DE29602475U1 - Diffusion-open roofing membrane - Google Patents

Description

G96

Description 5

Dr. Paul Spielau 53 844 Troisdorf

Vapour-permeable roof underlay 10

The innovation relates to a diffusion-open roofing membrane that is hydrophobic and/or has been given a hydrophobic finish, containing at least a three-layer composite of nonwoven layers based on thermoplastics, wherein at least the outer nonwoven layers are at least predominantly made of continuous filaments and at least one inner nonwoven layer is at least predominantly made of meltblown microfibers, wherein one or more nonwoven layers are optionally consolidated by pattern embossing.

Roof underlays are laid on roofs beneath the tiles or other covering building blocks to provide additional protection against moisture, dust, drifting snow and wind. They should also be very strong, particularly tear-resistant, and as waterproof and rainproof as possible.

0 For example, roof underlays made of plastic films with or without reinforcement inserts are well known.

A roofing membrane made of a composite of nonwoven layers based on polypropylene is also known, in which the outer nonwoven layers are made of continuous filaments and an inner nonwoven layer is made of melt-blown microfibers, wherein the composite made of the nonwoven layers

is hydrophobic. The roof underlayment thus formed has *- a surface weight of 160 g/m.

The outer fleece layers made of continuous filaments ensure high tear resistance, while the fleece layer made of melt-blown microfibers inside the composite provides a good balance between water resistance and water vapor permeability, so that moisture that forms under the roof can escape to the outside as vapor through the roof underlay. The disadvantages of this well-known roof underlay based on fleece layers are insufficient water resistance, impermeability to driving rain on hard surfaces (for example on shuttered roofs) and a tent effect, which is due to excessive capillary conductivity for water droplets and its sensitivity to impregnating agents, especially water-soluble ones, such as those used for chemical wood protection of the roof structure.

0 The production of nonwoven layers from continuous filaments is described, for example, in US 4340 563. The production of nonwoven layers from melt-blown microfibers is known, for example, from US 3978 185. The production of composites from various nonwoven layers made of fibers and/or filaments made of thermoplastics for breathable and waterproof or water-absorbent textile applications, such as clothing, wipes, etc., is known, for example, from DE-PS 23 56 720.

The known composite materials can be made water-repellent with a suitable hydrophobizing agent, which is described, for example, in US 3837 996.

5 Furthermore, it is known, for example from EP 0245 933, to provide roof underlays with a stable carrier sheet made of a polyester spunbond, which is subsequently bituminized to achieve watertightness.

DE-OS 34 25 794 discloses a roof underlay made of a polyurethane film covered with a fleece layer, for example made of polyester. The introduction to the description of this publication mentions an underlay made of highly tear-resistant polyester spunbond and provided with a water-repellent and breathable special coating in the form of a paste. However, nothing can be learned from this publication about the structure of the polyester fleece used.

EP-PS 0027 750 describes a carrier sheet for a roof underlayment, which consists of a fibre fleece made of polypropylene, polyethylene, polyester or polyvinyl and has a basis weight between 85 and 200 g/m ² .

The aim of the innovation is to further develop a vapor-permeable roof underlay membrane based on fleece layers in such a way that it overcomes the disadvantages of the state of the art 0.

According to the innovation, this task is solved with a vapor-permeable roof underlay membrane according to the characterizing features of claim 1.
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Advantageous embodiments of the innovation can be found in the subclaims.

According to the innovation, a vapor-permeable roof underlay membrane is proposed in which the inner fleece layer made of melt-blown microfibers is hydrophobically treated and has a basis weight of 10 to 100 g/m ² , preferably 20 to 60 g/m ² , and the surface of the inner fleece layer is formed by heat treatment in a film-like manner with residual pores, whereby water vapor permeability is ensured.

A film-like formation of the surface of the inner fleece layer made of meltblown microfibers by means of

Heat treatment can be achieved, for example, by slightly melting the surface of the fleece layer, whereby the melted microfibers spread out over the surface and form a film-like bond, which, however, does not form a closed surface, but rather leaves very fine pores, so-called residual pores. Through the heat treatment, the large pores between the microfibers are closed by melting the microfibers and spreading out over the surface, or are reduced to small residual pores.

Surprisingly, it was found that this film-like surface of the inner fleece layer made of melt-blown microfibers significantly improves the waterproofing, resistance to driving rain and the resistance to chemical wood preservatives of the new roof underlay based on fleece layers. The tent effect caused by capillary action is almost eliminated. The residual pores remaining on the film-like surface of the fleece layer made of melt-blown microfibers are so small that the capillary action against water droplets is eliminated and the water vapor permeability is still maintained.

5 The additional hydrophobic treatment of the inner fleece layer made of melt-blown microfibers further increases the watertightness and resistance to driving rain. Hydrophobing also refers to the water-repellent treatment of the fleece layer, as is known from textile technology 0.

For example, hydrophobic agents based on fluorocarbons, such as block copolymers of a perfluoroalkyl acrylate, are suitable for making the inner layer of melt-blown microfibers hydrophobic. Fluorocarbons that contain trifluoromethylsilyl groups instead of perfluoroalkyl groups are also advantageous.

to achieve the desired hydrophobization of the inner nonwoven layer made of meltblown microfibers.

To form the new roofing membrane, the hydrophobic inner fleece layer made of melt-blown microfibers is covered on the top and bottom by a fleece layer made of continuous filaments in a composite of at least three layers, whereby the composite is produced, for example, by lamination and/or covering. The inner fleece layer made of melt-blown microfibers takes on the function of a waterproof but water vapor-permeable membrane, which is due to the small pore size in the film-like melted surface, as already explained.

The outer fleece layers made of continuous filaments provide a protective function for the inner fleece layer made of melt-blown microfibers against external influences and give the new roof underlay the desired mechanical properties, such as tear resistance and abrasion resistance.

The melting of the surfaces of the inner fleece layer made of melt-blown microfibers by the action of heat can preferably be carried out immediately before lamination with the outer fleece layers to form the new roofing membrane, thereby bringing about another surprising improvement.

0 By melting the surfaces of the inner fleece layer made of melt-blown microfibers immediately before lamination, the new roof underlay membrane enables a surprisingly strong bond with the outer fleece layers of the composite, which does not require the use of high pressures and temperatures during lamination. In this way, the desired water vapor permeability is maintained, since the microfiber structure is partially retained and residual pores on the surface

remain. Nevertheless, the high level of driving rain resistance is achieved by the film-like surfaces and at the same time a very good adhesive bond with the continuous filaments of the outer fleece layers is achieved.
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Furthermore, the new roof underlayment does not require a costly hydrophobic finish on the outer fleece layers, i.e. the composite, since the inner fleece layer made of melt-blown microfibers alone reliably ensures the water-repellent properties of the new roof underlayment through appropriate finishing.

In an advantageous embodiment of the innovation, all layers of the composite are made from polyolefins, in particular polypropylene, wherein the nonwoven layer made of continuous filaments on the inside of the roof facing the building has a basis weight of 17 to 60 g/m ² and the nonwoven layer made of continuous filaments on the outside of the roof has a basis weight of 50 to 80 g/m ² and the inner nonwoven layer (12) made of meltblown microfibers has a basis weight of 10 to 100 g/m ² , preferably 20 to 60 g/m ² .

The structure of the composite made of fleece layers based on the same polyolefin, in particular polypropylene, allows for pure recycling of the new roofing membrane.

Particularly advantageously, the fleece layer made of continuous filaments on the inside of the roof facing the building, which has a lower weight per unit area than the fleece layer made of continuous filaments on the outside of the roof, can be provided with an embossed pattern, whereby this fleece layer is embossed during its production or before lamination using a suitably designed embossing roller, whereby it is solidified on the one hand to improve its mechanical properties and the surface is made uneven and "rough". Surprisingly, it was found that this

embossed surface on the inside of the roof of the new roof underlayment prevents the formation of drops as a result of condensation and thus the vapor permeability of the inner fleece layer made of melt-blown microfibers cannot be impaired by the accumulation of drops on the inside surface of the new roof underlayment.

The nonwoven layer made of continuous filaments on the outside of the roof, on the other hand, can advantageously be consolidated between smooth rollers before lamination, so that no embossed pattern is applied, but an intensive connection of almost all crossing areas of the crossing continuous filaments within the nonwoven layer takes place, whereby this nonwoven layer has a particularly high tear resistance, which is reflected in a high tear resistance of the roof underlay according to the innovation.

In a further advantageous embodiment of the innovation, it is proposed that in order to further improve the mechanical properties inside the composite, adjacent to the inner fleece layer made of melt-blown microfibers, an additional reinforcing insert, such as a scrim, knitted fabric, or fabric made of thermoplastic material, is provided, which in particular further increases the tear resistance of the roof underlay according to the innovation.

Since the surface of the inner fleece layer made of meltblown microfibers is melted under heat before lamination to form the film-like surface, the reinforcing insert is pressed into the microfiber fleece as a result of the pressure exerted during lamination of the composite, so that a firm connection is created between the reinforcing insert and the microfiber fleece and they combine to form a unit.

Likewise, the surfaces of the microfiber fleece melted before lamination create a firm bond with

the outer fleece layers made of continuous filaments, so that the renewed roof underlay membrane has a particularly strong layer bond.

Advantageously, all layers of the new roofing membrane, including the reinforcing insert, are made from polypropylene, so that pure recycling is possible. In addition, the additional reinforcing insert inside the composite increases the tear resistance of the new roofing membrane to such an extent that it is possible to reduce the basis weight of the nonwoven layer made of continuous filaments on the outside of the roof compared to the first-mentioned embodiment of the new roofing membrane without impairing the overall properties of the composite. It is proposed that both outer layers made of continuous filaments have a basis weight of 17 to 60 g/m , the inner nonwoven layer made of melt-blown microfibers has a basis weight of 10 to 100 g/m , preferably 20 to 60 g/m ² , and the reinforcing insert has a basis weight of up to 60 g/m ² .

To further increase the bonding forces between the individual layers, the reinforcement insert can also be provided with a hot melt adhesive, particularly based on ethylene vinyl alcohol (EVA), which, when the composite is laminated, causes the outer fleece layers made of continuous filaments and the inner fleece layer made of 0 meltblown microfibers to bond to the reinforcement insert due to the heat that prevails during the process.

In a further advantageous embodiment of the innovation, the inner fleece layer is made of melt-blown microfibers based on polyurethane, which allows for particularly high

Water vapor permeability values of the new, vapor-permeable roof underlayment can be achieved.

The film-like character of the surface of the polyurethane fleece layer made of melt-blown microfibers as a result of the heat effect before lamination with the outer fleece layers made of continuous fibers results in good waterproofness, resistance to driving rain and resistance to chemical wood preservatives, comparable to a polyurethane film, whereby the tent effect is almost eliminated.

When forming the inner fleece layer from melt-blown polyurethane microfibers, it is advantageously proposed to produce the outer fleece layers from continuous filaments based on polyester, whereby the continuous polyester filaments have a basis weight of 30 to 100 g/m and the inner fleece layer made of melt-blown microfibers based on polyurethane has a basis weight of 10 to 80 g/m ^2. The upper and lower polyester fleece layers provide very good mechanical strength and abrasion resistance and, for example, have better weather resistance, for example against UV rays, than polypropylene. The maximum tensile strength of the fleece layer made of continuous polyester filaments is preferably at least about 100 to 250 N/5 cm, depending on the basis weight. A largely linear polyester urethane is particularly suitable for producing the inner fleece layer from melt-blown polyurethane microfibers. This preferably has an MVI (190 ⁰ C, 10 kg) of 15 to 23 cm ³ /l0 min., a softening range of 60 to 70 ⁰ C according to Kofier and a melting point range of 90 to 150 ⁰ C according to DIN 53460.

This version of the new roof underlayment can also be equipped with a reinforcing insert, such as a mesh or similar, inside the composite in order to further increase the tear resistance and stability of the new roof underlayment. This reinforcing mesh can be made of polyester, for example.

In addition, in accordance with the innovation, it is also possible to create a vapour-permeable roof underlay membrane that has outer fleece layers made of polypropylene continuous filaments and an inner fleece layer made of melt-blown polyurethane microfibres.

The basis weight of the outer nonwoven layers made of polypropylene continuous filaments is advantageously about 30 to 100 g/m ² , while the basis weight of the inner nonwoven layer made of melt-blown polyurethane microfibers is about 10 to 80 g/m ² . 10

In order to comply with the applicable regulations, the new roof underlayment has a tear resistance of at least 120 N/5 cm.

The innovation is explained in more detail below using examples in the drawing.

Fig. la an embodiment of the new

vapour-permeable roof underlay 20

Fig. Ib another embodiment of the new roof underlayment

Fig. 2 shows a schematic representation of an arrangement for producing the new roof underlay membrane

Fig. 3 shows a non-scale section through a roof construction using the new roof underlayment.

According to Fig. la, the roof underlay membrane 1 according to the invention consists of a three-layer composite of nonwoven layers 11, 12, 13, wherein the outer nonwoven layers 11, 13 are formed from continuous filaments and the inner 5 nonwoven layer 12 is formed from meltblown microfibers.

The fleece layer 11 on the inside of the roof is made of continuous filaments based on polypropylene with a weight per unit area of 17 to 60 g/m ² , and this fleece layer is provided with an embossed pattern 14 for reinforcement. For example, this fleece layer has a tear strength of around 20 N/5 cm. Furthermore, this embossed pattern 14 creates a rough surface on the fleece layer 11 on the inside of the roof made of continuous filaments, so that when the roof underlay 1 is placed on a building structure, the formation of water droplets as a result of condensation on the inside of the roof is prevented and the water vapor permeability of the roof underlay 1 according to the innovation cannot be impaired by accumulations of water droplets. The embossed pattern 14 can, for example, have been introduced into the fleece layer 1 made of continuous filaments using an appropriately designed embossing roller before lamination.

A nonwoven layer 12 is applied to this nonwoven layer 11 on the inside of the roof, wherein the nonwoven layer 12 is formed from melt-blown microfibers and is also made on the basis of polypropylene and has a basis weight of 10 to 100 g/m ² , preferably 20 to 60 g/m ² .

The fleece layer 12 made of meltblown microfibers is made hydrophobic in a known manner with a suitable fluorocarbon and the surface of the fleece layer 12 made of meltblown microfibers is formed into a film by heat treatment. This film-like formation of the surface of the inner fleece layer 12 made of meltblown microfibers was created by melting the two surfaces immediately before joining with the other fleece layers. The pores remaining on the film-like surface of the fleece layer 12 made of meltblown microfibers are so small that the capillary effect against water droplets is eliminated, so that the fleece layer 12 made of meltblown microfibers is waterproof but permeable to water vapor. At the same time, the

Behavior towards chemical wood preservatives significantly improved.

A nonwoven layer 13 made of continuous filaments is applied to the nonwoven layer 12 made of melt-blown microfibers, the continuous filaments being based on polypropylene and having a basis weight of 50 to 80 g/m ^2. The nonwoven layer 13 made of continuous filaments, which forms the nonwoven layer on the outside of the roof of the roof underlay membrane 1 according to the invention, is consolidated between smooth rollers before lamination, so that an intensive connection is achieved near all crossing areas of the crossing continuous filaments within the nonwoven layer 13 and the nonwoven layer 13 has a particularly high tear strength of, for example, about 300 N/5 cm and a high abrasion resistance.

In this way, the inner fleece layer 12 made of melt-blown microfibers is covered on both sides by fleece layers 0 11, 13 made of continuous filaments, whereby the layer 13 on the outside of the roof has particularly good mechanical properties, such as high tear resistance and abrasion resistance, while the inner microfiber layer 12 ensures watertightness while at the same time

Water vapor permeability of the new roof underlayment 1 is achieved in a membrane-like manner. To further increase the watertightness, the inner fleece layer 12 made of melt-blown microfibers can also be treated with a suitable hydrophobic agent to make it water-repellent. The fleece layer 11 on the inside of the roof made of continuous filaments also protects the fleece layer 12 made of melt-blown microfibers and prevents the accumulation of water droplets due to its rough surface caused by the embossed pattern 14.

The production of this innovative composite for the roof underlayment 1 is shown schematically in Fig. 2. The individual fleece layers 11, 12, 13 are

not shown in more detail, for example on rolls and unwound from the individual rolls in the direction of arrows Pl, P2, P3 and drawn into a laminating device.
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The laminating device 2 has an upper conveyor belt 20 and a lower conveyor belt 21, whereby the conveyor belts 20, 21 continuously rotate over deflection rollers 23, 24 by means of a drive not shown in detail. A gap is formed between the two rotating conveyor belts 20, 21, into which the fleece layers to be laminated are introduced. The rotating conveyor belts 20, 21 of the laminating device 2 cause the layers to be laminated to pass through the laminating device 2.

Furthermore, the laminating device 2 has heating and cooling units 22 in its interior, which act through the rotating conveyor belts 20, 21 to laminate the fleece layers pulled through the laminating device 2 between the rotating conveyor belts 20, 21. In order to ensure good temperature transfer through the rotating conveyor belts 20, 21, these are made of Teflon or are equipped with a Teflon layer on the side that comes into contact with the layers to be laminated. At the same time, the Teflon surfaces on the rotating conveyor belts 20, 21 prevent the rotating conveyor belts 20, 21 from sticking to the fleece layers.

Furthermore, roller pairs 23 are provided inside the laminating device 2, which can exert sufficient pressure on the fleece layers pulled through the laminating device 2 for lamination. In conjunction with the heating and cooling elements 22, the pressure and heat required for lamination can thus be applied by the laminating device 2, while the fleece layers are pulled through the laminating device 2 by means of the rotating conveyor belts 20, 21.

■&igr; 4

While the outer fleece layers 11, 13 are solidified in a manner not shown, if necessary using appropriate rollers, before lamination, the inner fleece layer 12 is melted on both sides of its surfaces by a heating device (not shown in detail) using heat rays W immediately before it enters the laminating device 2, so that it has film-like surfaces. Immediately afterwards, it is drawn into the laminating device 2, with the outer fleece layers 11, 13 made of continuous filaments being placed on the melted surfaces of the fleece layer 12 made of melt-blown microfibers.

Already at this point, the melted surfaces of the microfiber fleece layer 12 create a connection with the outer fleece layers 11, 13 made of continuous filaments. During the further passage through the laminating device 2, the fleece layers 11, 12, 13 placed on top of one another are grasped by the Teflon-coated rotating conveyor belts 20, 21 and pulled through the laminating device 2. The heating and cooling elements 22 arranged inside the laminating device 2 on the top and bottom of the three-layer composite of the fleece layers 11, 12, 13 apply the heat required for lamination, while the pressure required for lamination is applied to the composite via the pressure rollers 23, so that the roof underlay 1 according to the innovation is formed with a solid composite 0 of the individual fleece layers 11, 12, 13 at the exit of the laminating device 2. At the same time, the inner fleece layer 12 made of melt-blown microfibers has the film-like melted surfaces, whereby the remaining pore size has been reduced in such a way that water impermeability is ensured, while water vapor can still pass through the roof underlay 1. By separately regulating the temperatures of the heating and cooling elements on the top and bottom

the retained properties of the renewed roof underlayment can be optimized.

A further embodiment of the roof underlay membrane according to the innovation is shown in Fig. 1b. In addition to the structure of the roof underlay membrane 1 described in Fig. 1a with a fleece layer 12 made of melt-blown microfibers on the inside and fleece layers 11, 13 made of continuous filaments on the outside, in the embodiment according to Fig. 1b an additional reinforcing insert in the form of a grid 10, for example made of polypropylene, is introduced into the interior of the composite. This reinforcing grid 10 significantly increases the mechanical strength of the roof underlay membrane 1 according to the innovation, but the water vapor permeability of the fleece layer 12 made of melt-blown microfibers is not significantly impaired due to the grid gaps 10a.

The production of this four-layer composite made of two outer fleece layers 11, 13 made of continuous filaments, an additional reinforcing mesh 10 and a fleece layer 12 made of meltblown microfibers inside the composite is carried out in a similar manner to the example already described in Fig. 2, with only the additional reinforcing mesh 10 being fed to the laminating device 2 in a similar manner. Due to the already described melting of the surfaces of the inner fleece layer 12 made of meltblown microfibers, the reinforcing mesh 10 is pressed into the fleece layer 12 during lamination, thus creating a firm connection. To further improve the adhesion of the individual fleece layers 11, 12 and 13 to the reinforcing mesh 10, the latter can also be provided with an additional layer of hot-melt adhesive, for example EVA, 5, so that the individual layers are glued together during lamination as a result of the prevailing heat.

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Fig. 3 shows an application of the new roof underlay. The roof underlay 1 is laid on wooden beams 4 of the roof structure, so that the embossed continuous fiber fleece layer 11 on the inside of the roof rests on the wooden beams 4 and the continuous fiber fleece layer 13 on the outside of the roof is covered on the outside by roof tiles 3. Due to the watertightness of the microfiber fleece layer 12 arranged inside the roof underlay 1, increased watertightness is achieved, for example against driving rain, while at the same time moisture accumulating inside the house can escape to the outside as steam through the new roof underlay.

The fleece layer 11 on the inside of the roof made of continuous filaments protects the inner fleece layer 12 made of melt-blown microfibers from damage and, thanks to its rough surface, prevents the accumulation of condensate droplets, which would impair the water vapor permeability of the roof underlay 1 to the outside.

On the outside of the roof, the inner fleece layer 12 made of melt-blown microfibers is also covered by a fleece layer 13 made of continuous filaments and is thus protected against damage. At the same time, the fleece layer 13 provides the desired mechanical properties due to its particularly high tear resistance and abrasion resistance.

Claims (16)

G 96 Protection claims 1. Diffusion-open roof underlayment which is hydrophobic and/or has been given a hydrophobic finish, containing an at least three-layer composite of nonwoven layers based on thermoplastics, wherein at least the outer nonwoven layers are formed at least predominantly from continuous filaments and at least one inner nonwoven layer is formed at least predominantly from meltblown microfibers, wherein one or more nonwoven layers are optionally consolidated by pattern embossing, characterized in that the inner nonwoven layer (12) made of meltblown microfibers is hydrophobically finished and has a basis weight of 10 to 100 g/m ² , preferably 20 to 60 g/m ² _; and the surface of the inner nonwoven layer is formed by heat treatment in a film-like manner with residual pores, whereby water vapor permeability is provided. 2. Roof underlay according to claim 1, characterized in that the layers of the composite are made from polyolefins, in particular polypropylene, whereby the fleece layer (11) on the inside of the roof facing the building made of continuous filaments has a basis weight of 17 to 60 g/m and the fleece layer (13) on the outside of the roof has a basis weight of 50 to 80 g/m ² and the inner fleece layer (12) made of meltblown microfibers has a basis weight of 10 to 100 g/m ² , preferably 20 to 60 g/m ² . 3. Roofing membrane according to claim 1, characterized in that the inner fleece layer is formed from melt-blown microfibers based on polyurethane. 4. Roofing membrane according to claim 3, characterized in that the outer fleece layers (11, 13) are made of polyester continuous filaments with a basis weight of 30 to 100 g/m ² and the inner fleece layer is made of melt-blown microfibers based on polyurethane with a basis weight of 10 to 80 g/m ² . 5. Roof underlayment according to claim 3, characterized in that the outer fleece layers (11, 13) are made of polypropylene continuous filaments with a basis weight of 3 0 to 10 0 g/m and the inner fleece layer is made of melt-blown polyurethane microfibers with a basis weight of 10 to 8 0 g/m. 6. Roof underlay according to claim 2, characterized in that the fleece layer (11) on the inside of the roof has a lower surface weight than the fleece layer (13) on the outside of the roof. 7. Roofing membrane according to one of claims 1 to 6, characterized in that an additional reinforcing insert, such as a scrim, knitted fabric, woven fabric made of thermoplastic material, is provided in the interior of the composite (1), which is adjacent to one side of the inner fleece layer (12) made of melt-blown microfibers. 0 8. Roof underlay according to claim 1, characterized in that adjacent to the inner fleece layer (12) made of melt-blown microfibers, a reinforcing insert, such as a mesh fabric, knitted fabric, fabric based on polypropylene, is formed as the inner layer of the composite (1). 9. Roof underlay according to claim 4, characterized in that adjacent to the inner nonwoven layer (12) made of meltblown microfibers, a reinforcing insert, such as a scrim, knitted fabric, or woven fabric based on polyester, is formed as the inner layer of the composite (1). 10. Roofing membrane according to claim 8, characterized in that the reinforcing insert is provided with a hot melt adhesive, in particular ethylene vinyl alcohol. 11. Roof underlayment according to one of claims 1 to 10, characterized in that the fleece layer (11) made of continuous filaments on the inside of the roof is provided with an embossed pattern (14). 12. Roof underlayment according to one of claims 1 to 11, characterized in that the nonwoven layer (13) made of continuous filaments on the outside of the roof is solidified over the surface as a result of passing through a roller gap formed by smooth rollers. 13. Roofing membrane according to claim 8 or 10, characterized in that all layers of the composite are based on polypropylene, the outer nonwoven layers (11, 13) made of continuous filaments having a basis weight of 17 to 60 g/m ² and the inner layer (12) made of meltblown microfibers having a basis weight of 10 to 100 g/m ² , preferably 20 to 60 g/m ² , and the inner layer made of the reinforcing insert having a basis weight of 20 to 60 g/m ² . 14. Roof underlay according to one of claims 1 to 13, 5 characterized in that the composite has a high degree of resistance to driving rain and a high degree of water impermeability. 15. Roofing membrane according to one of claims 1 to 14, characterized in that the inner fleece layer (12) made of melt-blown microfibers is made hydrophobic by means of hydrophobizing agents based on fluorocarbons, block copolymers of a perfluoroalkyl acrylate or fluorocarbons containing trifluoromethylsilyl groups instead of perfluoroalkyl groups. 16. Roofing membrane according to one of claims 1 to 5, characterized in that it has a tear strength of at least 120 N/5 cm.