Multi-layer structure for the creation of a reinforced and recyclable floor covering

Abstract

The invention relates to a multi-layer structure (1) for producing a floor covering, comprising at least one surface layer (2) bonded to a backing layer (3b), the surface layer (2) and the backing layer (3b) being made from PVC, the multi-layer structure (1) comprising successively and from top to bottom, between the surface layer (2) and the backing layer (3b), a first woven reinforcement (5a), an intermediate layer (3a), a second woven reinforcement (5b), bonded together, to the surface layer (2) and to the backing layer (3b) by means of bonding layers (6) in the form of hot-melt films, for example made of copolyamide or copolyester, or of layers of crosslinked polyurethane adhesive, the multi-layer structure (1) comprising a surface mass of between 2000 and 3000 g / m²,the intermediate layer (3a) and the backing layer (3b) are made from PVC and each comprise:- a thickness of between 100 µm and 200 µm;- between 5 and 25 PCR of plasticizer, preferably between 6 and 15 PCR of plasticizer. Figure for the abstract: Fig. 3,

Description

Title of the invention: Multi-layer structure for the production of a reinforced and recyclable floor covering Technical field

[0001] The invention relates to the technical field of flexible floor coverings, preferably presented in rolls or in the form of a welded and adhesive kit.

[0002] The invention relates to a multi-layer structure for producing a reinforced and recyclable floor covering.

[0003] The invention finds an advantageous application for covering honeycomb aircraft floor panels, for example. Prior art

[0004] A multi-layer structure for producing a floor covering is well known in the prior art, comprising a surface layer bonded to a so-called "laminated" backing layer used to cover aircraft floors, for example.

[0005] In this type of structure, the laminated backing layer consists of a woven reinforcement of glass fibers impregnated with phenolic or polyester resins. This backing layer ensures that the floor covering is held on its support, provides dimensional stability, blocks the migration of plasticizers from the PVC surface layers, improves the impact resistance of the floor covering and reduces the phenomenon of "telegraphing", which results in the transmission of irregularities in the support to the floor covering. Another important aspect of a floor covering used to cover aircraft floors is its ability to resist deformations of the floor in flight which can cause creases, also called "buckling".

[0006] The laminated backing layer is complex to manufacture and requires a certain technical mastery, for which a limited number of companies have the skills, which implies a high production cost.

[0007] Another disadvantage of this laminated backing layer is that it is not recyclable due to the use of phenolic resin. To date, this type of layer is mostly crushed and discarded.

[0008] Documents US2010 / 0227132 and EP3064347 are known which describe multi-layer structures for producing floor coverings in which a backing layer is composed of a composite material comprising woven or non-woven reinforcing fibers and a thermosetting or thermoplastic polymer resin, chosen from the group comprising polyester resin; phenolic resin; epoxy resin; polysulfone; vinylester resin; epoxy-acrylic resin; and their mixtures.

[0009] The resulting disadvantage is that the use of a thermosetting resin affects the recyclability of the floor covering.

[0010] Replacing the phenolic resin with a thermoplastic resin can also affect recyclability, because the structure becomes too heterogeneous. In addition, the expected performances of the multilayer structure are not achieved, such as weldability between two structures or resistance to traffic for example. Statement of the invention

[0011] One of the aims of the invention is therefore to overcome the drawbacks of the prior art by proposing a multi-layer structure, for example used to cover aircraft floors, having a backing layer whose manufacturing cost is low compared to that of laminated layers, and to provide a multi-layer structure giving complete satisfaction in terms of the hold of the covering on its support, dimensional stability, and impact resistance of the floor covering.

[0012] Another objective of the invention is to provide such a multilayer structure whose recyclability is improved and whose weight is limited.

[0013] Another objective of the invention is to provide such a multilayer structure whose resistance to telegraphing and to buckling are comparable or even better than existing solutions.

[0014] For this purpose, a multi-layer structure has been developed for producing a floor covering, comprising at least one surface layer bonded to a backing layer, the surface layer and the backing layer being made from PVC.

[0015] According to the invention, the multilayer structure comprises successively and from top to bottom, between the surface layer and the backing layer, a first woven reinforcement, an intermediate layer and a second woven reinforcement, bonded together, to the surface layer and to the backing layer by means of bonding layers in the form of hot-melt films, for example made of copolyamide or copolyester, or of layers of crosslinked polyurethane glue, the multilayer structure comprises a surface mass of between 2000 and 3000 g / m2, and the intermediate layer and the backing layer are made from PVC and each comprise: - a thickness between 100 pm and 200 pm; - between 5 and 25 PCR of plasticizer, preferably between 6 and 15 PCR of plasticizers.

[0016] The woven reinforcements improve the rigidity and dimensional stability of the multi-layer structure.

[0017] The amount of plasticizer is directly related to the amount of flame retardant needed in the composition since plasticizers are flammable compounds. Limit thus the quantity of plasticizer between 5 and 25 PCR, makes it possible to limit the quantity of flame retardant or even not to integrate it into the composition, to limit the migration of plasticizers in the double-sided adhesives generally used to bond the multi-layer structure to a honeycomb floor of an aircraft for example, and consequently makes it possible to avoid degrading the adhesion properties of these adhesives over time. A quantity of plasticizers in the intermediate and backing layers between 6 and 15 PCR makes it possible to obtain a better compromise between the rigidity of the structure, its weight and its maneuverability to facilitate its installation.

[0018] The multi-layer structure according to the invention thus has an intermediate and backing layer, making it possible to obtain a floor covering whose manufacturing cost is relatively low, and which gives complete satisfaction in terms of the holding of the covering on its support, dimensional stability, heat curvature and impact resistance. Given that the surface layer, the intermediate layer and the backing layer are all made from PVC, the recyclability of the multi-layer structure becomes conceivable.

[0019] Preferably, the backing layer and / or the intermediate layer are made from PVC and have a flexural strength, measured according to the ISO 2493-2 standard, of between 0.3 mN.m and 1.5 mN.m in order to limit telegraphing effects and provide sufficient rigidity to the structure.

[0020] According to a particular embodiment, the surface layer comprises an upper layer, in particular a wear layer, and one or more intermediate layers of plasticized PVC.

[0021] For example, the upper layer is transparent, and a first interlayer is directly arranged under the surface layer and is for example in the form of a film printed with a decoration. In the latter case, a second, non-transparent interlayer is preferably arranged under the printed film to ensure sufficient opacity.

[0022] The surface, interlayer, intermediate and backing layers are preferably produced by calendering, pressing, coating or extrusion so as to form a relatively smooth layer whose composition is homogeneous throughout the thickness.

[0023] According to a particular embodiment, the first and / or the second woven reinforcement may be impregnated with a thermoplastic or thermosetting polymer in an amount of between 1% and 10% by weight of each impregnated woven reinforcement so as not to degrade the recyclability. This allows the multilayer structure to have greater rigidity. The thermoplastic or thermosetting polymer may be chosen from the group comprising polyurethane resin, polyester resin, phenolic resin, epoxy resin, polysulfone, vinylester resin, epoxy-acrylic resin, and mixtures thereof.

[0024] Preferably and to improve the resistance to the phenomenon known to those skilled in the art under the English term "telegraphing", a foamed layer, preferably made from PVC, is bonded to a lower face of the backing layer by means of a bonding layer in the form of hot-melt films, a layer of crosslinked polyurethane (PUR), a layer of thermoplastic copolyester (CoPES), copolyamide or thermoplastic polyurethane (TPU).

[0025] This foamed layer advantageously has a density of between 0.15 and 0.25, preferably between 0.20 and 0.25, and a thickness of between 1.5 and 3 mm, preferably between 1.9 and 2.5 mm, in order to provide good resistance to telegraphing without however reducing the resistance to indentation of the multi-layer structure.

[0026] Advantageously, this foamed layer comprises a third reinforcing reinforcement impregnated at least in part in its thickness so as to improve the strength of the foamed layer and of the entire multilayer structure. The third reinforcing reinforcement at least in part impregnated in the thickness of the foamed layer may be a layer of non-woven textile, preferably a veil of glass or polyester fibers, a reinforcing grid, preferably a grid of glass or polyester fibers, or even a complex comprising a layer of non-woven textile bonded to a reinforcing grid.

[0027] Advantageously, and to facilitate the installation of the multilayer structure according to the invention, the multilayer structure comprises on a lower face intended to be opposite the ground, that is to say directly on the lower face of the backing layer, a layer of repositionable adhesive, that is to say which has a power of adhesion to the multilayer structure greater than the power of adhesion to the ground in order to be able to detach and reposition the multilayer structure. Brief description of the drawings

[0028] [Fig.l] illustrates in section a multi-layer structure according to a first embodiment of the invention, with a top layer, an interlayer, a first woven reinforcement, an intermediate layer, a second woven reinforcement and a backing layer.

[0029] [Fig.2] is a view similar to that of [Fig.l], with two interlayers.

[0030] [Fig.3] is a view similar to that of [Fig.l], with the addition of a foamed layer on the lower face of the backing layer comprising a third reinforcing reinforcement impregnated at least partly in its thickness.

[0031] [Fig.4] is a view similar to that of [Fig.l], with the addition of a foamed layer on the underside of the backing layer and a repositionable adhesive facing the floor. Detailed description of the invention

[0032] With reference to Figures 1 to 4, the invention relates to a multilayer structure (1) for producing a floor covering, preferably for covering aircraft floors, for example honeycomb floors, without this being limiting.

[0033] The multilayer structure (1) according to the invention has a low manufacturing cost, while possessing optimal performance, that is to say in terms of the hold of the covering on its support, dimensional stability, impact resistance of the floor covering, recyclability.

[0034] For this purpose, the multilayer structure (1) according to the invention comprises at least one surface layer (2) made from PVC, bonded to a backing layer (3b), also made from PVC.

[0035] According to the invention, the multilayer structure (1) comprises a surface mass of between 2000 and 3000 g / m2, preferably between 2100 and 2600 g / m2, and successively and from top to bottom, between the surface layer (2) and the backing layer (3b), a first woven reinforcement (5a), an intermediate layer (3a), a second woven reinforcement (5b), bonded together, to the surface layer (2) and to the backing layer (3b) by means of bonding layers (6) in the form of hot-melt films, for example made of copolyamide, thermoplastic polyurethane, or copolyester, or of layers of crosslinked polyurethane glue.

[0036] The intermediate layer (3a) and the backing layer (3b) are each made from PVC and comprise: - a thickness between 100 pm and 200 pm; - between 5 and 25 PCR of plasticizer, preferably between 6 and 15 PCR of plasticizers, “PCR” meaning part(s) percent of resin, the term “resin” relating to the PVC of the intermediate layer (3a) and backing (3b); - preferably a flexural strength, in particular the flexural strength B of PVC films measured according to ISO 2493-2 standard on a “Taber Stiffness” test bench from the company “Taber Industries”, model “TABER 150-E”, between 0.30 mN.m and 1.5 mN.m.

[0037] A bonding layer (6) generally has a thickness of between 10 and 100 μm, preferably between 10 and 50 μm.

[0038] Each intermediate and / or backing layer may not contain fillers or may optionally comprise a quantity of fillers of between 1 and 50 PCR. The fillers may be chosen from the group comprising calcium carbonate, chalks, kaolin, talc, silica. Each intermediate and / or backing layer may further contain at least one additive chosen from the following group: thermal stabilizers, desiccants, lubricants, processing aids "), pigments, flame retardants.

[0039] A limited quantity of plasticizer makes it possible to limit the migration of plasticizers in the double-sided adhesives which are generally used to bond the multi-layer structure (1) to a floor, so as to avoid degrading the adhesion properties of said adhesives over time.

[0040] The bending strength is tested in the machine direction, the bending strength is determined as the average bending moment of 10 measured values, namely 5 bending movements in one direction and 5 bending movements in an opposite direction.

[0041] The multilayer structure (1) obtained thus has a low weight making it possible to limit its impact on the fuel consumption of a vehicle carrying it, while meeting the mechanical constraints of this type of application, in particular in terms of resistance to telegraphing and buckling.

[0042] The surface layer (2) may comprise an upper layer (2a), in particular a wear layer, and one, see [Fig.l], or several, see [Fig.2], intermediate layers (4) made of plasticized PVC, for example with a quantity of plasticizer greater than 15 PCR, preferably less than 40 PCR. Each intermediate layer may not contain fillers or may optionally comprise a quantity of fillers of between 1 and 150 PCR. The fillers may be chosen from the group comprising calcium carbonate, chalks, kaolin, talc, silica. Each intermediate layer may further contain at least one additive chosen from the following group: thermal stabilizers, desiccants, lubricants, processing aids, pigments, flame retardants.

[0043] The upper layer (2a) and the intermediate layers (4) are made integral for example by lamination, i.e. by hot lamination. For example, the upper layer (2a) preferably has a thickness of between 0.35 mm and 0.55 mm, and the intermediate layer(s) (4) each preferably has a thickness of between 0.15 mm and 0.60 mm.

[0044] The upper layer (2a) is plasticized and optionally filled, and may optionally have a surface varnish well known to those skilled in the art, to ensure ease of maintenance. It may further contain at least one additive chosen from the following group: UV thermal stabilizers, desiccants, lubricants, processing aids, pigments, flame retardants.

[0045] According to a particular embodiment, the upper layer (2a) is transparent to light in the range visible to the human eye and the interlayer (4), directly arranged under the upper layer (2a), may be in the form, for example, of a film printed with a decoration on its face opposite the upper layer (2a). In the latter case, it is preferable to arrange a second layer in interlayer (4), non-transparent, which is positioned under the printed film to ensure sufficient opacity to the decoration and to avoid seeing the structure of the first woven reinforcement (5a). Alternatively, a decoration can be directly printed on the reverse side of the upper layer, facing the interlayer (4).

[0046] The first and second woven reinforcements (5a, 5b) make it possible to improve the rigidity and dimensional stability of the multilayer structure (1), and are for example in the form of a glass fabric.

[0047] Due to the lack of affinity of the woven reinforcements (5a, 5b) with PVC, said woven reinforcements (5a, 5b) are bonded to the surface layer (2), to the intermediate layer (3a) and to the backing layer (3b) by means of bonding layers (6), for example in the form of hot-melt films (for example, made of copolyamide CoPA, thermoplastic polyurethane TPU, or thermoplastic copolyester or CoPES), of layers of crosslinked polyurethane PUR, applied in the form of glue well known to those skilled in the art according to the English designation "hotmelt".

[0048] The first and / or second reinforcements (5a, 5b) are preferably woven in a plain weave, without this being limiting. A twill or satin woven weave could quite easily be envisaged.

[0049] The first and / or second woven reinforcements (5a, 5b) are preferably made from glass fibers, polyamide fibers or polyester fibers.

[0050] The glass fibers may have a count of between 22 Tex and 68 Tex. The polyester fibers may have a count of around 1100 decitex. The polyamide fibers may have a count of between 44 decitex and 78 decitex. The first and / or second woven reinforcements (5a, 5b) generally have a thickness of between 150 μm and 300 μm, preferably between 165 μm and 205 μm. The first and / or second woven reinforcements (5a, 5b) generally have a surface mass of between 150 and 300 g / m2, although this value depends on the nature of the fibers used.

[0051] When the first and / or second woven reinforcement (5a, 5b) is made from glass fiber, it has a number of warp threads of between 17 and 18 threads per cm and a number of weft threads of between 13.5 and 14 threads per cm.

[0052] Below 17 warp threads per cm or 13.5 weft threads per cm, the first and / or second woven reinforcement (5a, 5b) becomes porous, in particular with a count between 22 and 68 Tex.

[0053] Preferably, the first and / or the second woven reinforcement (5a, 5b) is impregnated with a thermoplastic or thermosetting polymer in an amount of between 1% and 10% by weight of the impregnated woven reinforcement so as not to degrade the recyclability, to obtain greater rigidity and to limit or even eliminate the passage of glue likely to clog the lamination line during the assembly process. layers.

[0054] The thermosetting or thermoplastic polymer used to impregnate the first and / or the second woven reinforcement may be chosen from the group comprising polyurethane resin, polyester resin, phenolic resin, epoxy resin, polysulfone, vinylester resin, epoxy-acrylic resin, and mixtures thereof.

[0055] Preferably and with reference to figures 3 and 4, and to improve the resistance to the phenomena known to those skilled in the art under the English terms "telegraphing" and "buckling" also called "waving", a foamed layer (7) is bonded to a lower face of the backing layer (3) by means of a bonding layer (6) in the form of "hotmelt" glue, for example in polyurethane PUR or copolyester "CoPES".

[0056] The foamed layer (7) advantageously has a density of between 0.15 and 0.25, preferably between 0.20 and 0.25 and a thickness of between 1.5 and 3 mm, preferably between 1.9 and 2.5 mm, in order to improve the resistance to “telegraphing” and “buckling” (or “waving”).

[0057] Preferably and with reference to [Fig. 3], the foamed layer (7) comprises a third reinforcing reinforcement (9) impregnated at least partly in its thickness so as to improve the strength of the foamed layer (7) and of the entire multilayer structure. The third reinforcing reinforcement (9) may be a layer of non-woven textile, preferably a veil of glass, cellulose or polyester fibers alone or in a mixture, a reinforcing grid, preferably a grid of glass or polyester fibers, or even a complex comprising a layer of non-woven textile bonded to a reinforcing grid. The layer of non-woven textile of the third reinforcing reinforcement (9) generally has a weight of between 20 and 80 g / m2. The grid of the third reinforcing reinforcement (9) generally has a texture greater than 2 x 2 and a count of weft and warp threads of between 34 and 68 tex.The third reinforcing frame optionally comprises a binder such as PVAc (polyvinyl acetate). The foamed layer may in particular be obtained from a PVC plastisol coated on the third reinforcing frame (9) then gelled so as to impregnate at least partially in its thickness said frame. Preferably, the third reinforcing frame (9) is positioned opposite the backing layer (3b) and is bonded to said backing layer (3b) by a bonding layer (6).

[0058] Preferably and with reference to [Fig.4], the multilayer structure (1) comprises on a lower face intended to be in contact with the ground, that is to say for example directly the lower face of the backing layer (3), or the lower face of the non-woven textile layer, a repositionable double-sided adhesive (8), that is to say which adheres more to the multilayer structure (1) than to the ground on which it is placed, thus facilitating installation.

[0059] The Applicant carried out tests on a product A in accordance with the invention; Product A, with a surface mass of 2150 g / m2, includes: - a top layer (2a) made of 0.50 mm thick PVC, 640 g / m2; - an interlayer (4) of 0.50 mm thick PVC, 640 g / m2; - a bonding layer (6) in the form of a hot-melt film with a thickness of 0.045 mm, of 50 g / m2; - a first woven reinforcement (5a) impregnated with a thickness of 0.15mm and 223g / m2; - a bonding layer (6) in the form of a layer of crosslinked polyurethane glue of 35g / m2 - an intermediate layer (3a) of plasticized PVC of 8 PCR and 140 pm, with a flexural strength measured according to ISO 2493-2 of 0.35 mN.m. - a bonding layer (6) in the form of a layer of crosslinked polyurethane glue of 35g / m2 - a second woven reinforcement (5b) impregnated with a thickness of 0.15mm and 223g / m2; - a bonding layer (6) in the form of a layer of crosslinked polyurethane glue of 35g / m2 - a backing layer (3b) in plasticized PVC of 8 PCR and 140 pm, with a flexural strength measured according to ISO 2493-2 of 0.35 mN.m.

[0060] [Tables 1] Characteristics Standards Requirements Results Mass per unit area ISO 2286-2 2100+ / -150 g / m2 2150 g / m2 Thickness ISO 2286-3 < 3.7 mm 1.75 mm Compression strength - longitudinal direction (L) ISO 604 >80 N 110 N Compression strength - transverse direction (T) ISO 604 >80 N 90 N Efh3 ("bending moment) - longitudinal direction (L) ISO 178 > 1500 N.mm 1970 N.mm Efh3 ("bending moment) - transverse direction (T) ISO 178 > 1500 N.mm 1540 N.mm Vertical flammability test 12s FAR 25.853 compliant YES Peel strength (between reinforcement layers) ISO 4578 >12 N / 25mm 110 N / 25 mm Recyclability YES Dimensional stability (70°C for 168h) ISO 23999 + / - 0.2% 0.05% Heat curvature (70°C for 168h) ISO 23999 < 10 mm 1 mm Peel strength between the back (3b) of the product and a double-sided adhesive sold by 3M under the reference 3M950 ISO 4578 > 20 N / 25mm 30 N / 25 mm

[0061] In this table 1 we see that product A meets all the requirements in terms of surface mass, thickness, compression force and bending moment, flammability and peel strength. On the other hand, recyclability is improved compared to existing solutions. The characteristics of dimensional stability, curvature and holding on the support (peel strength) are also satisfactory.

[0062] A second series of tests is carried out on a product B. Product B conforms to the invention and has the characteristics and different layers of product A in adding a foamed layer (7) bonded to the backing layer (3b) via a bonding layer (6) in the form of a 35g / m2 crosslinked polyurethane glue layer, according to [Fig.4]. The foamed layer (7) comprises a third reinforcing reinforcement (9) 150 μm thick partially impregnated in its thickness and in the form of a complex comprising a layer of non-woven textile made of cellulose and polyester fiber weighing 20g / m2 bonded to a glass yarn reinforcing grid by a PVAc binder, the grid having a texture of 5 x 3 and a count of the weft and warp threads of 34 tex by 34tex. The foamed layer is obtained from a PVC plastisol coated on the third reinforcing reinforcement (9) then gelled so as to impregnate at least partly in its thickness said reinforcement. Different types of foamed layers (7) are tested by varying their densities, surface masses and thicknesses.The telegraphing resistance test consists of visually observing the appearance of a support defect on the surface of the multilayer structure (1). The results are classified between: no apparent defect (+++), apparent but acceptable defect (++), apparent and unacceptable defect (+). The buckling resistance test consists of visually observing the appearance of a bump on the surface of the multilayer structure (1). The results are classified between: no apparent bump (+++), apparent but acceptable bump (++), apparent unacceptable bump (+).

[0063] [Tables2] Foamed layer (7) Telegraphing Buckling Punching (NF EN ISO 24343-1) Density mass per unit area (g / m2) thickness (mm) 0.17 400 2.4 +++ ++ 0.7 mm 0.17 350 2 ++ ++ 0.5 mm 0.23 400 1.75 + ++ 0.2 mm 0.23 450 1.95 ++ ++ 0.2 mm 0.23 500 2.2 ++ ++ 0.3 mm

[0064] In this table 2, we note that a foamed layer (7) with a density between 0.20 and 0.35 and a thickness between 1.9 and 2.5 makes it possible to obtain a better compromise between the punching resistance of the multilayer structure (1) and its resistance to telegraphing and buckling. This solution is therefore preferable.

Claims

Claims

1. Multi-layer structure (1) for producing a floor covering, comprising at least one surface layer (2) bonded to a backing layer (3b), the surface layer (2) and the backing layer (3b) being made from PVC; characterized in that the multi-layer structure (1) comprises successively and from top to bottom, between the surface layer (2) and the backing layer (3b), a first woven reinforcement (5a), an intermediate layer (3a), a second woven reinforcement (5b), bonded together, to the surface layer (2) and to the backing layer (3b) by means of bonding layers (6) in the form of hot-melt films, for example made of copolyamide or copolyester, or layers of crosslinked polyurethane adhesive;and in that the multi-layer structure (1) comprises a surface mass of between 2000 and 3000 g / m2, and in that the intermediate layer (3a) and the backing layer (3b) are made from PVC and each comprise: - a thickness of between 100 pm and 200 pm; - between 5 and 25 PCR of plasticizer, preferably between 6 and 15 PCR of plasticizer.;

2. Multilayer structure (1) according to claim 1, characterized in that the intermediate layer (3a) and / or the backing layer (3b) comprise a flexural strength measured according to ISO 2493-2 of between 0.30 mN.m and 1.5 mN.m.

3. Multilayer structure (1) according to one of the preceding claims, characterized in that the surface layer (2) comprises an upper layer (2a) and one or more intermediate layers (4) made of plasticized PVC.

4. Multilayer structure (1) according to claim 3, characterized in that the upper layer (2a) is transparent and the intermediate layer (4) which is directly arranged under the upper layer (2a) is a film printed with a decoration.

5. Multilayer structure (1) according to one of the preceding claims, characterized in that the first woven reinforcement (5a) and / or the second woven reinforcement (5b) are impregnated with a thermoplastic or thermosetting polymer in an amount of between 1% and 10% by weight of the impregnated woven reinforcement.

6. Multilayer structure (1) according to one of the preceding claims, characterized in that a foamed layer (7) preferably made from PVC is bonded to a lower face of the backing layer (3b) by means of a bonding layer (6) in the form of hot-melt films or a crosslinked polyurethane adhesive layer.

7. Multilayer structure (1) according to claim 6, characterized in that the foamed layer (7) has a density of between 0.15 and 0.25, preferably between 0.20 and 0.25 and a thickness of between 1.5 and 3 mm, preferably between 1.9 and 2.5 mm.

8. Multilayer structure (1) according to claim 6, characterized in that the foamed layer (7) comprises a third reinforcing frame (9) impregnated at least partly in its thickness.

9. Multilayer structure (1) according to one of the preceding claims, characterized in that it comprises on a lower face intended to be facing the ground, a layer of repositionable double-sided adhesive (8).

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