CLOSED RAILWAY

Description

[0001] The invention relates to a nail-tight sealing membrane, in particular an under-roof membrane or facade membrane for a closed facade, comprising in this order a first nonwoven layer, a membrane layer and a second nonwoven layer, wherein the first nonwoven layer comprises polypropylene fibers.

[0002] The invention further relates to the use of a multilayer film.

[0003] Underlay membranes are used to make roofs waterproof, snowproof, and dustproof beneath the roof covering. Waterproof underlay membranes are known from the state of the art for this purpose. They have a two-layer structure with a nonwoven carrier layer and a TPU-based sealing layer. Examples include EP 2 592 196 B1, DE 20 2009 007 315 ​​U1, and DE 20 2010 000 934 U1, the latter also describing a three-layer structure with sealing layers arranged on both sides of the carrier layer.

[0004] More than three-layer roofing membranes are known, for example, from DE 10 2017 003 364 A1, which describes an underroof membrane with at least one outer nonwoven layer, at least one inner nonwoven layer and at least one microporous membrane layer based on at least one polyolefinic plastic, wherein the membrane layer is arranged between the outer nonwoven layer and the inner nonwoven layer, and wherein at least one further microporous membrane layer based on a polyolefinic plastic is provided between the outer nonwoven layer and the inner nonwoven layer and that the further membrane layer is separated from the membrane layer by a separating layer.

[0005] One of the problems encountered when ensuring the waterproofing of a roof underlay is that nails or staples are driven onto and through the underlay to attach the counter battens for the roof tiles or to staple the underlay to the roof sheathing boards. This creates holes in the underlay through which water can penetrate into the underlying roof structure.

[0006] A wide variety of solutions are known to address this problem. For example, EP 1 992 761 A1 describes a plastic seal for sealing penetrations in sealing elements, which is manufactured from thermoplastics or thermoplastic elastomers using a thermoplastic foam molding process.

[0007] Another common and standard-compliant way to counter this problem is to install so-called nail sealing tapes between the underlayment and the counter battens. Furthermore, DE 10 2017 004 350 A1 describes a nail-tight underlayment with a top layer facing the weathering side and a nail-tight, at least two-layer structure. The underlayment is waterproof and / or permeable to water vapor. The nail-tight layer structure is bonded to the top layer and has at least one sealing layer and at least one protective layer. A wide variety of materials are described for the individual layers, such as polyolefin plastics such as polypropylene, polyethylene, ethylene-vinyl acetate copolymers, polyethylene terephthalate, thermoplastic elastomers such as thermoplastic polyurethane, foamed polymer dispersions, e.g. based on polyurethanes and / or polyvinyl chloride and / or acrylate.

[0008] The object of the present invention is to create a nail-tight sealing membrane.

[0009] The object of the invention is achieved in the sealing membrane mentioned at the outset in that it comprises all the features of claim 1.

[0010] Furthermore, the object of the invention is achieved by the use of a multi-layer film as a nail-tight under-roof membrane or facade membrane for a closed facade, with all the features of claim 12.

[0011] The advantage here is that the structure of the multilayer film is relatively simple, yet surprisingly, an improvement in nail-tightness was achieved compared to currently available "nail-tight products." The membrane layer can be embedded or arranged between two nonwoven layers of at least essentially the same design, eliminating the need for a separation into a top layer and a nail-tight layer structure, as known from the aforementioned DE 10 2017 004 350 A1.

[0012] The term "nail-tight" is used as defined in DE 10 2017 004 350 A1. Accordingly, a roof underlay is nail-tight if, despite being penetrated by a fastening device such as a nail or staple, it remains watertight as defined by ÖNORM B3647:2005.

[0013] According to a preferred embodiment of the sealing membrane, it is intended that it consists of the first nonwoven layer, the membrane layer, and the second nonwoven layer, thus achieving the aforementioned effects with only a three-layer structure. The sealing membrane can therefore be designed relatively thin within the framework of the relevant standards, which not only saves storage space but also transport volume.

[0014] Although PET fibers would be considered more advantageous as a material for the nonwovens of the sealing membrane due to their temperature resistance, nonwovens made of / with polypropylene fibers surprisingly demonstrated the better / best results in the evaluation of the sealing membrane. For this reason, according to a preferred embodiment of the sealing membrane, the first and second nonwoven layers can also be made of polypropylene fibers.

[0015] According to a further embodiment of the sealing membrane, the first and / or second nonwoven layer may comprise at least two different fiber types. The second fiber type can be used to incorporate mechanical reinforcement into the nonwoven layer(s), which can also provide them with greater (further) tear resistance.

[0016] According to the invention, the second nonwoven layer has a basis weight between 40 g / m2 and 200 g / m2, while the first nonwoven layer has a basis weight between 60 g / m2 and 200 g / m2.

[0017] The waterproofing membrane can thus comprise nonwoven layers with a relatively high degree of fiber density, allowing each nonwoven layer to be inherently denser. Furthermore, this also reduces the degree of fiber mobility within the nonwoven layer, thus avoiding the risk of fibers being entrained into neighboring layers during nailing and creating a kind of wicking / absorption effect.

[0018] According to a further design variant of the sealing membrane, the thermoplastic elastomer can be a foamed thermoplastic elastomer, which allows the total area weight of the underlay membrane to be reduced while maintaining the same total layer thickness.

[0019] In one variant, the foamed thermoplastic elastomer can be a closed-cell elastomer foam. This closed-cell structure can increase the waterproofing of the sealing membrane.

[0020] During the course of tests it was found that a thermoplastic polyurethane is a particularly suitable material for the membrane layer to ensure nail tightness.

[0021] According to one embodiment, the thermoplastic polyurethane is preferably a thermoplastic polyether polyurethane. This can improve the cold flexibility of the sealing membrane, ensuring that the nail-tightness of the underlayment is not compromised even at lower temperatures.

[0022] For the same reasons, according to a further embodiment, the thermoplastic polyurethane may be an aromatic thermoplastic polyether polyurethane.

[0023] According to another embodiment, the thermoplastic polyurethane can be formed from at least one diol and at least one polyol, each formed by reaction with at least one diisocyanate, wherein the molecular ratio of diol / polyol is between 10:1 and 1:10. This makes it possible to influence the proportions of hard and soft segments in the structure of the thermoplastic polyurethane. Within the specified limits, it was found that the membrane layer is still sufficiently flexible to adhere to a nail (or similar) when penetrating it, thus improving nail tightness. On the other hand, it also has greater inherent rigidity, which in turn is advantageous for the mechanical load-bearing capacity of the membrane layer. The latter allows at least one of the nonwoven layers and / or the membrane layer to be made thinner.

[0024] To further improve nail tightness, the first and / or second fleece layer may be hydrophobic.

[0025] To improve nail tightness, the membrane layer can also be connected to the first and / or second nonwoven layer only in certain areas, particularly at specific points. This allows for greater mobility of the membrane layer, which can better prevent tensions in the layer structure, e.g., due to temperature fluctuations. This, in turn, allows the membrane layer to adhere better to penetrating objects, such as nails.

[0026] For a better understanding of the invention, it is explained in more detail using the following figure.

[0027] It shows in a simplified, schematic representation: Fig. 1a section of a roof underlay in cross section.

[0028] By way of introduction, it should be noted that in the variously described embodiments, identical parts are provided with identical reference symbols or component designations. The disclosures contained throughout the description can be applied analogously to identical parts with identical reference symbols or component designations. Furthermore, the positional information chosen in the description, such as top, bottom, side, etc., refers to the directly described and illustrated figure, and these positional information must be applied analogously to the new position in the event of a change in position.

[0029] It should be noted at this point that references to standards are to be understood as meaning the respective standards in the version valid on the filing date of this patent application or the patent application establishing priority, unless otherwise stated.

[0030] In Fig. 1A section of a sub-roof membrane 1 designed as a multi-layer film is shown in cross section.

[0031] The underlayment 1 serves as a second water-draining layer under the roof covering, e.g. with tiles, to protect against drifting, capillary, stagnant and condensate water or dirt.

[0032] In the illustrated embodiment, the underroof membrane 1 rests directly on a roof sheathing 2. The roof sheathing 2 can, for example, be formed from (rough-sawn) wooden boards. On the outside, a batten 3 of a counter batten is shown as an example. The counter batten supports the battens for the roof tiles. The batten 3 is connected to the roof substructure with a fastener, in the example shown a nail 4. For this purpose, the fastener penetrates the underroof membrane 1. To prevent water from penetrating the roof substructure, e.g. the thermal insulation, at the points where the fasteners penetrate, the underroof membrane 1 is designed to be nail-tight. In addition, it is inherently waterproof and permeable to vapor diffusion.

[0033] Waterproof means that the underlayment 1 meets the requirements of EN 13859 Part 1 / 2.

[0034] Vapour permeable means that the water vapour permeability Sd according to EN 13859 Part 1 / 2 is between 0.02 m and 0.5 m.

[0035] It should be noted at this point that the roof structure described is only an example. The roof structure can also be designed differently. Accordingly, the underroof membrane 1 (also referred to as the underlay membrane) can also be a so-called sarking membrane. However, for the purposes of this description, no distinction is made between these terms; instead, these types of roof membranes are subsumed under the term "underroof membrane 1." Furthermore, the multi-layer film can also be a facade membrane for closed facades. All of the following statements regarding the underroof membrane 1 can therefore also be applied to the facade membrane, unless otherwise stated.

[0036] It should also be noted that the sealing membrane according to the invention has a width of at least 0.3 m, in particular between 0.5 m and 2 m. The width is measured at an angle of 90° to the winding direction of the sealing membrane on a roll.

[0037] In the illustrated embodiment, the underlay membrane 1 consists of three layers: a first nonwoven layer 5, a membrane layer 6, and a second nonwoven layer 7. The first nonwoven layer 5 faces the roof sheathing 2 and rests on it (in the case of an underlay membrane, the roof sheathing 2 is not present). The second nonwoven layer 7 faces the weathered side of the underlay membrane 1. The membrane layer 6 is arranged between these two nonwoven layers 5, 7 and ensures watertightness, water vapor permeability, and nail tightness.

[0038] Although the three-layer construction is a preferred embodiment of the under-roof membrane 1, it is also possible for the under-roof membrane 1 to have more than three layers, whereby, unlike the arrangement of the layers directly above each other, as shown in Fig. 1 is shown, the first nonwoven layer 5 is connected to the membrane layer 6 via an adhesive layer 8 and / or the membrane layer 6 is connected to the second nonwoven layer 7 via an adhesive layer 9, as shown in Fig. 1 indicated by dashed lines.

[0039] The first nonwoven layer 5 comprises a nonwoven with polypropylene fibers or consists of a polypropylene fiber nonwoven. If the first nonwoven layer 5 also contains other fibers, these can be selected from a group comprising or consisting of polyester fibers and polyamide fibers. The proportion of polypropylene fibers in the first nonwoven layer 5 is at least 50 wt.%, in particular at least 70 wt.%, but can also be 100 wt.%. The fibers of the first nonwoven layer 5 are preferably continuous fibers, and the nonwoven is preferably a spunbonded nonwoven. Furthermore, the fibers of the first nonwoven layer 5 can have a fiber fineness between 1.5 dtex and 5 dtex, in particular between 1.7 dtex and 3.5 dtex, according to DIN 53830, Part 3.

[0040] If other fibers are present in the first nonwoven layer 5 in addition to the polypropylene fibers, these can have a reinforcing effect on the first nonwoven layer 5. These additional fibers can be present, for example, as woven fabric reinforcement or as reinforcing mesh, etc., in or within the first nonwoven layer 5. These reinforcing fibers can also be thicker than the polypropylene fibers. For example, the reinforcing fibers of the first nonwoven layer 5 can have an average fiber diameter selected from a range from the thickness of the polypropylene fibers to 0.5 mm.

[0041] The first nonwoven layer 5 can have a layer thickness between 0.25 mm and 0.95 mm, in particular between 0.3 mm and 0.6 mm.

[0042] The first nonwoven layer 5 has a basis weight between 60 g / m 2< and 200 g / m 2< , on.

[0043] The polypropylene used in the polypropylene fibers is, in particular, apolar polypropylene. Furthermore, it is preferably homopolypropylene with an MFI of 12 g / 10 min to 25 g / 10 min (Melt Flow Index, ISO 1133).

[0044] Preferably, a polypropylene film is used to produce the polypropylene fibers.

[0045] The second nonwoven layer 7 comprises a nonwoven with polypropylene fibers or consists of a polypropylene fiber nonwoven. If the second nonwoven layer 7 also contains other fibers, these can be selected from a group comprising or consisting of polyester fibers and polyamide fibers. The proportion of polypropylene fibers in the second nonwoven layer 7 is at least 50 wt.%, in particular at least 70 wt.%, but can also be 100 wt.%.

[0046] The fibers of the second nonwoven layer 7 are preferably continuous fibers, and the nonwoven is preferably a spunbonded nonwoven. Furthermore, the fibers of the second nonwoven layer 7 can have a fiber fineness between 1.5 dtex and 5 dtex, in particular between 1.7 dtex and 3.5 dtex, according to DIN 53830, Part 3.

[0047] If other fibers are present in the second nonwoven layer 7 in addition to the polypropylene fibers, these can have a reinforcing effect on the second nonwoven layer 7. These additional fibers can be present, for example, as woven fabric reinforcement or as reinforcing mesh, etc., in or within the second nonwoven layer 7. These reinforcing fibers can also be thicker than the polypropylene fibers. For example, the reinforcing fibers of the second nonwoven layer 7 can have an average fiber diameter selected from a range from the thickness of the polypropylene fibers to 0.5 mm.

[0048] The second nonwoven layer 7 can have a layer thickness between 0.25 mm and 0.95 mm, in particular between 0.3 mm and 0.6 mm.

[0049] The second nonwoven layer 7 has a basis weight between 40 g / m 2< and 200 g / m 2< especially between 40 g / m 2< and 150 g / m 2< , on.

[0050] The polypropylene used in the polypropylene fibers is, in particular, apolar polypropylene. Furthermore, it is preferably homopolypropylene with an MFI of 12 g / 10 min to 25 g / 10 min (Melt Flow Index, ISO 1133).

[0051] Preferably, a polypropylene film is used to produce the polypropylene fibers.

[0052] The second nonwoven layer 7 can be constructed identically to the first nonwoven layer 5. However, the second nonwoven layer 7 is preferably different from the first nonwoven layer 5. In particular, the second nonwoven layer 7 can have a lower basis weight than the first nonwoven layer 5. The membrane layer 6 is formed from a thermoplastic elastomer or a foamed thermoplastic elastomer or consists of a thermoplastic elastomer or a foamed thermoplastic elastomer. For this reason, the term "foamed" is placed in parentheses below, since these statements refer to both foamed and non-foamed thermoplastic elastomers, unless otherwise stated.

[0053] The membrane layer 6 can also be called a foamed film.

[0054] Preferably, the membrane layer 6 is a monolithic thermoplastic (foamed) elastomer layer.

[0055] The layer thickness of the membrane layer 6 can be selected from a range of 20 µm to 100 µm, in particular from a range of 20 µm to 50 µm.

[0056] According to one embodiment of the underlayment 1, the foamed thermoplastic elastomer can be a closed-cell elastomer foam.

[0057] However, it is also possible that the foamed thermoplastic elastomer is an open-cell elastomer foam.

[0058] The thermoplastic elastomer is particularly preferably a (foamed) thermoplastic polyurethane. The thermoplastic polyurethane can be a polyester polyurethane, meaning that polyester polyols have been used in its production. According to another embodiment, however, it can also be provided that the thermoplastic polyurethane is a polyether polyurethane, meaning that polyether polyols have been used in its production.

[0059] It is also possible for the (foamed) thermoplastic polyurethane to be an aliphatic thermoplastic polyurethane. However, according to one embodiment, the (foamed) thermoplastic polyurethane can also be an aromatic thermoplastic polyurethane.

[0060] The thermoplastic polyurethane is preferably of the MDI (methylene di(phenyl isocyanate)) or TDI (toluene diisocyanate) type. The isocyanates of these types that can be used are known to those skilled in the art, e.g., 2,4'-MDI and 4,4'-MDI, 2,4'-TDI, and 2,6'-TDI. In addition to these isocyanates, other isocyanates can also be used, such as 1,5-naphthylene diisocyanate (NDI), p-phenylene diisocyanate (PPDI), and 1,6-hexamethylene diisocyanate (HDI), although these isocyanates are not preferred.

[0061] The thermoplastic polyurethane can be formed from at least one diol and at least one polyol, each formed by reaction with at least one diisocyanate, wherein the molecular ratio of diol / polyol can be between 10:1 and 1:10, in particular 1:6 to 1:8. Preferably, a ratio of diol to polyol is selected such that the hardness of the thermoplastic (foamed) polyurethane according to DIN ISO 7619-1 (3s) is between 70 Shore A and 95 Shore A.

[0062] Possible diols are diols of the general formula HO-(CH 2 )n-OH, with n = 2 to 20, such as ethylene glycol, propanediol-(1,3), butanediol-(1,4) or hexanediol-(1,6), unsaturated diols, such as butenediol-(1,4).

[0063] Possible polyols are polyetherols of the general formula HO-(CH 2 ) n -O-(CH 2 ) m -OH, where n is equal to or unequal to m and n or m = 2 to 20. Other polyols are polyols obtained by reacting alkylene oxides, e.g., propylene oxide, with strong bases such as KOH and, optionally, a glycol. Furthermore, polymerization products of tetrahydrofuran or epoxides, such as epichlorohydrin, ethylene oxides, propylene oxides, butylene oxides, and styrene oxide, can be obtained.

[0064] Such diols and polyols for the production of thermoplastic polyurethanes are known to the person skilled in the art, so that further discussion is unnecessary at this point.

[0065] To foam the thermoplastic elastomer, in particular the thermoplastic polyurethane, a blowing agent selected from a group comprising CO 2 and N 2 can be used. In general, a physical and / or chemical blowing agent can be used to produce the foam structure. Preference is given to physical blowing agents such as, for example, alkanes such as butane, pentane, cyclopentane or octane, carbonyl compounds such as acetone, alcohols such as ethanol, inert gases such as argon, or nitrogen and / or carbon dioxide. As a chemical blowing agent, for example, a blowing agent can be used which releases a gas under (thermal) decomposition. Examples of these are citric acid, bicarbonates or azodicarbonamides.

[0066] The proportion of the blowing agent in the total reaction mixture can be selected from 1 wt.% to 20 wt.%.

[0067] The membrane layer 6 can be produced using conventional film manufacturing processes, optionally by extrusion onto the nonwoven layer(s) 5 and / or 7. However, it can also be produced by foam extrusion, in which case the foamable mixture can also be extruded directly onto the first and / or second nonwoven layer 5, 7. Since foam extrusion is known per se, further explanations are unnecessary. The person skilled in the art is referred to the relevant literature.

[0068] The individual layers of the underlay membrane 1 can also be joined together by ultrasonic welding and / or mechanical bonding, etc. In addition to directly bonding the individual layers, they can also be bonded together with an adhesive.

[0069] Before the individual layers are joined together, it may be advantageous if the first and / or second nonwoven layer 5, 7 is pretreated, for example by means of a corona treatment.

[0070] To further improve nail tightness, it can be provided that the first and / or second nonwoven layer 5, 7 is / are hydrophobicized. To hydrophobize the polypropylene fibers, a hydrophobizing agent can be used that is selected from a group comprising or consisting of alkoxysilanes, e.g., partially hydrolyzed silanes, low-molecular-weight alkylalkoxysiloxanes, octyltriethoxysilane, alkoxysiloxanes, e.g., oligomeric alkylalkoxysiloxanes, alkylpolysiloxanes, e.g., polymeric siloxanes, alkali metal siliconates, e.g., potassium methyl siliconate, or mixtures of the aforementioned groups of substances, such as, e.g., silane-siloxane mixtures.

[0071] The proportion of hydrophobizing agent in the first and / or second nonwoven layer 5, 7 can be selected from a range of 1 wt.% to 30 wt.%, for example from a range of 1 wt.% to 10 wt.%.

[0072] The first nonwoven layer 5 and / or the second nonwoven layer 7 can be connected to the membrane layer 6 over their entire surface, i.e. over the entire adjoining surfaces. According to a preferred embodiment, however, it is also possible for the membrane layer 6 to be connected to the first and / or second nonwoven layer 5, 7 only in certain regions, in particular only at specific points. The connection points can be arranged at a distance from one another that is selected from a range of 0.1 mm to 5 mm. The distance is the shortest distance between any two immediately adjacent connection points. The connection points can be arranged in the form of a grid (square, rectangle, rhombus, etc.).

[0073] To evaluate the roof underlay 1, the following examples were tested, among others. Example 1:

[0074] A sub-roof membrane 1 was produced which had the following structure: Nonwoven layer 5: Polypropylene continuous fiber nonwoven, 75 g / m 2< Adhesive layer 8: Hotmelt adhesive Membrane layer 6: Thermoplastic polyurethane, 25 µm Adhesive layer 9: Hotmelt adhesive Nonwoven layer 7: Polypropylene continuous fiber nonwoven, 75 g / m 2< Example 2 (not according to the invention):

[0075] A sub-roof membrane 1 was produced which had the following structure: Nonwoven layer 5: Polypropylene continuous fiber nonwoven, 75 g / m 2< Adhesive layer 8: Hotmelt adhesive Membrane layer 6: Thermoplastic polyurethane, 25 µm Adhesive layer 9: Hotmelt adhesive Nonwoven layer 7: Polypropylene continuous fiber nonwoven, 30 g / m 2< Example 3:

[0076] A sub-roof membrane 1 was produced which had the following structure: Nonwoven layer 5: Polypropylene continuous fiber nonwoven, 95 g / m 2< Adhesive layer 8: Hotmelt adhesive Membrane layer 6: Thermoplastic polyurethane, 25 µm Adhesive layer 9: Hotmelt adhesive Nonwoven layer 7: Polypropylene continuous fiber nonwoven, 95 g / m 2< Example 4:

[0077] A sub-roof membrane 1 was produced which had the following structure: Nonwoven layer 5: Polypropylene continuous fiber nonwoven, 80 g / m 2< Membrane layer 6. Thermoplastic polyurethane, 100 g / m 2< , a direct coating of the nonwoven layer 5 Nonwoven layer 7: Polypropylene continuous fiber nonwoven, 80 g / m 2< Example 5:

[0078] A sub-roof membrane 1 was produced which had the following structure: Nonwoven layer 5: Polypropylene continuous fiber nonwoven, 80 g / m 2< Membrane layer 6. Thermoplastic polyurethane, 100 g / m 2< , two coatings of 50 g / m each 2< Nonwoven layer 7: Polypropylene continuous fiber nonwoven, 80 g / m 2<

[0079] The nail resistance of these sample underlay membranes was tested using the following test, using 500 mm test samples. The test samples were applied to a rough-sawn roof sheathing with a lap joint. The counter battens were also rough-sawn. The lap joint was glued. Before the test samples were installed, a sheet of colored crepe paper was applied over the entire surface of the roof sheathing. A total of 24 standard nails were then nailed through the roof battens. Test conditions:

[0080] Roof pitch: 14° 5 minutes of running water (8 l / min) 5 minutes of running water (8 l / min) + spraying water (4 l / min) 10 minutes of running water (8 l / min) + spraying water (4 l / min) + wind (12 m / s with fan) 10 minutes of running water (8 l / min) + spraying water (4 l / min) + wind (16 m / s with fan)

[0081] After the test, the battens and underlayment 1 were removed, and a visual inspection of the crepe paper was performed. Water penetration can be detected by a discoloration of the crepe paper. The volume of water penetrated can be determined by the diameter of the discolored area. One water droplet causes a stain with a diameter of 25 mm. Two water drops result in a stain with a diameter of 35 mm, and five water drops result in a stain with a diameter of 50 mm.

[0082] Of the 24 nail spots on the underlay membrane according to Example 1, water penetration was detected in only three of them, with the size of the spots being significantly less than 25 mm in diameter.

[0083] The underlayment 1 can therefore be described as nail-tight.

[0084] Examples 2 to 5 produced similar results, with Example 5 producing a better result than Example 4.

[0085] The embodiments show or describe possible embodiments of the sealing membrane, whereby it should be noted at this point that combinations of the individual embodiments are also possible, within the limits defined by the claims.

[0086] For the sake of clarity, it should finally be pointed out that in order to better understand the structure of the sealing membrane, it or its components are not necessarily shown to scale. Reference symbol list

[0087] 1Sub-roof membrane 2Roof sheathing 3Batch 4Nail 5Fleece layer 6Membrane layer 7Fleece layer 8Adhesive layer 9Adhesive layer

Claims

1. Nail-tight sealing membrane, in particular under-roof membrane (1) or façade membrane, comprising, in this order, a first nonwoven layer (5), a membrane layer (6) and a second nonwoven layer (7), the first nonwoven layer (5) comprising polypropylene fibers and the second nonwoven layer (7) comprising polypropylene fibers and the membrane layer (6) being formed on the basis of a thermoplastic elastomer, the second nonwoven layer (7) having a weight per unit area of between 40 g / m2 and 200 g / m2, and the first nonwoven layer (5) has a weight per unit area of between 60 g / m2 and 200 g / m2, characterized in that the sealing membrane comprises the first nonwoven layer (5), the membrane layer (6) and the second nonwoven layer (7), the first nonwoven layer (5) optionally being bonded to the membrane layer (6) via an adhesive layer (8) and / or the membrane layer (6) optionally being bonded to the second nonwoven layer (7) via an adhesive layer (9).

2. The nail-tight sealing membrane according to claim 1, characterized in that the first and second nonwoven layers (5, 7) consist of polypropylene fibres.

3. The nail-tight sealing membrane according to claim 1, characterized in that the first and / or the second nonwoven layer (5, 7) has at least two different types of fibres.

4. The nail- tight sealing membrane according to one of claims 1 to 3, characterized in that the thermoplastic elastomer is a foamed thermoplastic elastomer.

5. The nail-tight sealing membrane according to one of the claims 4, characterized in that the foamed thermoplastic elastomer is a closed-cell elastomer foam.

6. The nail- tight sealing membrane according to one of claims 1 to 5, characterized in that the thermoplastic elastomer is a thermoplastic polyurethane.

7. The nail-tight sealing membrane according to claim 6, characterized in that the thermoplastic polyurethane is a thermoplastic polyether polyurethane.

8. The nail-tight sealing membrane according to claim 6 or 7, characterized in that the thermoplastic polyurethane is an aromatic thermoplastic polyurethane.

9. The nail-tight sealing membrane according to claim 6 to 8, characterized in that the thermoplastic polyurethane is formed from at least one diol and at least one polyol in each case by reaction with at least one diisocyanate, the molar ratio of diol / polyol being between 10:1 and 1:10.

10. The nail- tight sealing membrane according to one of claims 1 to 9, characterized in that the first and / or the second nonwoven layer (5, 7) is hydrophobized.

11. The nail-tight sealing membrane according to one of claims 1 to 10, characterized in that the membrane layer (6) is only connected to the first and / or the second nonwoven layer (5, 7) in certain areas, in particular only at certain points.

12. Use of a multilayer film comprising, in this order, a first nonwoven layer (5), a membrane layer (6) and a second nonwoven layer (7), the first and second nonwoven layers (5, 7) comprising polypropylene fibers, and wherein the first nonwoven layer (5) has a weight per unit area of between 60 g / m2 and 200 g / m2 and the second nonwoven layer (7) has a weight per unit area of between 40 g / m2 and 200 g / m2, and the membrane layer (6) is formed on the basis of a thermoplastic elastomer, as a nail-tight under-roof membrane (1) or façade membrane for a closed façade, the sealing membrane consists of the first nonwoven layer (5), the membrane layer (6) and the second nonwoven layer (7), the first nonwoven layer (5) optionally being bonded to the membrane layer (6) via an adhesive layer (8) and / or the membrane layer (6) optionally being bonded to the second nonwoven layer (7) via an adhesive layer (9).

13. The use according to claim 12, characterized in that the nail-tight under-roof membrane (1) or façade membrane is formed as a sealing membrane according to one of claims 2 to 11.