The present invention relates to a multilayer structure suitable for use in particular in the transport water.

TECHNICAL BACKGROUND

Fluorinated polymers, particularly polymers obtained from vinylidene fluoride, have high chemical inertness, making them especially suitable for the transport of many chemicals. Their resistance to chlorinated agents (chlorine dioxide, chloramine, sodium hypochlorite ...) actually prime candidates for water transportation applications, in particular hot water, particularly in hospitals and healthcare, where aggressive treatments based on chlorinated agents are commonly used.

The pipes or pipes of drinking water must meet strict criteria. The pipeline must not lose its mechanical properties due to the treated water it contains; in particular it must be resistant to aging, do not puncture or break and be flexible for easy installation. It must also preserve the quality of transported water: the structure of the pipe must not discharge into the water transported given a small amount of chemical compounds and / or prevent the buildup of a biofilm on the inner surface of the pipe. The pipe must also be easy to manufacture, for example by coextrusion.

Polyolefins and in particular polyethylenes exhibit mechanical properties which make them suitable for use as pipe to pipe. Nevertheless, the limited chemical resistance of these polymers makes them susceptible to chlorinated agents used for the treatment of water, especially under high temperature conditions (greater than 70 ° C). An inner layer of fluoropolymer combined with a polyolefin layer may thus protect the latter from the action of such aggressive chemicals contained in water. However, due to their different chemical nature, such polymers are incompatible, so it is difficult to adhere the fluorinated polymers on polyolefins.

DE 20201 1 103017 U1 discloses pipes for drinking water which comprises a tube PVDF (poly vinylidene fluoride). This tube is covered with aluminum foil and secured to the latter by means of a binder; the aluminum foil is itself covered of a layer of polyethylene. The aluminum foil provides the line a low permeation to gases and limits the migration of the chemical constituents of the polyethylene to the water. The presence of the aluminum foil makes the expensive piping and difficult to manufacture.

Document FR 2892171 discloses a tube that can be used as a pipeline for the transportation of water. This tube comprises a multilayer structure comprising a C2 layer containing a functionalized fluoropolymer layer bonded to a C3 or C4 containing a polyolefin. It turns out that this type of multilayer structure has poor resistance to aging when in contact with hot water.

There is still a need to formulate new binders that can fasten a fluorinated polymer to another polymer which is incompatible him. It is especially a need to develop new binders for manufacturing multilayer structures adapted especially for the transport of drinking water, especially hot water.

What a problem solved by the invention is to provide a multilayer structure which has good adhesion between a layer comprising a fluoropolymer and a layer of polymer incompatible with said fluoropolymer.

Another object of the present invention is to provide a multilayer structure having a satisfactory level of adhesion, e.g., substantially greater than or equal to 30N / cm between the layer comprising a fluorinated polymer and the incompatible polymer layer, this adhesion being measured by longitudinal coat, that is to say, longitudinal cutting of a tube and measure of adherence by the method of "90 ° peel

imposed "at a temperature of 23 ° C and a pulling rate of 50mm / min, the lever arm of the compound or layer (s) containing fluoropolymer having a total thickness between 200 and 400μηη.

Another object of the present invention is to provide a multilayer structure which can resist to aging (in particular at least 2000 hours) in water at a temperature equal to or higher than 80 ° C, in particular equal to 95 ° C, this water which may contain chlorinated agents used for the treatment of water.

SUMMARY OF THE INVENTION

To achieve one of the aforementioned objects, the present invention relates to a multilayer structure comprising in order:

- optionally a layer A comprising at least one fluoropolymer,

- a layer B comprising at least one fluoropolymer and an acrylic copolymer comprising monomers having a plurality of functional groups X,

- a layer C comprising, and preferably consisting of at least one first olefin polymer comprising monomer having a plurality of functional groups Y capable of interacting with the functional groups X,

- optionally, an intermediate layer D comprising at least one second olefin polymer comprising monomer having a plurality of functional groups Z capable of interacting with said functional groups Y, said second olefin polymer being different from that / those comprised in said layer C,

- E a layer comprising at least one polymer, and in particular an olefin polymer incompatible with said fluoropolymer of said layer A and / or said layer B.

The applicant has indeed demonstrated that it was possible to obtain a better adhesion between a fluoropolymer and a polymer incompatible with said fluoropolymer, such polymers being included in two non-adjacent different layers by means of a set formed from a layer comprising a blend of a fluoropolymer with an acrylic copolymer having functional group, such as

above, said layer being secured to at least one intermediate layer containing at least one functionalized olefin polymer. Thus a single multilayer structure to manufacture and inexpensive.

The various layers of the structure component may also comprise additives, in particular rheological properties, impact modifiers, pigments, and any other additive known to those skilled in the art.

In the case of use of a multilayer structure of the invention in contact with drinking water, the multilayer structure according to the invention preferably comprises a layer A in direct contact with the drinking water. The presence of this layer A provides improved chemical resistance to water treatment agents and resistance to biofilm formation on the surface of the material in direct contact with drinking water.

The present invention also relates to a tube for transporting fluids, in particular liquids such as water or for food liquids, said tube being adapted particularly for the transport of drinking water, in particular potable hot water.

EMBODIMENTS DESCRIPTION OF THE INVENTION

The invention is now described in more detail and not limited to the following description.

The present invention relates to a multilayer structure comprising in order:

- optionally a layer A comprising at least one fluorinated polymer, - a layer B comprising at least one fluoropolymer and an acrylic copolymer comprising monomers having a plurality of functional groups X,

- a layer C comprising, and preferably consisting of at least one first olefin polymer comprising monomer having a plurality of functional groups Y capable of interacting with the functional groups X,

- optionally, an intermediate layer D comprising at least one second olefin polymer comprising monomer having a plurality of functional groups Z capable of interacting with said

functional groups Y, said second olefin polymer being different from that / those comprised in said layer C,

- E a layer comprising at least one polymer, and in particular an olefin polymer incompatible with said fluoropolymer of said layer A and / or said layer B.

Typically, the monomers carrying functional groups Y are unsaturated epoxides or vinyl esters of saturated carboxylic acids.

These layers are described in detail below.

layer B

The layer B comprises at least one fluorinated polymer and acrylic copolymer containing monomer having a plurality of functional groups X

According to one embodiment, the functional groups X are carboxyl groups.

According to one embodiment, the functional groups X are carboxylic acid anhydride groups.

According to one embodiment, the functional groups X are mixtures of carboxyl groups and carboxylic acid anhydride. According to one embodiment, the acrylic copolymer is a copolymer of methyl methacrylate and glutaric anhydride or methyl methacrylate copolymer and methacrylic acid or a mixture of these two copolymers.

Advantageously, the acrylic copolymer of the layer B comprises, by weight, from 1% to 50%, preferably between 1% and 25%, inclusive, of monomers carrying a functional group X described above.

Preferably, said layer B is free of alpha-olefin polymer comprising at least one functional group selected from carboxyl, acid anhydride, hydroxyl and epoxy.

The fluoropolymer of the layer A and the layer B are not limiting of the invention. They are identical in both layers or not. The layers may also comprise a mixture of at

least two fluoropolymers, which mixture is identical or not in the layers A and B.

Thus, the (s) polymer (s) fluoropolymer (s) of the layers A and B is / are selected (s) from vinylidene fluoride homopolymer (PVDF) and copolymers of vinylidene fluoride and at least one other comonomer. According to one embodiment the comonomer of VDF is selected from vinyl fluoride, trifluoroethylene (VF3), chlorotrifluoroethylene (CTFE), 1, 2-difluoroethylene, tetrafluoroethylene (TFE), hexafluoropropylene (HFP), perfluoro (alky vinyl) ethers such as perfluoro (methyl vinyl) ether (PMVE), perfluoro (ethyl vinyl) ether (PEVE), perfluoro (propyl vinyl) ether (PPVE), perfluoro (1, 3-dioxozole); perfluoro (2,2diméthyl-1, 3dioxole) (PDD), the product of formula CF 2 = CFOCF 2 CF (CF 3) OCF 2 CF 2 X wherein X is SO 2 F, CO 2H, CH 2 OH; CH 2 OCN or CH 2 OPO 3 H, the product of formula CF 2 = CFOCF 2 CF 2 SO 2 F; the product of formula F (CF 2 ) n CH 2 OCF = CF 2 wherein n is 1, 2,3,4 or 5, the product of formula RiCH 2 OCF = CF 2 wherein R is hydrogen or F (CF 2 ) Z and z is 1, 2, 3, or 4; the product of formula R3OCF = CH 2 wherein R 3 is F (CF 2 ) Zand bromotrifluoroethylene. The copolymer may also comprise non-fluorinated monomers such as ethylene.

According to one embodiment a copolymer of VDF (vinylidene fluoride) used for layer A and layer B, the comonomer is hexafluoropropylene (HFP).

According to one embodiment which may be combined with any of the above embodiments, the fluoropolymer of the layer A is a vinylidene fluoride homopolymer, the fluoropolymer of the layer B is a vinylidene fluoride homopolymer but different from that of the layer A.

layer C

The layer C comprises, and preferably consists of at least one first olefin polymer comprising monomer having functional groups Y capable of interacting with the functional groups X.

The monomers carrying functional groups Y are selected from:

- unsaturated epoxides, in particular esters and aliphatic glycidyl ethers such as allyl glycidyl ether, maleate and itaconate glicydyle acrylate and glycidyl methacrylate, as well as esters and ethers, alicyclic glycidyl; and

- vinyl esters of saturated carboxylic acids, especially vinyl acetate or vinyl propionate.

According to a particular embodiment of the layer C which can be combined with any of the embodiments of the other layers, the first olefin polymer is a copolymer of ethylene and at least one unsaturated polar monomer bearing functions Y in the preceding list, which contains by weight at least 50%, preferably more than 60% and preferably at least 65% ethylene.

According to a particular embodiment of the layer C which can be combined with any of the embodiments of the other layers, the first olefin polymer is a terpolymer of ethylene, at least one unsaturated polar monomer bearing functions Y of the previous list and (meth) acrylates Ci-Ce, in particular (meth) acrylate, propyl, butyl, 2-ethylhexyl, isobutyl, cyclohexyl. This terpolymer contains by weight at least 50%, preferably more than 60% and preferably at least 65% ethylene.

The first olefin polymer may comprise from 50 to 99.9 weight% ethylene, preferably 60 to 99.9%, more preferably from 65 to 99.9% and from 0.1 to 50%, preferably from 0.1 to 40%, even more preferably from 0.1 to 35% of at least one unsaturated polar monomer bearing Y functions of the previous list. Terminals of the aforementioned intervals correspond to mass values, the olefinic polymer of the invention may contain.

layer D

According to one embodiment which may be combined with the other embodiments mentioned above with reference to layers A, B, C and E, the structure of the invention comprises an intermediate layer D.

The intermediate layer D comprises at least one second olefin polymer comprising monomer having functional groups Z capable of interacting with said functional groups Y, said second olefin polymer being different from that / those comprised in said layer C.

The functional groups Z are selected from unsaturated carboxylic acids, unsaturated dicarboxylic acids having 4 to 10 carbon atoms and their anhydride derivatives.

Said second olefin polymer is selected from polymers obtainable by grafting at least one unsaturated polar monomer having a functional group Z, on at least one propylene homopolymer or a copolymer of propylene and an unsaturated polar monomer selected from alkyl esters Ci-or glycidyl esters of unsaturated carboxylic acids or unsaturated carboxylic acid salts or mixtures thereof.

Advantageously, the polymer mass comprises a quantity of said grafting monomer equal to or less than 5%.

The second olefinic polymer is preferably, independently of the other components of the other layers, a polypropylene grafted maleic anhydride.

E layer

According to a particular embodiment, which can be combined with any of the aforementioned embodiments, said multilayer structure optionally includes the layer A, layer B and layer C and E. The layer E comprises at least one polymer, and including a third olefin polymer incompatible with said fluoropolymer of said layer a and / or said layer B.

When said multi-layer structure includes the layer A and layers B, C and E, said incompatible polymer of the layer E is selected from ethylene homopolymers, copolymers of ethylene and at least one other monomer selected from alpha olefins, alkyl acrylates, vinyl acetates and mixtures of these polymers.

The incompatible polymer contained in the layer E is a polymer comprising predominantly ethylene monomers and / or propylene. It may be a polyethylene homo- or copolymer, the comonomer being selected from alpha-olefins (especially propylene, butene, hexene, octene), alkyl acrylates and acetates vinyl. It can also be a propylene homo- or copolymer, the comonomer being chosen from alpha-olefins (especially ethylene, butene, hexene, octene). The incompatible polymer can also be a mixture of these various polymers.

The polyethylene may be in particular high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), very low density polyethylene (VLDPE). The polyethylene may be obtained using a Ziegler-Natta catalyst, Phillips or metallocene or by the high pressure process. These may also be a crosslinked polyethylene (PEX). PEX has better mechanical properties (especially regarding the crack resistance) and improved chemical resistance compared to a non-crosslinked PE. The polyethylene can be crosslinked with a radical initiator of the peroxide type (PEX-a). The cross-linked polyethylene may also be for example a polyethylene containing hydrolysable silane groups (PEX-b) allowing the formation of Si-O-Si chains connecting the polyethylenes therebetween. The polyethylene can also be

crosslinked using radiation, e.g., gamma radiation (PEX-c).

When the multilayer structure of the invention comprises a layer, said polymer of said layer E is preferably selected from propylene homopolymers, copolymers of propylene and an alpha-olefin and mixtures of these polymers. The polypropylene is preferably an isotactic or syndiotactic polypropylene.

The manufacturing method of the multilayer structure of the invention is not limiting. It can be obtained, for example, by coextrusion.

The multilayer structure according to the invention can be used to form tubes, used as pipe for transporting fluids, in particular liquids, in particular for transporting water, preferably potable water and heated potable water in particular. The thickness of the multilayer structure according to the invention varies from 0.5 to 10 mm, preferably from 0.8 to 5 mm and even more preferably 1 to 3 mm, inclusive.

Advantageously, in the case of a tube, said layer E is the outer layer of said tube. It ensures the mechanical strength of the tube.

Advantageously, the tube may comprise an inner layer A that prevents biofilm formation on the inner surface of the tube. The combination of the layers B and C ensures high adhesion between the various layers of the structure, even in case of hot water circulation.

The tube may comprise layers B, C and E or the layers A, B, C and E or the layers B, C, D and E or the layers A, B, C, D and E. Preferably, it contains the layers A, B, C and E. When present, the D layer is located between the layer C and the layer E.

The present invention also relates to the use of a tube comprising the layers B, C and E for the transport of fluids, in particular liquids, in particular for transporting water, for example drinking and industrial water, especially hot.

The present invention also relates to the use of a tube having the layers B, C, D and E above for the transport of drinking water.

The present invention also relates to the use of a tube having the layers B, C, D and E above for the transport of drinking water and especially drinking hot water.

The present invention also relates to the use of a tube having the layers A, B, C, D and E above for the transport of drinking water and especially drinking hot water.

The layers A and B may contain one or more identical or different fluoropolymers fluoropolymers.

Definitions:

The term "interact" with reference to the functional groups X, Y and Z includes any type of interaction may cause the bonding of the layers; it may be a chemical reaction between the functional groups of the layers in contact, diffusion channels at the interface, the macromolecules of one layer being nested into those of the adjacent layer, of the intermolecular bonds of Van der Waals or hydrogen bonds, or a mixture of these interactions.

The term "acrylic copolymer comprising monomers having a plurality of functional groups X", contained in the layer B, refers to a copolymer comprising:

- the kind of reasons:

wherein Ri and R2 represent a hydrogen atom or an alkyl, linear or branched, having 1 to 20 carbon atoms; R1 and R2 may be the same or different;

- and kind of grounds:

wherein R3 is a hydrogen atom or an alkyl, linear or branched, containing from one to twenty carbon atoms.

The latter pattern may be in its acid form, but also in its anhydride derivatives or a mixture thereof. When in the form of anhydride, this pattern can be represented by the formula:

wherein R 4 and R 5 represent a hydrogen atom or an alkyl, linear or branched, having 1 to 20 carbon atoms; R 4 and R 5 may be the same or different.

According to one embodiment, the acrylic copolymer comprises up to 50% by weight of the ground as acid or its anhydride derivative or a mixture of both. Advantageously the acrylic copolymer comprises up to 25% by weight of the ground as acid or its anhydride derivative or a mixture thereof.

In another embodiment, Ri and R2 are methyl. In this case the binder is based on PMMA.

According to another embodiment, R3 represents hydrogen or methyl in the case where the pattern that carries the is in acid form, and R 4 and R 5 represents hydrogen or methyl in the case where the pattern is in the form anhydride .

The term "water" refers to water that has been treated to drinking water and therefore containing chemicals for water treatment such as those referenced in the prior art.

The terms "adapted or transportation of drinking water" means that the polymer in question contains components that are referenced to a list of components considered suitable for transporting drinking water selected from the following: "WRAS certificate selon to Standard BS6920 "for the UK," KTW certificate to KTW 1 .3.13 Regulations "for Germany," KIWA certificate selon Regulations BRL 2013 "for the Netherlands, the ACS certificate according to the circular issued by the department french health: DSGA / S4 No. 2000/232 dated 27/04/2000 and the Italian decree DM 174 (Ministerial Decree No. 174 dated 06/04/2007).

EXAMPLES

The following examples illustrate the invention without limiting it.

Used materials :

• PVDF-1 homopolymer with a melt index PVDF (MFI) = 20 g / 10min (230 ° C, 3.8kg) and melting temperature of about 170 ° C

• PVDF-2: PVDF homopolymer with a melt index (MFI) = 2 g / 10min (230 ° C, 5kg) and melting temperature of about 170 ° C

• PVDF-3: PVDF homopolymer grafted with maleic anhydride with a melt index (MFI) = 15 g / 10min (230 ° C, 3.8kg) and melting temperature of about 170 ° C. Used in comparison PVDF + 2 mixes acrylic copolymers described below.

• CA-1: Copolymer of methyl methacrylate and 1, 3-dimethyl glutaric anhydride and melt flow index (MFI) = 3.5 g / 10min (230 ° C, 3.8kg)

· CA-2: methyl methacrylate copolymer and methacrylic acid with a melt index (MFI) = 2 g / 10min (230 ° C, 3.8kg)

• CA-3: methyl methacrylate copolymer and methacrylic acid with a melt index (MFI) = 3.5 g / 10min (230 ° C, 3.8kg) • POE-1: Copolymer of ethylene and glycidyl methacrylate with a melt flow index (MFI) = 5 g / 10min (190 ° C, 2.16 kg), density 0.94 g / cm 3 at 23 ° C and melting point of 105 ° C.

• POF-2: Polypropylene grafted with maleic anhydride with a melt index (MFI) = 7 g / 10min (230 ° C, 2.16 kg)

• PE: melt flow index of polyethylene (MFI) = 0.2 g / 10min (190 ° C, 2.16 kg) and density 0.938 g / cm 3 at 23 ° C

• PP: Polypropylene melt flow index (MFI) = 0.25 g / 10min (230 ° C, 2.16kg) and density = 0.905 g / cm 3 at 23 ° C

multilayer structures prepared:

Multilayer pipe S1

The multilayer pipe S1 is formed of four successive layers (from inside outwards):

A layer: PVDF-1

Layer B: PVDF-2 + acrylic copolymer selected from CA-1, CA-2, CA-3 or PVDF-3 (Comparative Example)

Layer C: POF-1

Couche E: ON

multilayer pipe S2

The multilayer tube S2 is formed of five layers (from inside outwards):

A layer: PVDF-1

Layer B: PVDF-2 + acrylic copolymer selected from CA-1, CA-2, CA-3 or PVDF-3 (Comparative Example)

Layer C: POF-1

Layer D: POF-2

E-layer: PP

Multilayer pipe S3

S3 multilayer pipe is formed of three layers (from inside outwards):

Layer B: PVDF-2 + acrylic copolymer selected from CA-1, CA-2, CA-3 or PVDF-3 (Comparative Example)

Layer C: POF-1

Couche E: ON

Mixtures of 2 and PVDF-acrylic copolymer used in layer B of these structures S1, S2 and S3 are prepared beforehand in co-rotating twin-screw extruder under conditions complying with the rules of the art at a set temperature 220 ° C.

Measurement of accession:

The interlayer is measured by a peel test adhesion according to the method of "90 ° peel imposed" at a temperature of 23 ° C and a stretching rate of 50mm / min. The lever arm is composed of the layers A and B and has a total thickness between 200 and 400μηη. The requested interface is thus that between the layers B and C. The extent of adhesion is carried out 24 hours after the completion of the multilayer tube. Accession measures following the same protocol are also carried out after the multilayer tube was immersed in 1000 and 2000h in water at 95 ° C (pressure = 1 bar).

example 1

A multilayer pipe structure S1 is formed by coextrusion using a device manufactured by McNeil Akron Repiquet. Coextrusion of these products is carried out at a temperature of 245 ° C. The tube has an outer diameter of 20 mm and a total thickness of 2 mm. The thickness distribution in the structure is as follows:

- Layer A: 200 μηη

- Layer B: 100 pm

- Layer C: 100 microns

- Layer E: 1600 pm

The nature and concentration of the acrylic copolymer in the layer B is variable. For comparison is used for the layer B-3 PVDF polymer.

Table I below shows the different mixtures used in the B layer and the results of adhesion tests. The number in the bottom of each box corresponds to the standard deviation of the adhesion value indicated above.

Table I

NP letters shown in Table II indicate that the primer is not propagatable which means that the adhesion between layers B and C is so high that by exerting a force on the lever arm, it exceeds its constraint at break and the sample breaks without being able to separate the two aforementioned layers.

It is found that superior adherence to 40N / cm are reached with all 3 tested acrylic copolymers and retained after aging. Use of a binder according to the invention comprising an acrylic copolymer having a functional group X thus provides improved adhesion relative to the functionalized PVDF PVDF-3. The use of the latter clearly induces a progressive loss of adhesion at the interface between layers B and C in a water exposure at 95 ° C, followed by debonding at the interface between the layers . The multilayer pipe according to the invention thus has a better resistance to aging, in particular in hot water. The

example 2

A multilayer pipe structure S1 is formed by coextrusion using a device manufactured by McNeil Akron Repiquet. Coextrusion of these products is carried out at a temperature of 245 ° C. The tube has an outer diameter of 20 mm and a total thickness of 2 mm. The thickness of layer B varies within the structure which leads to the following thickness distribution:

- Layer A: x pm

- Layer B: 100 pm

- Layer C: 100 μηη

- Layer E: 1800 - x pm

The nature and concentration of the acrylic copolymer in the layer B is variable. In comparison, using the 3-PVDF polymer in the layer B. The adhesion measurements at the interface between layers B and C are shown in Table II.

Tableau II

There is an increase in the thickness of the layer A thus the thickness of the internal lever arm causes a rise in income

measured during the adhesion test. This illustrates the mechanical contribution to the deformation of the lever arm in this measurement. A comparison of the level of adhesion obtained in two different structures can not be that thick constant lever arm, composition of the lever arm as close as possible and the same temperature.

Moreover, this example also shows that, in the case of an inner layer of PVDF-1 = 10Όμιτι, a gradual decrease adhesion with the binder is observed "PVDF-2 + C-2" while the level of accession measured under the same conditions for the binder "PVDF-2 + CA-1" remains stable. The presence of anhydride groups allows better maintenance of membership in this structure.

example 3

A multilayer pipe structure S2 is formed by coextrusion using a device manufactured by McNeil Akron Repiquet. Coextrusion of these products is carried out at a temperature of 245 ° C. The tube has an outer diameter of 32 mm and a total thickness of 3 mm. The thickness distribution in the structure is as follows:

- Layer A: 300 μηη

- Layer B: 100 μιτι

- Layer C: 500 μιτι

- Layer D: 500 μιτι

- Layer E: 1600 μηη

The nature and concentration of the acrylic copolymer in the layer B is variable. In comparison, using the 3-PVDF polymer in layer B.

Table III below shows the various mixtures used in the layer B and membership generated at the interface between the layers B and C. adhesions greater than 40N / cm are reached with all 3 tested acrylic copolymers and retained after aging . This is not the case when a functionalized PVDF PVDF-3 is used as a binder, with which there is a net loss of adhesion after 1000h aging in water at 95 ° C.

mass fraction

acrylic copolymer Accession to t0 + Membership tO + 1000h layer B

24 in the B layer (N / cm) hot water (N / cm)

PVDF-3 47,2 12,3

100

(Control) 4 7 2.3

10 61 ,4 44,5

CA-1

9,2 3,8

10 54,9 57,9

CA-2

5,6 4,6

10 135,2 85,5

CA-3

6,8 6, 1

Table III

example 4

Multilayer tube structure S1 and S3 are formed by coextrusion using a device manufactured by McNeil Akron Repiquet. Coextrusion of these products is carried out at a temperature of 245 ° C. The tube has an outer diameter of 20 mm and a total thickness of 2 mm. The thickness distribution within the structures is as follows:

S1:

Layer A: 200 μηη

Layer B: 100 pm

C layer: 100 pm

Layer E: 1600 μηη

S3:

Layer B: 300 μηη

C layer: 100 pm

Layer E: 1600 μηη

The total thickness of layers A and B containing fluorinated polymers remain the same in tubes 2 structures. The nature and concentration of the acrylic copolymer in the layer B is variable.

Table IV

The data presented in Table IV show that the interfacial adhesions, even after aging do not vary depending on the presence of an inner layer without acrylic copolymer. The choice of the use of this optional additional layer then depends on other desired properties such as permeability, chemical sensitivity or the surface appearance of the tube.

CLAIMS

1. Multilayer structure comprising, in order:

- a layer B comprising at least one fluoropolymer and an acrylic copolymer comprising monomers having functional groups X,

- a layer C consisting of at least one first olefin polymer comprising monomers having functional groups Y capable of interacting with the functional groups X, monomers bearing functional groups Y are unsaturated epoxides or vinyl esters of saturated carboxylic acids,

and

- E a layer comprising at least one polymer, in particular an olefin polymer, which is incompatible with said fluoropolymer of said layer B.

2. Multilayer structure according to claim 1, further comprising a layer A comprising at least a fluorinated polymer, said layer A juxtaposing layer B.

3. Multilayer structure according to one of claims 1 and 2 further comprising, between the layer C and the layer E, D an intermediate layer comprising at least a second olefin polymer comprising monomers having functional groups Z capable of interacting with said functional groups Y, said second olefin polymer being different from that / those comprised in said layer C.

4. Multilayer structure according to one of claims 1 to 3 characterized in that said functional groups X are selected from carboxyl, carboxylic acid anhydrides, and mixtures of these groups.

5. Multilayer structure according to any one of the preceding claims, characterized in that:

- unsaturated epoxides are selected from esters and aliphatic glycidyl ether such as allyl glycidyl ether, maleate and itaconate glicydyl acrylate and glycidyl methacrylate, and the esters and glycidyl ethers alicyclic ; and in that

- vinyl esters of saturated carboxylic acids are vinyl acetate or vinyl propionate acetate.

6. Multilayer structure according to any one of claims 3 to 5, characterized in that said functional groups Z are selected from unsaturated carboxylic acids, unsaturated dicarboxylic acids having 4 to 10 carbon atoms and their anhydride derivatives.

7. Multilayer structure according to any one of the preceding claims, characterized in that said acrylic copolymer of said layer B contains alkyl acrylate units, particularly alkyl methacrylate.

8. Multilayer structure according to any one of the preceding claims, characterized in that said acrylic copolymer of the layer B comprises, by weight, from 1% to 50%, preferably from 1% to 25%, of monomers carrying functions X .

9. The multilayer structure according to any one of the preceding claims, characterized in that said layer B is free of alpha-olefin polymer comprising at least one functional group selected from a carboxyl group, an acid anhydride group, a hydroxyl group and a epoxy group.

10. Multilayer structure according to any one of the preceding claims, characterized in that said first olefin polymer of said layer C comprises by weight at least 50%, preferably more than 60%, preferably at least 65% of ethylene comonomer in addition unsaturated comonomer having polar functional groups Y.

January 1. Multilayer structure according to any one of the preceding claims, characterized in that said first olefin polymer of said layer C is a terpolymer of ethylene, an unsaturated polar comonomer having functional groups Y and a (meth) acrylate alkyl Ci-Ce, in particular (meth) acrylate, propyl, butyl, 2-ethylhexyl, isobutyl or cyclohexyl.

12. Multilayer structure according to any one of the preceding claims, characterized in that said second olefin polymer of said layer D is obtained by grafting at least one unsaturated polar monomer having a functional group Z on at least one propylene homopolymer or a copolymer of propylene and an unsaturated polar monomer selected from alkyl esters of Ci-Ce or glycidyl esters of unsaturated carboxylic acids or unsaturated carboxylic acid salts or mixtures thereof.

13. Multilayer structure according to any one of claims 1 to 12, characterized in that, when said multilayer structure optionally includes the layer A and layers B, C and E, said incompatible polymer of the layer E is selected from homopolymers ethylene, copolymers of ethylene and at least one other monomer selected from alpha-olefins, alkyl acrylates, vinyl acetates and mixtures of these polymers.

14. Multilayer structure according to any one of claims 3 to 12, characterized in that, when said multilayer structure comprises a layer D, said incompatible polymer of said layer E is selected from homopolymers of propylene, copolymers of propylene and an alpha-olefin and mixtures of these polymers.

15. Tube characterized in that it comprises a multilayer structure according to any one of the preceding claims and in that said E layer is the outer layer of said tube.

16. Use of the tube according to claim 15 for the transport of fluids, in particular liquids, in particular water.

17. Use according to claim 16 for transporting drinking water and especially drinking hot water.