper machine). The basis weight of the base paper is preferably 30 to 300 g / m², in particular 60 to 250 g / m², particularly preferably 100 to 220 g / m². The base paper can be used in uncompacted or compressed form (smoothed).Particularly suitable are base papers with a density of 0.8 to 1.2 g / cm3, preferably 0.90 to 1.1 g / cm3.R. K / bn 211096WOApril 20, 2023. Examples of pulp fibers that can be used include bleached hardwood kraft pulp (LBKP), bleached softwood kraft pulp (NBKP), bleached hardwood sulfite pulp (LBSP), or bleached softwood sulfite pulp (NBSP). Pulp fibers obtained from paper waste can also be used. The aforementioned pulp fibers can also be used as a mixture and may optionally contain portions of other fibers, such as synthetic resin fibers. However, pulp fibers made from 100% hardwood pulp are preferably used. The average fiber length of the unrefined pulp is preferably 0.6 mm to 0.85 mm (Kajaani measurement). Furthermore, the pulp preferably has a lignin content of less than 0.05 wt.%, in particular 0.01 to 0.03 wt.%, based on the pulp mass.For example, kaolins, calcium carbonate in its natural forms such as limestone, marble, or dolomite, precipitated calcium carbonate, calcium sulfate, barium sulfate, titanium dioxide, talc, silica, aluminum oxide, and mixtures thereof can be used as fillers for the base paper. In a further embodiment of the invention, the paper layer can consist of a coated base paper. In a coated base paper, at least one pigment-containing layer is arranged on at least one side of the base paper. A metal oxide, silicate, carbonate, sulfide, or sulfate can be used as the pigment. Pigments such as kaolins, talc, calcium carbonate, and / or barium sulfate are particularly suitable. In a further embodiment of the invention, a pigment mixture consisting of the aforementioned calcium carbonate and kaolin can be used for the pigment-containing layer. The calcium carbonate / kaolin ratio is preferably 30:70 to 70:30.The binder / pigment ratio in the pigment-containing layer can be 0.1 to 2.5, preferably 0.2 to 1.5, but especially about 0.9 to 1.3. Any known water-soluble and / or water-dispersible binder can be used in the pigment-containing layer. R. K / bn 211096WO April 20, 2023, in addition to latex binders, film-forming starches such as thermally modified starches, especially corn starches or hydroxypropylated starches. The pigment-containing layer can be applied inline or offline using all application units customary in papermaking, the application rate preferably being selected such that, after drying, the application weight is 0.1 to 30 g / m2, in particular 1 to 20 g / m2, or according to a particularly preferred embodiment 2 to 8 g / m2. beträgt.In a preferred embodiment, the pigment-containing layer is applied using a size press or film press integrated within the paper machine. The paper layer is based essentially on renewable raw materials, such as cellulose and cellulose derivatives. The paper, and thus the paper layer, can have a basis weight of 30 to 300 g / m², in particular of 60 to 250 g / m², particularly preferably of 100 to 220 g / m². According to a preferred embodiment of the invention, the at least one first paper layer and the at least second paper layer are uncoated base papers. According to an alternative preferred embodiment of the invention, the at least one first paper layer is an uncoated base paper and the at least second paper layer is a coated base paper.According to a further alternative preferred embodiment of the invention, the at least one first paper layer and the at least second paper layer are coated base papers. The packaging material according to the invention comprises at least one polymer layer, wherein the first and second paper layers are formed by the at least oneR. K / bn 211096WOApril 20, 2023 Polymer layer are bonded to one another, i.e., the at least one polymer layer is located in the packaging material according to the invention between the first and second paper layers and preferably has full-surface contact with the first and second paper layers. The at least one polymer layer contains at least one water-soluble thermoplastic polymer. The at least one polymer layer can also contain a mixture of water-soluble thermoplastic polymers. Water-soluble within the meaning of the invention means that at least 25% (m / m) of polymer is clearly soluble in water, so that no clouding is visually detectable. In particular, the water-soluble polymers have a water solubility of at least 35% (m / m) in the pH range from 3 to 11, particularly preferably at least 55% (m / m), in particular at least 65% (m / m), very particularly preferably at least 75% (m / m), in particular 100% (m / m).All data on water solubility for all water-soluble thermoplastic polymers used according to the invention refer to standard conditions of 20±5 °C and standard air pressure of 1013.25 hPa. The value (m / m) means mass fraction of polymer based on mass fraction of water. A thermoplastic polymer is understood to be a linear or branched polymer which has no chemical crosslinking points, i.e. covalent bonds, between individual polymer chains. In the case of an amorphous thermoplastic polymer, a thermoplastic polymer is in principle flowable above the glass transition temperature (Tg), and in the case of a (semi-)crystalline thermoplastic polymer, above the melting temperature (Tm). A thermoplastic polymer can therefore be processed into molded parts in the softened state by pressing, extrusion, injection molding, or other shaping processes. K / bn 211096WOApril 20, 2023. A thermoplastic polymer (thermoplastic) can be distinguished from the two other major polymer classes, elastomers and thermosets, which both have chemical crosslinking points, i.e., covalent bonds, between individual polymer chains, via the different temperature curve of the shear modulus G (also known as shear modulus G). The determination of the shear modulus G as a function of temperature can be carried out using conventional methods known to those skilled in the art, for example, using dynamic mechanical thermal analysis (DMTA). The proportion of the water-soluble thermoplastic polymer in the at least one polymer layer is preferably at least 90 wt. %, more preferably at least 95 wt. %, most preferably 98 wt. %, in particular 99 wt. %, based on the total weight of the polymer layer (dry).According to a particularly preferred embodiment of the invention, the polymer layer consists of the water-soluble thermoplastic polymer. In addition to the water-soluble thermoplastic polymer, the at least one polymer layer can contain up to 10 wt. %, preferably up to 5 wt. %, more preferably up to 2 wt. %, more preferably up to 1 wt. %, most preferably 0 wt. %, of further components, based on the total weight of the polymer layer (dry). Further components can be conventional additives that are added to the thermoplastic polymers to improve processability. According to a preferred embodiment of the invention, the at least one water-soluble and thermoplastic polymer has a modulus of elasticity of at least 0.3 GPa, preferably 0.5 GPa, more preferably 0.8 GPa.The Young's modulus is related to the shear modulus G and is determined by tensile testing with the Lorentzen & Wettre Tensile Tester, as described below in connection with the examples. It has been found that the thermoformability of the packaging material according to the invention is improved when R. K / bn 211096WOApril 20, 2023, whose polymer layer contains at least one water-soluble thermoplastic polymer having the above-mentioned modulus of elasticity. According to a further preferred embodiment of the invention, the at least one water-soluble and thermoplastic polymer is a biopolymer or a mixture of biopolymers, in particular a biopolymer selected from modified and natural biopolymers and mixtures thereof. As used herein, a biopolymer is understood to mean a polymer that was produced from renewable raw materials (natural biopolymer), occurs in the natural polymer (natural biopolymer), occurs in nature as a polymer and has been subsequently chemically and / or physically modified (modified biopolymer).The biopolymer is preferably selected from the group consisting of polysaccharides, in particular thermoplastic starch (TPS), polylactides (PLA), polyhydroxybutyrates (PHB), lignin-based thermoplastic polymers, polyvinyl alcohols (PVOH), and ethylene-vinyl alcohol copolymers (EVOH), based on renewable raw materials, for example from cane sugar, and mixtures thereof. The use of a biopolymer as a water-soluble thermoplastic polymer increases the recyclability of the packaging according to the invention and allows its compostability. It goes without saying that these effects increase with increasing proportion of the biopolymer in the at least one water-soluble thermoplastic polymer. According to a particularly preferred embodiment of the invention, the proportion of synthetic polymers in the packaging material is less than 20 wt.%, preferably less than 10 wt.%, particularly preferably less than 5 wt.%, based on the total weight of the packaging material (dry).Synthetic polymers include both water-soluble thermoplastic polymers based on mineral oil, whichR. K / bn 211096WOApril 20, 2023 are not biopolymers, as well as other conventional thermoplastic polymers based on mineral oil, which are predominantly insoluble in water. The application weight (dry weight) of the at least one polymer layer in the packaging material according to the invention can be in the range from 1 to 50 g / m², in particular in the range from 10 to 30 g / m². For some applications, it may be desirable to improve the barrier properties of the packaging material according to the invention. This can be achieved in the packaging material according to the invention by providing a functional layer on the upper side of the packaging material, which in later use comes into contact with the packaged product. A functional layer can, for example, comprise or consist of a layer of a water-insoluble thermoplastic polymer, a water-insoluble thermoplastic polymer film, or an aluminum foil.It has proven particularly practical for improving the barrier properties of the packaging material according to the invention if the functional layer comprises or consists of a layer of a water-insoluble thermoplastic polymer or a water-insoluble thermoplastic polymer film. The water-insoluble synthetic polymer or the water-insoluble synthetic polymer film is preferably selected from the group consisting of PE, PP, PVOH, EVOH, PLA, and mixtures thereof. The provision of a functional layer is particularly advantageous when the product to be packaged, e.g., a food product, is moist, in order to prevent moisture from penetrating the packaging material and thus softening it. According to a preferred embodiment of the invention, the water-insoluble thermoplastic polymer for the functional layer consists of PE and / or EVOH from renewable raw materials, for example, sugar cane.This is advantageous because the use of fossil fuels can be avoided.R. K / bn 211096WOApril 20, 2023 Water-insoluble in the sense of the invention means that the water-insoluble thermoplastic polymer has a water solubility of at most 2% (m / m), particularly preferably 0% (m / m), in water at 25°C. According to a particularly preferred embodiment of the invention, the oxygen permeation of the packaging material is not more than 15 cm3 / m2 in 24 hours, measured according to DIN 53380-3 at a temperature of 23°C, 50% relative humidity, and an air pressure of 1 atm. This advantageously leads to an extended shelf life of a product to be packaged with the packaging material according to the invention, e.g. a food product. According to a further particularly preferred embodiment of the invention, the water vapor permeation of the packaging material is not more than 50 g / m2 in 24 hours, measured according to EN ISO 15106-3 at a temperature of 23°C, 50% relative humidity and an air pressure of 1 atm.It has been found that this embodiment of the packaging material according to the invention protects a moist product to be packaged, e.g., a moist food, from drying out and, on the other hand, protects a dry product to be packaged, e.g., a dry food, from moisture. Overall, this results in an extended shelf life of the respective product to be packaged. erzielt. The packaging material according to the invention preferably has a basis weight of 150 to 600 g / m², in particular of 300 to 500 g / m². Such a basis weight ensures sufficient stability of the packaging material against impacts, so that the occurrence of holes in the packaging, which could impair the shelf life of the goods packaged therein, can be avoided during everyday handling. The multilayer thermoformable packaging material according to the invention has a recyclability of more than 13 scoring points (limited), preferably of R K / bn 211096WOApril 20, 2023, more than 16 scoring points (good), determined according to the recyclability assessment specified below, in accordance with the procedure described in project no. 530592 of the bifa Environmental Institute with the project title "Recyclability of Packaging" (bifa Environmental Institute (2019): Recyclability of Packaging. Specification of the Investigation Framework and Criteria Catalog. In collaboration with Tschachtli S., Pitschke T., Kreibe S., Martin A., Ed. of INTERSEROH Dienstleistungs GmbH, Augsburg; available online at: https: / / www.interseroh.de / fileadmin / Verpackungsoptimierung / 530592_Recyclingfaehigkeit_Bewertungskatalog_v6_3_Download.pdf, checked on 30.03.2020). The invention further relates to a process for producing a multi-layer thermoformable packaging material, comprising the following Schritte:(a) Providing a first paper layer; (b) Applying a polymer layer to the first paper layer; (c) Bonding the first paper layer with the polymer layer applied thereto to a second paper layer such that the polymer layer is located between the first and second paper layers befindet, oder (a') providing a second paper layer; (b') applying a polymer layer to the second paper layer; (c') bonding the second paper layer with the polymer layer applied thereto to a first paper layer such that the polymer layer is located between the first and the second paper layer befindet wherein the polymer layer in step (b) and step (b') contains at least one water-soluble thermoplastic polymer.R K / bn 211096WOApril 20, 2023. The features described in connection with the method according to the invention apply accordingly to the same features already described above in connection with the packaging material according to the invention. The method according to the invention for producing a multilayer thermoformable packaging material provides for the provision of a first paper layer in step (a) and the provision of a second paper layer in step (a'). The first paper layer or second paper layer can be designed as already explained in detail in connection with the packaging material according to the invention. The provision can, for example, comprise the production of the paper in a paper machine and the feeding of the paper into an extrusion coating system.After completion, the paper is wound up in the reeling section of the paper machine, the paper roll is transported to the extrusion coating system, clamped in the extrusion coating system, and continuously unwound. The process according to the invention provides for the application of a polymer layer to the first paper layer in step (b) and the application of a polymer layer to the second paper layer in step (b'), wherein the polymer layer in steps (b) and (b') contains at least one water-soluble thermoplastic polymer. The design(s) of the polymer layer and the water-soluble thermoplastic polymer are as already stated above in connection with the packaging material according to the invention. The application of the polymer layer can be carried out in an extrusion coating system by means of extrusion or co-extrusion. erfolgen.Step (c) of the method according to the invention provides for bonding the first paper layer with the polymer layer applied thereon to a second paper layer, such that the polymer layer is located between the first and second paper layers. Step (c') of the method according to the invention provides for bonding the second paper layer with the polymer layer applied thereon. K / bn 211096WO April 20, 2023 Polymer layer with a first paper layer, such that the polymer layer is located between the first and second paper layers. The bonding of the first and second paper layers according to step (c) or (c') can be carried out simultaneously or after the application of the polymer layer according to step (b) or (b'). erfolgen.According to a preferred embodiment of the invention, before or after step (a) or during or after step (b) or after step (c) or before or during step (c'), a functional layer is applied to the upper side of the first paper layer, which in later use has contact with the product to be packaged. The functional layers mentioned above in connection with the packaging material according to the invention can be used as the functional layer. According to a particularly preferred embodiment, a layer made of a water-insoluble thermoplastic polymer or a water-insoluble thermoplastic polymer film is used as the functional layer. The functional layer can be applied using conventional methods known to those skilled in the art. The functional layer is preferably applied by (co)extrusion or curtain coating. It has proven particularly practical to apply the functional layer by curtain coating.Before or after step (c) or before step (a') or after step (c'), the printing of the underside of the second paper layer, which forms the visible side of the packaging in later use, can take place. If a functional layer is present on the upper side of the first paper layer, the printing of the underside of the second paper layer preferably takes place after the application of the functional layer. Finally, the invention also relates to the use of the multilayer thermoformable packaging material according to the invention for the production of packaging, in particular food packaging.R. K / bn 211096WOApril 20, 2023 The invention is further explained below with reference to the following figures and examples. Fig. 1 Schematic representation of an embodiment of the multilayer thermoformable packaging material according to the invention. Figure 1 schematically shows an embodiment of the multilayer thermoformable packaging material 1 according to the invention. The packaging material 1 according to the invention has a top side 2 and a bottom side 3 and comprises a first paper layer 4 and a second paper layer 5 as well as a polymer layer 6. The top side 2 is in contact with the product to be packaged, for example, a food product, in the later application. The bottom side 3 is the visible side of the packaging material in the later application and can be provided with a print. The first paper layer 4 and the second paper layer 5 have, for example, a basis weight between 30 and 300 g / m².The first paper layer 4 and the second paper layer 5 are bonded to one another by the polymer layer 6. The polymer layer has, for example, an application weight (dry) of 1 to 50 g / m². The polymer layer 6 contains or consists of a water-soluble thermoplastic polymer, in particular a biopolymer. The first paper layer 4 has a functional layer 7 on its upper side. The functional layer 7 has, for example, an application weight (dry) of 1 to 50 g / m² and contains or consists of a water-insoluble thermoplastic polymer, in particular PE, PP, PVOH, EVOH, PLA, and mixtures thereof. Example: The food-compliant base paper used is FibreForm 200 from BillerudKorsnäs with a basis weight of 200 g / m². To produce a packaging material according to the invention, the two food-compliant base paper webs are bonded together by means of a polymer layer of an R. K / bn 211096WOApril 20, 2023 water-soluble thermoplastic polymer, in this example a polyvinyl alcohol (Mowiflex C 30 from Kuraray), in an extrusion coating system. The application weight of the polyvinyl alcohol layer is 10 g / m2.In the next step, a polyethylene layer is applied as a functional layer to the top surface of the resulting composite material by extrusion. The application weight of the polyethylene layer is 10 g / m². The composite material, with the extrusion-coated top surface, is then passed over a special smooth cooling cylinder. The finished, cooled, multilayer packaging material is removed from the extrusion coating system. The result is a multilayer, thermoformable packaging material with good barrier properties in contact with food that is easily recycled. In particular, the packaging material exhibits a recyclability score of at least 16 points, determined according to the recyclability assessment outlined below, in accordance with the process described in project 530592 of the bifa Environmental Institute, entitled "Recyclability of Packaging."Methods and Standards Oxygen Permeation or Oxygen Transmission Rate (OTR) This test is used to determine the oxygen permeability (permeation of pure oxygen or oxygen gas mixtures, e.g., air) of plastic films and hollow plastic bodies (e.g., packaging containers, plastic pipes, etc.) and thus to assess their suitability for packaging purposes and technical applications. The test is carried out according to DIN 53380-3 and at a temperature of 23°C and a relative humidity of 50%. K / bn 211096WOApril 20, 2023Water vapor permeation or water vapor transmission (WVTR)This test is used to determine the water vapor transmission of plastic films, plastic sheets (sheets), and multilayer structures containing plastic using an electrolysis sensor. The test is carried out according to EN ISO 15106-3. Basis weight The basis weight was determined according to DIN EN ISO 536. Assessment of recyclability The test is carried out according to the method described in project 530592 of the bifa environmental institute with the project title "Recyclability of packaging" for determining the recyclability of PPK packaging (paper, cardboard, cartonboard), PPK composite and FKN (liquid cartonboard) (bifa environmental institute (2019): Recyclability of packaging. Specification of the test framework and criteria catalogue. In collaboration with Tschachtli S., Pitschke T., Kreibe S., Martin A. Ed. of INTERSEROH Dienstleistungs GmbH. Augsburg. Available online at: https: / / www.interseroh.de / fileadmin / Verpackungsoptimierung / 530592_Recyclingfaehigkeit_Bewertungskatalog_v6_3_Download.pdf, checked on 30.03.2020). For the purposes of this test method, recyclability is understood to mean the property of a used or usable product made of paper, cardboard or paperboard to be able to be processed in a waste paper processing plant that complies with recognized technical standards in such a way that the waste paper stock produced allows the trouble-free and cost-efficient production of qualitatively acceptable, waste paper-containing new paper. The criteria used to assess recyclability are: - Defibrillability: Mass fraction of components that cannot be used for paper production, i.e. non-paper product components and residues of non-R. K / bn 211096WOApril 20, 2023, defibrated fiber components. The determination of non-paper product components and defibrability is carried out according to the PTS method PTS-RH 021 / 97, published by the Paper Technology Foundation. - Trouble-free sheet formation, i.e., no sticky impurities and optical inhomogeneities, or cleanliness of the recycled mass fraction usable for paper production. Testing for sticky impurities and optical inhomogeneities is also carried out according to the PTS method PTS-RH 021 / 97. Packaging materials are assigned to product category II (see method for determining recyclability PTS-RH 021 / 97, published by the Paper Technology Foundation (PTS)). This includes waste paper that is primarily used for the production of packaging paper. The quantitative assessment of the recyclability of a packaging is carried out using a scoring model based on scoring points.The starting point for the evaluation is the criteria for assessing recyclability. Within the scoring model, a percentage weighting is specified for the evaluation criteria (see Table 1 below), which is determined independently of the consideration of an individual packaging. The quantitative evaluation of recyclability is carried out in the following steps: - Based on the above-mentioned evaluation criteria according to PTS-RH 021 / 97, the degree of fulfillment of the individual evaluation criteria for the packaging to be examined can initially be qualitatively assessed. - Based on the qualitative assessment of the degree of fulfillment of the packaging to be examined, a graded quantitative evaluation (rating) is carried out between 20 (best rating - level 1) and 0 or KOR. K / bn 211096WOApril 20, 2023 (worst rating - level 5) for each evaluation criterion. The underlying scaling is shown in Table 1 below. - By multiplying the criterion-specific rating of the packaging with the corresponding weighting for the respective criterion, an individual scoring is obtained for each criterion. - By summing all individual scorings, the overall assessment of recyclability is obtained, with the following classification applying: Scoring Points % share Lower limit of classification of Further details on the method and evaluation criteria can be found in the referenced publications. [Pique your readers' interest with a relevant quote from the document, or use this space to emphasize a key point. To place the text box anywhere on the page, simply drag it.] K / bn 211096WO 20 April 2023 Table 1: Scoring model for the quantitative assessment of recyclability reßl. im g a us n, 211096WO RK / bn20. April 2023

[0002] E-ModulThe Young's modulus is determined according to the tensile strength test using the Lorentzen & Wettre Tensile Tester. For this purpose, samples of the synthetic resin layer are cut to a width of 50 mm and a length of 120 mm. The measuring length is set to 100 mm. The measuring speed is 100 mm / min. The thickness and basis weight of the samples are determined and entered into the "Young's modulus" test program of the Lorentzen & Wettre Tensile Tester. The tensile strength test is then performed on the samples. The Young's modulus is determined from the relationship between mechanical stress and strain in the linear range of the stress-strain diagram. Deep-drawability: The deep-drawability and sealability were assessed on a Tiromat 3000 deep-drawing machine from Alfa Laval. The films were formed at a deep-drawing temperature of 110°C, i.e., heating was achieved by contact with a heating plate maintained at 110°C. The sealing was carried out at a temperature of 140°C for a time of 1.5 seconds.It was noted whether a heating plate imprint was visible on the film and whether the seal against the paper was sufficiently high so that the paper web could not accidentally detach from the film.211096WO RK / bn20 April 2023.

Claims

- 1 - Patent Claims 1. Multi-layer thermoformable packaging material having a top and a bottom side, comprising at least a first and a second paper layer and at least one polymer layer, wherein the at least one first and a second paper layer are bonded to one another by the at least one polymer layer, characterized in that the at least one polymer layer comprises at least one water-soluble thermoplastic polymer enthält.

2. Multi-layer thermoformable packaging material according to claim 1, characterized in that the at least one first and second paper layer have a basis weight of 30 to 300 g / m², in particular of 60 to 250 g / m², particularly preferably of 100 to 220 g / m².

3. Multi-layer thermoformable packaging material according to claim 1 or 2, characterized in that the application weight (absolute dry weight) of the at least one polymer layer is in the range of 15 to 50 g / m², in particular in the range of 10 to 30 g / m².

4. Multilayer thermoformable packaging material according to one of the preceding claims, characterized in that the at least one water-soluble thermoplastic polymer in the pH range from 3 to 11 at 20±5 °C and 1013.25 hPa has a water solubility of at least 25% (m / m) polymer in W asser aufweist.

5. Multi-layer thermoformable packaging material according to one of the preceding claims, characterized in that the at least one - 2 - water-soluble thermoplastic polymer has a modulus of elasticity of at least 0.8 GPa.

6. Multilayer thermoformable packaging material according to one of the preceding claims, characterized in that the at least one water-soluble thermoplastic polymer is a biopolymer, in particular a biopolymer selected from modified and natural biopolymers.

7. Multilayer thermoformable packaging material according to claim 6, characterized in that the biopolymer is selected from the group consisting of polysaccharides, in particular thermoplastic starch (TPS), polylactides (PLA), polyhydroxybutyrates (PHB), lignin-based thermoplastic polymers, polyvinyl alcohols or ethylene-vinyl acetate copolymers (EVOH) based on renewable raw materials, and mixtures thereof.8.Multi-layer thermoformable packaging material according to one of the preceding claims, characterized in that the packaging material has a recyclability of more than 13 scoring points, preferably more than 16 scoring points, determined according to the method described in project no. 530592 of the bifa environmental institute with the project title "Recyclability of packaging".

9. Multi-layer thermoformable packaging material according to one of the preceding claims, characterized in that the proportion of paper in the packaging material is greater than 80 wt. %, preferably greater than 90 wt. %, particularly preferably greater than 95 wt. %, based on the total weight of the packaging material.

10. Multi-layer thermoformable packaging material according to one of the preceding claims, characterized in that the oxygen permeation of the packaging material is not more than 15 cm3 / m2 inR. K / bn 211096WO April 20, 2023 - 3 - 24 hours, measured according to DIN 53380-3 at a temperature of 23°C, 50% relative humidity, and an air pressure of 1 atm.

11. Multi-layer thermoformable packaging material according to one of the preceding claims, characterized in that the water vapor permeation of the packaging material is not more than 50 g / m2 in 24 hours, measured according to EN ISO 15106-3 at a temperature of 23°C, 50% relative humidity, and an air pressure of 1 atm.

12. A method for producing a multi-layer thermoformable packaging material, comprising the following steps: (a) providing a first paper layer; (b) applying a polymer layer to the first paper layer; (c) bonding the first paper layer with the polymer layer applied thereto to a second paper layer, such that the polymer layer is located between the first and second paper layers befindet, O der(a') providing a second paper layer; (b') applying a polymer layer to the second paper layer; (c') bonding the second paper layer with the polymer layer applied thereto to a first paper layer such that the polymer layer is located between the first and the second paper layer befindet, wherein the polymer layer in step (b) contains at least one water-soluble and thermoplastic polymer.

13. A process for producing a multi-layer thermoformable packaging material according to claim 12, wherein before or after step (a) or during or after step (b) or after step (c) or before or during step (c') the application of a further polymer layer to the top side of theR K / bn 211096WO April 20, 2023 - 4 - first paper layer, which in the later application has contact with the product to be packaged, comprising at least one water-soluble thermoplastic polymer selected from PVOH, EVOH and mixtures thereof.

14. A process for producing a multilayer thermoformable packaging material according to one of claims 12 or 13, wherein the printing of the underside of the second paper layer, which in the later application forms the visible side of the packaging, takes place before or after step (c) or before step (a') or after step (c').

15. Use of the multilayer thermoformable packaging material according to one of claims 1 to 11 for producing packaging, in particular food packaging.R K / bn 211096WO April 20, 2023

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