WO2012139973A2

WO2012139973A2 - Multilayer structure comprising fibres and a vinyl chloride polymer

Info

Publication number: WO2012139973A2
Application number: PCT/EP2012/056309
Authority: WO
Inventors: Claudine Bloyaert
Original assignee: Solvay Sa
Priority date: 2011-04-11
Filing date: 2012-04-05
Publication date: 2012-10-18
Also published as: WO2012139973A3

Abstract

Multilayer structure comprising at least one layer of a fibrous network which is an assembly of elementary natural fibres and at least one layer of at least one vinyl chloride polymer, use thereof for forming articles or objects, formed articles or objects obtained, in particular sheets and panels, and process for manufacturing such multilayer structure.

Description

Multilayer structure comprising fibres and

a vinyl chloride polymer

This application claims priority to French application No. 1153148 filed on 11 April 2011 and of French application No. 1160167 filed on 8 November 2011, the whole content of these applications being incorporated herein by reference for all purposes.

The present invention relates to a multilayer structure comprising fibres and a vinyl chloride polymer. It also relates to a process for manufacturing this structure itself. It further relates to the use of this structure for forming articles or objects, and also to these articles and objects themselves and sheets and panels.

In many industries (automotive, structural engineering, shipbuilding, etc.), the aim is to optimize the mechanical properties/weight ratio of the structures used. Many methods have been developed in order to achieve this objective and one of them consists in using a multilayer structure in which a strengthening

(reinforcement) layer made of a textile material is sandwiched between two sheets known as facings (see, for example, document WO 2006/033101). By combining this technique with the choice of a lightweight material (a polymer rather than a metal), particularly lightweight structures may be obtained.

As regards the very nature of the reinforcement, "long" fibrous

reinforcements (i.e. the fibres of which have an average length of the order of 1 cm) are renowned for conferring a more pronounced improvement in the tensile behaviour (modulus and strength measured on sheets of equal thicknesses) than "short" fibrous reinforcements (length of the order of 1 mm), and also an increase in the thermal resistance, better dimensional stability and better impact strength. However, with polyvinyl chloride (PVC), which is a polymer that does not melt but can be gelled (i.e. change from a heterogeneous phase to a homogeneous phase (free of grain structure) under the action of heat), the use of such "long" reinforcements is difficult and the length of these reinforcements is in any case substantially reduced at the end of this operation. Considering the many advantages of PVC (rot-proof, resistant to UV rays, unalterable, robust, self- extinguishing, thermal-insulating and sound-insulating material, completely recyclable and particularly easy to process), it would nevertheless be advantageous to be able to use this polymer to produce multilayer structures comprising one or more layers of fibrous reinforcement.

An example of such fibrous reinforcement is described in US 3928684 which discloses articles being laminates comprising alternating layers of PVC and of coated glass fibres. However, the tensile behaviour reached with such reinforcement with glass fibres can still be improved.

The present invention aims to make it possible to use a vinyl chloride polymer in the manufacture of fibre-reinforced multilayer structures that are easy to process via the conventional methods known for processing PVC and which are characterized by a still more pronounced improvement in the tensile behaviour.

For this purpose, the main subject of the invention is a multilayer structure comprising at least one layer of a fibrous network which is an assembly of elementary natural fibres and at least one layer of at least one vinyl chloride polymer.

The expression "multilayer structure" is understood in the present description to mean a three-dimensional structure constituted of the stack of at least two layers (also referred to as films, foils or sheets), one being a layer of a fibrous network which is an assembly of elementary natural fibres, and the other a layer of at least one vinyl chloride polymer. In the case where the multilayer structure comprises more than two layers, it advantageously comprises, in alternation, a layer of a fibrous network as defined above and a layer of at least one vinyl chloride polymer.

The maximum number of layers that the multilayer structure may comprise is not critical. Advantageously, this structure may comprise up to 50 layers, preferably up to 30 layers, more particularly up to 20 layers, and very particularly up to 15 layers, comprising (in alternation when there are more than two layers) a layer of a fibrous network as defined above and a layer of at least one vinyl chloride polymer.

Advantageously, the multilayer structure therefore comprises between 2 and 50, preferably between 2 and 30, more particularly between 2 and 20 and very particularly between 2 and 15 layers.

The maximum number of layers that the multilayer structure may comprise depends on the process chosen for manufacturing said structure, which process constitutes another aspect of the present invention and which will be described further on. The total thickness of the multilayer structure depends on the number of layers that constitute it. The multilayer structure according to the invention may be constituted of layers of similar or different thicknesses. The thickness of each of the various layers may advantageously vary between 50 and 1000 μπι, preferably between 60 and 700 μιη. The total thickness of the multilayer structure is advantageously between 0.25 and 15 mm, preferably between 0.5 and 5 mm.

The multilayer structure according to the invention may be rigid or flexible.

Advantageously, the multilayer structure according to the invention contains between 10% and 80% by weight of fibrous network as defined above relative to its total weight. Preferably, this fibrous network content is between 12% and 75% by weight relative to the total weight of the multilayer structure.

The multilayer structure according to the invention comprises at least one layer of a fibrous network (which may also be referred to as a "filamentous network") which is an assembly of elementary (also referred to as "unitary") natural fibres (also referred to as "filaments").

The expression "natural fibres" is understood to define, in the present description, fibres derived from natural products, of plant or animal origin, such as hemp, flax, cotton, wood and silk for example.

Preferably, the fibrous network is an assembly of elementary flax fibres. Preferably, the fibrous network is a woven fabric of elementary, natural preferably flax, fibres (i.e. an assembly where the elementary, natural preferably flax, fibres are arranged, for one part, in the length direction and, for the other part, in the width direction) or a nonwoven fabric (also referred to as a "mat") of elementary, natural preferably flax, fibres (i.e. an assembly where the elementary, natural preferably flax, fibres are arranged randomly in one main plane). Particularly preferably, the fibrous network is a woven fabric of elementary, natural preferably flax, fibres.

The assembly of the elementary, natural preferably flax, fibres in the fibrous network may or may not be ordered and may or may not be regular. The elementary, natural preferably flax, fibres may be arranged in the fibrous network:

- in a disordered manner and may be entangled, as in the case of nonwoven fabrics or "mats", or

- in an ordered manner and may be entangled, as in the case of woven fabrics.

The elementary, natural preferably flax, fibres of the fibrous network are advantageously filiform and unitary elements. Their diameter is advantageously between 5 and 1000 μηι, preferably between 10 and 500 μιη; their length is advantageously between 1 cm and several metres.

The elementary, natural preferably flax, fibres that can be used according to the invention may have been coated with a coupling agent during their manufacturing cycle, thus improving their adhesion with the vinyl chloride polymer present in the adjacent layer or layers of the multilayer structure. Among the coupling agents customarily used, mention may be made, non-exhaustively, of silanes, polyesters, acrylic or methacrylic polymers, waxes and epoxides. Among these, silanes are preferred.

The elementary, natural preferably flax, fibres that can be used according to the invention may also have been coated or impregnated with a polymer having a nature advantageously similar to that present in the adjacent layer or layers of the multilayer structure. This coating or impregnation may be carried out by any method known to those skilled in the art (see, for example, document

EP 1 678 372 which describes the impregnation of a fibrous network by powders based on organic polymers using an electrostatic field).

The multilayer structure according to the invention comprises at least one layer of at least one vinyl chloride polymer. This layer itself may also be constituted of one or more sublayers of at least one vinyl chloride polymer. In the present description, the expression "vinyl chloride polymer" or more briefly,

"polymer" is understood to mean all polymers containing at least around 50% by weight, preferably at least 60%>, particularly preferably at least 70% by weight and very particularly preferably at least 85%> by weight of monomer units derived from vinyl chloride, therefore both vinyl chloride homopolymers (containing 100% by weight of monomer units derived from vinyl chloride) and copolymers of vinyl chloride with vinyl esters such as vinyl acetate. Among all the vinyl chloride polymers mentioned above, preference is accorded to vinyl chloride

homopolymers and to copolymers of vinyl chloride with vinyl acetate, with a particular preference to vinyl chloride homopolymers. The vinyl chloride polymer is therefore preferably a vinyl chloride homopolymer.

Use is advantageously made, within the context of the invention, of vinyl chloride polymers, preferably vinyl chloride homopolymers, having a melt flow index or K-value (conventionally known as Kw or K-wert), measured according to the standard ISO 1628 - 2, of greater than 50, preferably greater than 55. This K- value is advantageously less than 85, preferably less than 80. In the present description, the expression "at least one vinyl chloride polymer" means that the multilayer structure according to the invention may comprise a single polymer or several polymers of vinyl chloride. The term

"polymer" is used indiscriminately in the singular and in the plural in the present description.

In the case where the multilayer structure may comprise at least one layer of several polymers of vinyl chloride, these may then be mixtures of homopolymers having different melt flow indexes, mixtures of homopolymers and of copolymers or else mixtures of copolymers having different monomer compositions with one another. Preferably, the multilayer structure according to the invention comprises at least one layer of a single vinyl chloride polymer that is particularly preferably a vinyl chloride homopolymer.

The vinyl chloride polymer present in at least one of the layers of the multilayer structure according to the invention is advantageously prepared by a polymerization process carried out in an aqueous medium.

The expression "polymerization process carried out in an aqueous medium" is understood to mean, in the present description, any polymerization carried out in aqueous dispersion, i.e. either a polymerization carried out in aqueous suspension or a polymerization carried out in aqueous emulsion or else a polymerization carried out in aqueous microsuspension. These polymerizations in aqueous dispersion are advantageously performed in accordance with a radical mechanism.

The expression "polymerization in aqueous suspension" is understood to mean any polymerization process performed with stirring in an aqueous medium in the presence of dispersants and oil-soluble radical initiators.

The expression "polymerization in aqueous emulsion" is understood to mean any polymerization process performed with stirring in an aqueous medium in the presence of emulsifiers and water-soluble radical initiators.

The expression "polymerization in aqueous microsuspension", also called polymerization in (partially or completely) homogenized aqueous dispersion, is understood to mean any polymerization process in which oil-soluble initiators are used and an emulsion of monomer droplets is prepared by virtue of a powerful mechanical stirring and the presence of emulsifiers.

The preparation of the vinyl chloride polymer present in at least one of the layers of the multilayer structure according to the invention is preferably carried out in aqueous suspension. The vinyl chloride polymer present in at least one of the layers of the multilayer structure according to the invention may advantageously also contain at least one plasticizer such as a dialkyl phthalate or an alkyl adipate, and, optionally, other conventional additives, such as stabilizers, lubricants, anti-foaming agents, anti-scaling agents, thickeners, pigments, dyes, etc.

The weight of fibers in the multilayer structure represents advantageously between 30 % and 75 % of the total weight of the multilayer structure.

In another aspect, the present invention also relates to a process for the manufacture of a multilayer structure according to the invention.

The constituent layers of the multilayer structure may be assembled according to any method known for this purpose.

It is possible, for example, to press them together (optionally using an adhesive that is compatible with the nature of the fibres of the fibrous network and with the vinyl chloride polymer.)

Thus, according to a first preferred embodiment, the process according to the invention is a process for manufacturing a multilayer structure comprising at least one layer of a fibrous network and at least one layer of at least one vinyl chloride polymer according to the invention by pressing the layers between room temperature and a temperature above the glass transition temperature of the polymer and below the decomposition temperature of the fibres of the fibrous network and at a pressure between 0.1 and 15 GPa.

Preferably, the pressing operation is carried out between 85°C and 220°C, more particularly between 110°C and 195°C. Advantageously, the pressing operation is carried out at a pressure between 2.5 and 10 GPa.

This first preferred embodiment makes it possible to manufacture a multilayer structure comprising at least one layer of a fibrous network and at least one layer of at least one vinyl chloride polymer according to the invention and advantageously up to 50 layers, preferably up to 30 layers, more particularly up to 20 layers, and very particularly up to 15 layers comprising (in alternation when there are more than two layers) a layer of a fibrous network and a layer of at least one vinyl chloride polymer.

According to a variant of the first preferred embodiment of the process for manufacturing the multilayer structure according to the invention by pressing, the layer of the fibrous network is advantageously first immersed in a latex of a vinyl chloride polymer, the vinyl chloride polymer advantageously corresponding to the characteristics defined above for the vinyl chloride polymer of the layer of at least one vinyl chloride polymer. This latex is advantageously in the form of an aqueous dispersion resulting from a polymerization of the vinyl chloride preferably carried out in aqueous emulsion. This immersion is advantageously carried out at a temperature between 0°C and the glass transition temperature of the polymer, preferably between 15°C and 40°C. This immersion is advantageously carried out at atmospheric pressure.

The manufacture of the multilayer structure according to this variant may advantageously comprise drying of the fibrous network layer. This drying is preferably carried out in an oven or by hot-air blowing. The drying temperature is advantageously below the decomposition temperatures of the latex and of the fibrous network. This temperature is preferably below 160°C, more particularly below 150°C. Preferably, this latex drying temperature is above 70°C, more particularly above 80°C.

After immersion and advantageously drying, the fibrous network layer thus obtained is then preferably subjected to a pressing operation under the conditions described above in order to produce the multilayer structure.

The step of immersing a layer of a fibrous network in a vinyl chloride polymer latex and the pressing step may be repeated as a function of the number of layers desired for the multilayer structure to be manufactured.

The manufacture of the multilayer structure according to this variant may also comprise, optionally, a second pressing operation advantageously carried out between 85°C and 220°C, more particularly between 150°C and 200°C.

Advantageously, the pressing operation is carried out at a pressure between 1 and 20 GPa, preferably between 5 and 15 GPa.

According to another variant of the first preferred embodiment of the process for manufacturing the multilayer structure according to the invention by pressing, a powder of the polymer (and also of optional additives) intended for the layer(s) that contain(s) it, is advantageously spread (dispersed), in any suitable device, such as a mould for example, over one or both faces of each layer of the fibrous network. After dispersing this polymer powder over the fibrous network, the assembly may be subjected to an AC electric field. This operation has the effect of advantageously distributing the powder in the fibres.

Any AC electric field can be applied as long as the powder is well distributed in the fibres. Good results have nevertheless been obtained by applying an AC electric field of at least 0.10 kV/mm and preferably of at most 20 kV/mm. The layer of the fibrous network thus obtained is then advantageously subjected to a pressing operation advantageously carried out between 85°C and 200°C, more particularly between 150°C and 200°C. Advantageously, the pressing operation is carried out at a pressure between 1 and 15 GPa, preferably between 5 and 10 GPa.

The constituent layers of the multilayer structure, which may or may not have been pressed beforehand, may also be calendered between heated rolls.

Thus, according to a second embodiment, the process according to the invention is a process for manufacturing a multilayer structure comprising at least one layer of a fibrous network and at least one layer of at least one vinyl chloride polymer according to the invention by calendering the layers, which may or may not have been pressed beforehand, between heated rolls.

This second embodiment makes it possible to manufacture a multilayer structure comprising at least one layer of a fibrous network and at least one layer of at least one vinyl chloride polymer according to the invention and

advantageously up to 10 layers, preferably up to 7 layers, comprising (in alternation when there are more than two layers) a layer of a fibrous network and a layer of at least one vinyl chloride polymer.

According to a variant of the second embodiment of the process for manufacturing the multilayer structure according to the invention by calendering, the polymer intended for the layer(s) containing it may first be hot-mixed with optional additives then formed into a flat "crepe" by gelling (i.e. changing its constituent particles from a heterogeneous phase to a homogeneous phase (free of grain structure)) under the action of heat in a suitable device, such as a roll mill for example.

The process for manufacturing the multilayer structure according to the invention may comprise a combination, in any order, of the two embodiments described above and according to any of the variants thereof. It is thus possible, for example, to independently produce two multilayer structures by calendering and then to join these together by pressing in order to obtain a multilayer structure comprising a larger number of layers.

Another aspect of the invention also relates to the use of the multilayer structure according to the invention or of the multilayer structure obtained by the process according to the invention for forming articles or objects. For this purpose, the multilayer structure may be used, alone or together with other materials, by any known method compatible with its components, such as for example calendering, thermoforming, adhesive bonding, welding, nailing, etc.

The multilayer structure according to the invention may be used to manufacture, preferably by thermoforming, sheets for interior fittings in the motor vehicle industry (door linings, boot linings, instrument panels, etc.); it may be used to manufacture, preferably by thermoforming, panels that can be used in the shipbuilding industry, in furniture, in the building industry, etc. In these applications, the multilayer structure according to the invention advantageously improves the rigidity, the impact resistance and the tensile strength of the sheets, panels and other articles formed using them. Furthermore, the elements formed from the composite structures of the invention have good fire resistance and are easily recyclable.

Another aspect of the invention relates finally to the articles or objects formed from the multilayer structure described above or from the multilayer structure obtained by the process described above. This aspect of the invention relates more particularly to the sheets and panels obtained, preferably that are thermoformed, from the multilayer structure described above or from the multilayer structure obtained by the process described above.

Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence."

The following examples are intended to illustrate the invention without however limiting the scope thereof.

Example 1

A multilayer structure according to the invention will now be illustrated with reference to the drawing accompanying the present description. This drawing consists of the appended Figure 1, schematically representing one practical embodiment of this subject of the invention.

This figure represents a transverse cross section (not to scale) of a multilayer structure A comprising 5 layers having a total thickness, after pressing, of around 1 mm which was manufactured.

The layers 1, 3 and 5 were layers of a fibrous network which was a woven fabric of elementary flax fibres (called here after "woven fabric of flax fibres") having the distinctive feature of being constituted of 4 flax fibres placed parallel to one another in each of the two directions i.e. length and width (280 g/m²). The woven fabric of flax fibres was characterized by a thickness of 0.65 mm.

The layers 2 and 4 were layers with a thickness of around 250 μπι of a rigid PVC film extruded from a composition comprising 100 parts by weight of a vinyl chloride homopolymer of K-value = 57, sold by the company SolVin under the name S257 RF, 3 parts by weight of epoxidized soybean oil, 1.5 parts by weight of an organotin-based heat stabilizer and 1.6 parts by weight of a mixture of ester lubricants sold under the names Loxiol G 15 and G 72 by the company Emery Oleochemicals.

For the manufacture of the multilayer structure (multilayer structure A), the woven fabric of flax fibres (width: 1.45 m) was cut to the size of the shaping mould. Placed in the mould, heated to 180°C, were a woven fabric of flax fibres, then a rigid PVC film, then a second layer of woven fabric, then another PVC film and finally a woven fabric, by placing the flax woven fabrics in the same direction. The weight of woven fabric of flax fibres of the layers thus stacked represented 55% of their total weight and the weight of the PVC films represented 45% of their total weight.

The mould was then closed without exerting pressure for 2 minutes. A pressure of 10 GPa was then applied for 1 minute, then the mould was cooled to 50°C. The mould was finally opened in order to extract the pressed multilayer structure.

In the same way a second multilayer structure (multilayer structure B) was manufactured, which differed from the multilayer structure A due to the fact that the weight of woven fabric of flax fibres of the layers thus stacked represented 45% of their total weight and the weight of the PVC films represented 55% of their total weight, and due to the fact that the woven fabric of flax fibres used had the distinctive feature of being constituted of 4 flax fibres placed parallel to one another in one of the two directions i.e. the length and of a single flax fibre in the other direction i.e. the width (180 g/m²). The woven fabric of flax fibres was characterized by a thickness of 0.53 mm.

Finally, in the same way, a third multilayer structure (multilayer structure C) was manufactured, which differed from the multilayer structure A due to the fact that the weight of woven fabric of flax fibres of the layers thus stacked represented 45%) of their total weight and the weight of the PVC films represented 55% of their total weight, and due to the fact that the woven fabric of flax fibres used had the distinctive feature of being constituted of 2 flax fibres placed parallel to one another in one of the two directions i.e. the length and of a single flax fibre in the other direction i.e. the width. The woven fabric of flax fibres was characterized by a thickness of 0.51 mm.

Test specimens were then cut from these structures A, B and C in order to determine the mechanical properties thereof.

The details and results of these measurements are assembled in the table below. In this table, "transverse direction" means in the width direction while "longitudinal direction" means in the length direction.

Table

* Acronym of "Heat Deflection Temperature", which is the temperature at which a polymer deforms under a specific load.

** Acronym of "Instrumented Falling Weight". Example 2

A multilayer structure D was manufactured by the same process as that described in Example 1 for the structure B except that the woven fabric of flax fibres was immersed for 5 minutes in a bath of latex having the following composition:

- 31.40% by weight of a dispersion of a vinyl chloride homopolymer having a K-value equal to 72 (polymerized in aqueous emulsion) sold by the company Solvin under the name 072 GA;

- 12.44% by weight of plasticizer (diisononyl phthalate);

- 0.65%) by weight of heat stabilizer (di(w-octyl)tin thioglycolate);

- 0.91%) by weight of an anionic emulsifier (mixture of fatty acid sodium salt and of sodium dodecylbenzenesulphonate);

- 0.50% by weight of a nonionic emulsifier sold under the name Triton X 100 by Sigma Chemical;

- 0.5%) by weight of cellulose ether;

- 53.6%) by weight of water.

It was left to drain for 10 minutes and the latex-impregnated woven fabric of flax fibres was placed in an oven at 90°C for 3 minutes to dry the latex.

The manufacture of the multilayer structure D was then continued as described in Example 1 for the structure B.

Test specimens were then cut from this structure D in order to determine the mechanical properties thereof.

The details and results of these measurements (carried out as in Example 1) are assembled below. "Transverse direction" means in the width direction while "longitudinal direction" means in the length direction.

Content of woven fabric of flax fibres (% by weight/total weight): 32

Final thickness of the multilayer structure (mm): 1.1

IFW impact (mean value in J/mm): 2.8

HDT (mean values) (°C): 73

Tensile properties (transverse direction) (mean values):

Modulus (MPa): 3271

Elongation (%): 3.29

Tensile strength (MPa): 45.5

Tensile properties (longitudinal direction) (mean values):

Modulus (MPa): 8058

Elongation (%): 2.12 Tensile strength (MPa): 99.27

Example 3

A multilayer structure E having a total thickness, after pressing, of around 4 mm, was manufactured by the same process as that described in Example 1. The multilayer structure E comprised a total of 15 layers, namely: 8 layers of rigid PVC film (including the top and bottom) alternating with 7 inner layers of the woven fabric of flax fibres that was used for the manufacture of the multilayer structure B.

The manufacture of the multilayer structure E was then continued as described in Example 1 for the structure B. Test specimens were then cut from this structure E in order to determine the mechanical properties thereof.

Content of woven fabric of flax fibres (% by weight/total weight): 72

IFW impact (mean value in J/mm): 3.935

HDT (mean values) (°C): 70

Tensile properties (longitudinal direction) (mean values):

Modulus (MPa): 13 576

Elongation (%): 1.55

Tensile strength (MPa): 138

Flexural properties (measured according to the standard ISO 178)

(longitudinal direction) (mean values):

Modulus (MPa): 8196

Elongation (%): 3.55

Tensile strength (MPa): 137.8

It was observed that the mechanical tensile properties of the multilayer structure E are around 4 times greater than those of a rigid PVC sheet of the same thickness.

Example 4 (comparative example)

Two multilayer structures F and G were manufactured by the same process as that described in Example 1 except that the woven fabrics of flax fibres were replaced by woven fabrics of glass fibres sold by Adfors St Gobain under the commercial name respectively of TwinFab^®73 and E 205.

Test specimens were then cut from these structures F and G in order to determine the mechanical properties thereof. The details and results of these measurements (carried out as in Example 1) are assembled below. "Transverse direction" means in the width direction while "longitudinal direction" means in the length direction.

Test specimens originating from structure F

Content of woven fabric of glass fibres (% by weight/total weight): 13

Final thickness of the multilayer structure (mm): 1

Tensile properties (transverse and longitudinal directions) (mean values):

Modulus (MPa): 3238

Elongation (%): 2.3

Tensile strength (MPa): 48.9

Test specimens originating from structure G

Content of woven fabric of glass fibres (% by weight/total weight): 24 Final thickness of the multilayer structure (mm): 1.2

Tensile properties (longitudinal direction) (mean values):

Modulus (MPa): 4241

Elongation (%): 3.41

Tensile strength (MPa): 131.8

It can be seen that the tensile modulus measured in longitudinal direction for multilayer structures F and G comprising layers of woven fabrics of glass fibres are lower than the ones measured in same longitudinal direction for multilayer structures according to Examples 1 to 3 comprising layers of woven fabrics of flax fibres.

Claims

C L A I M S

1 - Multilayer structure comprising at least one layer of a fibrous network which is an assembly of elementary natural fibres and at least one layer of at least one vinyl chloride polymer.

2 - Multilayer structure according to Claim 1, characterized in that the fibrous network is an assembly of elementary flax fibres.

3 - Multilayer structure according to either Claim 1 or 2, characterized in that it comprises up to 50 layers comprising (in alternation when there are more than two layers) a layer of a fibrous network and a layer of at least one vinyl chloride polymer.

4 - Multilayer structure according to any one of Claims 1 to 3,

characterized in that it comprises up to 20 layers comprising (in alternation when there are more than two layers) a layer of a fibrous network and a layer of at least one vinyl chloride polymer.

5 - Multilayer structure according to any one of Claims 1 to 4,

characterized in that it contains between 10% and 80% by weight of fibrous network relative to its total weight.

6 - Multilayer structure according to any one of Claims 1 to 5,

characterized in that the fibrous network is a woven fabric of elementary fibres or a nonwoven fabric of elementary fibres.

7 - Multilayer structure according to any one of Claims 1 to 6,

characterized in that the fibrous network is a woven fabric of elementary fibres.

8 - Multilayer structure according to any one of Claims 1 to 7,

characterized in that the vinyl chloride polymer is a vinyl chloride homopolymer.

9 - Process for manufacturing a multilayer structure comprising at least one layer of a fibrous network and at least one layer of at least one vinyl chloride polymer according to any one of Claims 1 to 8 by pressing the layers between room temperature and a temperature above the glass transition temperature of the polymer and below the decomposition temperature of the fibres of the fibrous network and at a pressure between 0.1 and 15 GPa. 10 - Process according to Claim 9, characterized in that the layer of the fibrous network is first immersed in a latex of a vinyl chloride polymer.

11 - Process for manufacturing a multilayer structure comprising at least one layer of a fibrous network and at least one layer of at least one vinyl chloride polymer according to any one of Claims 1 to 8 by calendering the layers, which may or may not have been pressed beforehand, between heated rolls.

12 - Use of the multilayer structure according to any one of Claims 1 to 8 or of the multilayer structure obtained by a process according to any one of Claims 9 to 11 for forming articles or objects.

13 - Articles or objects formed from the multilayer structure according to any one of Claims 1 to 8 or from the multilayer structure obtained by a process according to any one of Claims 9 to 11.

14 - Sheets and panels obtained from the multilayer structure according to any one of Claims 1 to 8 or from the multilayer structure obtained by a process according to any one of Claims 9 to 11.