WO2007006897A2

WO2007006897A2 - Multilayer insulation structure

Info

Publication number: WO2007006897A2
Application number: PCT/FR2006/001571
Authority: WO
Inventors: Anthony Bonnet; Michael Werth
Original assignee: Arkema France
Priority date: 2005-07-05
Filing date: 2006-07-04
Publication date: 2007-01-18
Also published as: WO2007006897A3

Abstract

The invention relates in a first form to the use of an insulation structure for electric or optical cables, comprising an internal layer L1 of: a) at least one polyolefin, b) or at least one functionalised polyolefin, c) or a mixture of the two, a layer L2 of adhesive binder, a layer L3 with at least one fluorinated polymer to which at least one unsaturated monomer has been grafted by radiation, optionally mixed with at least one fluorinated polymer, optionally a layer L4 with at least one fluorinated polymer. In a second form the structure comprises an internal layer L'1 of: a) at least one functionalised polyolefin Pl with chemical functions reacting with the grafted unsaturated monomer on the graft fluorinated polymer L'2, b) optionally at least one polyolefin, c) and/or optionally one other functionalised polyolefin P2, a layer L'2 with at least one fluorinated polymer to which at least one unsaturated monomer has been grafted by radiation and optionally mixed with at least one fluorinated polymer, optionally a layer L'3 comprising at least one fluorinated polymer. The invention further relates to the electric and/or optical cable itself.

Description

INSULATING MULTILAYER STRUCTURE

The present invention relates to an insulating multilayer structure for electric and / or optical cables. This structure is based on a fluoropolymer modified by radiation grafting, used alone or as a mixture, and a functionalized polyolefin, used alone or as a mixture.

[The technical problem] Electrical cables insulated with multilayer structures comprising an inner layer of polyethylene and an outer layer of a fluoropolymer (for example polyvinylidene fluoride or PVDF) have been marketed for thirty years. In addition to their electrical insulation function, multilayer structures of this type can protect the electrical cable mechanically and chemically. However, the inner layer and the outer layer can delaminate easily because of the lack of adhesion between the two types of polymers, which have no chemical affinity for each other, resulting in embrittlement of the entire electric cable. It is therefore desirable to be able to improve the adhesion between the layers to improve the properties of the electric cables.

The Applicant has developed an insulating multilayer structure comprising a layer based on a polyolefin and / or a functionalized polyolefin and a fluoropolymer layer modified by radiation grafting to solve the delamination problem mentioned above. . [Previous Δrt]

US application US 2004/0045735 A1 discloses an electrical cable insulated by a multilayer structure illustrated by several variants. According to one of the variants, one of the layers is composed of an ethylene-tetrafluoroethylene copolymer and the other layer of an ethylene-tetrafluoroethylene copolymer on which is grafted a carboxylic acid, carboxylic acid salt or unsaturated anhydride function. .

US application US 2003/0051900 A1 discloses an electrical cable insulated by a multilayer structure comprising an inner layer of a mixture of a functionalized polyolefin and a polyolefin and an outer layer of a fluoropolymer, the two layers being crosslinked by radiation .

The international application WO 2005/005564 discloses a heat-shrink tube (in English) comprising an inner layer of fluoropolymer crosslinkable by irradiation and an outer layer of a radiation-modified polymer.

The international application WO 2000/17889 of the company RAYCHEM relates to the insulation of electric cables by a multilayer structure. The multilayer structure comprises an inner layer based on a functional polyolefin and an outer layer based on a fluoropolymer, the two layers being irradiated with ionizing radiation of at least 2 Mrad. Irradiation of the fluoropolymer occurs once the cable is isolated by the multilayer structure. The irradiation makes it possible to crosslink the polymers of each layer and to ensure strong adhesion between the layers.

US Pat. No. 6156847 discloses a copolymer of VDF and chlorotrifluoroethylene crosslinked with a crosslinking agent (for example example triallyl cyanurate) and ionizing radiation, which can be used to isolate an electric cable.

US Pat. No. 3,580,829 describes the crosslinking of PVDF consisting in using a crosslinking agent (for example triallyl cyanurate or N, N'-ethylene-bis-maleimide). There is no mention of the use of PVDF and crosslinked to isolate an electrical cable.

European Patent EP 0119725 B1 discloses a multilayer structure having a layer based on a composition comprising a fluoropolymer and a layer based on a polymer incompatible with the composition, the whole being irradiated to adhere the two layers together after heating the interface between the two layers. There is no mention of the use of the laminate material to insulate an electrical cable. The irradiation of the fluoropolymer therefore takes place once the multilayer structure has been formed.

None of these documents refers to an electrical cable with an insulating multilayer structure of the same nature as that of the invention.

[Brief description of the invention]

According to the ^ERE form, the invention relates to the use of an insulating multilayer structure comprising arranged one against the other in the order indicated: • an inner layer L ₁ comprising: a) at least one polyolefin ; b) or at least one functionalized polyolefin; c) or a mixture of both;

An L 2 layer of adhesion binder; A layer L3 comprising at least one fluoropolymer on which has been grafted by irradiation at least one monomer - AT -

unsaturated, optionally in admixture with at least one fluoropolymer;

Optionally a layer L4 comprising at least one fluorinated polymer, for isolating an electrical and / or optical cable.

According to a ^2nd form, the invention relates to the use of an insulating multilayer structure comprising arranged one against the other in the order indicated: • an inner layer IΛ comprising: a) at least one functionalized polyolefin Pi which comprises chemical functions which react with the unsaturated monomer grafted onto the fluoropolymer grafted with L 2, b) and optionally at least one polyolefin, c) and / or optionally another functionalized polyolefin P2;

A layer L'2 comprising at least one fluoropolymer on which has been grafted by irradiation at least one unsaturated monomer, optionally mixed with at least one fluorinated polymer; Optionally an Layer 3 comprising at least one fluorinated polymer, for isolating an electrical and / or optical cable.

The invention also relates to the electric and / or optical cable itself.

The invention will be better understood on reading the detailed description which follows, non-limiting examples of implementation thereof, and on examining the appended figures.

[Detailed description] As regards the irradiated grafted fluoropolymer, this is obtained by a grafting process by irradiation of an unsaturated monomer on a fluoropolymer (which is described below). We will speak for simplification of fluoropolymer grafted by irradiation.

The fluoropolymer is premixed with the unsaturated monomer by all known melt blending techniques of the prior art. The mixing step is carried out in any mixing device such as extruders or kneaders used in the thermoplastics industry. Preferably, an extruder will be used to form the mixture into granules. The grafting takes place on a mixture (in the mass) and not on the surface of a powder as described for example in US Pat. No. 5,576,106.

Then, the mixture of the fluoropolymer and the unsaturated monomer is irradiated in the solid state with the aid of an electronic or photonic source under an irradiation dose of between 10 and 200 kGray, preferably between 10 and 150 kGray. Irradiation with a cobalt-60 bomb is particularly preferred.

The unsaturated monomer content which is grafted is 0.1 to 5% by weight (i.e., the unsaturated grafted monomer corresponds to 0.1 to 5 parts for 99.9 to 95 parts by weight). fluoropolymer), preferably from 0.5 to 5%, preferably from 1 to 5%. The grafted unsaturated monomer content is dependent on the initial content of the unsaturated monomer in the fluoropolymer / unsaturated monomer mixture to be irradiated. It also depends on the effectiveness of the grafting, and therefore the duration and energy of the irradiation.

The unsaturated monomer which has not been grafted and the residues released by the graft, in particular HF, are then optionally removed. This operation can be performed according to the known techniques of the skilled person. Vacuum degassing may be applied, possibly by applying heating at the same time. It is also possible to dissolve the modified fluoropolymer in a suitable solvent such as, for example, N-methylpyrrolidone, and then to precipitate the polymer in a non-solvent, for example in water or in an alcohol.

This is one of the advantages of this radiation grafting process that higher graft unsaturated monomer contents can be obtained than with conventional grafting methods using a radical initiator. Thus, typically, with the irradiation grafting method, it is possible to obtain contents greater than 1% (1 part of unsaturated monomer per 99 parts of the fluoropolymer), or even greater than 1.5%, which is not possible with a conventional grafting process in an extruder

On the other hand, the grafting by irradiation takes place at "cold", typically at temperatures below 100 ^° C., or even 50 ^° C., so that the mixture of the fluorinated polymer and the unsaturated monomer is not the same. molten state as for a conventional grafting process in extruder but in the solid state. An essential difference is therefore that, in the case of a semi-crystalline fluorinated polymer (as is the case with PVDF for example), the grafting takes place in the amorphous phase and not in the crystalline phase, whereas Homogeneous grafting occurs in the case of grafting in a melt extruder. The unsaturated monomer therefore does not distribute identically on the chains of the fluoropolymer in the case of irradiation grafting and in the case of grafting in an extruder. The modified fluorinated product therefore has a different distribution of the unsaturated monomer on the fluoropolymer chains compared to a product that would be obtained by grafting into an extruder. During this grafting step, it is preferable to avoid the presence of oxygen. A nitrogen or argon sweep of the fluoropolymer / unsaturated monomer mixture is therefore possible to remove oxygen.

The fluoropolymer modified by radiation grafting has all the characteristics of the fluoropolymer before its modification, in particular its very good chemical resistance and very good resistance to oxidation, as well as its thermomechanical behavior.

As regards the fluoropolymer, it is prepared by polymerization of one or more monomers of formula (I):

in which :

• X ₁ denotes H or F; X ₂ and X ₃ denote H, F, Cl, a fluorinated alkyl group of formula C _n FmHp- or a fluorinated alkoxy group C _n FmHpO-, n being an integer between 1 and 10, m an integer between 1 and 2n + 1), p being 2n + 1m.

The definition of the fluoropolymer applies to the fluoropolymer on which irradiation grafting takes place as well as to the unmodified fluoropolymer (i.e., which has not been modified by radiation grafting).

As examples of usable monomers, mention may be made of hexafluoropropylene (HFP), tetrafluoroethylene (TFE), vinylidene fluoride (VDF, CH ₂ = CF ₂ ), chlorotrifluoroethylene (CTFE), perfluoroalkyl vinyl ethers such as CF3- O-CF = CF ₂ , CF ₃ -CF ₂ -O-CF = CF ₂ or CFs-CF ₂ CF ₂ -O-CF = CF ₂ , 1-hydropentafluoropropene, 2-hydroxy- pentafluoropropene, dichlorodifluoroethylene, trifluoroethylene (VF3), 1,1-dichlorofluoroethylene.

The polymerization may also optionally include other non-fluorine-containing olefinic unsaturated monomers such as ethylene, propylene, butylene, and higher homologs. Diolefins containing fluorine may also be used, for example diolefins such as perfluorodiallyl ether and perfluoro-1,3-butadiene.

As examples of fluoropolymers, mention may be made of:

Homopolymers or copolymers of TFE, in particular PTFE (polytetrafluoroethylene), ETFE (ethylene-tetrafluoroethylene copolymer) as well as TFE / PMVE, TFE / PEVE, TFE / PPVE and E / TFE / HFP copolymers (ethylene-terpolymers); tetrafluoroethylene - hexafluoropropylene);

Homopolymers or copolymers of VDF, in particular PVDF and VDF-HFP copolymers;

• Homo- or copolymers of CTFE, in particular PCTFE (polychlorotrifluoroethylene) and E-CTFE (ethylene-chlorotrifluoroethylene copolymer).

Preferably, the fluoropolymer is a PVDF homopolymer or a VDF-HFP copolymer containing at least 50% by weight of VDF, advantageously at least 75% by weight of VDF and preferably at least 85% by weight of VDF. This fluoropolymer indeed has a good chemical resistance, especially UV, and it is easily transformed (more easily than PTFE or ETFE copolymers). Examples include in particular the following PVDF Kynar ^® 710 ^® Kynar 720, Kynar ^® 740 ^® Kynar 2850, Kynar ^® 3120 marketed by Arkema. Advantageously, the PVDF has a viscosity ranging from 100 Pa · s to 4000 Pa · s, the viscosity being measured at 230 ^° C., at a shear rate of 100 s ^-1 using a capillary rheometer. Indeed, these PVDF are well suited to extrusion and injection. Preferably, the PVDF has a viscosity ranging from 300 Pa.s to 1200 Pa.s, the viscosity being measured at 230 ^° C., at a shear rate of 100 s ^-1 using a capillary rheometer.

The polymerization is carried out according to the methods known in the state of the art of fluoropolymers. In particular, with regard to the processes for synthesizing PVDF, US Pat. No. 3,553,185 and EP 0120524 describe processes for the synthesis by aqueous suspension of vinylidene fluoride (VDF, CHb = CFa) and its polymerization. Patents US 4025709, US 4569978, US 4360652, US 626396 and EP 0655468 describe the methods for synthesizing PVDF by aqueous emulsification of VDF and its polymerization.

In general, the olefinic unsaturated fluorinated monomers can be polymerized and optionally copolymerized with nonfluorinated olefinic monomers in aqueous emulsions. The emulsions contain, for example, a water-soluble initiator such as an alkali metal or ammonium persulfate or an alkali metal permanganate, which produce free radicals, and also contain one or more emulsifiers such as alkali or ammonium metals of a perfluorooctanoic acid.

Other aqueous colloidal suspension methods use initiators substantially soluble in the organic phase, such as dialkyl peroxides, alkyl hydroperoxides, dialkyl peroxydicarbonates or azoperoxides, the initiator being associated with colloids of the methylcellulose type, methyl-hydroxypropyl celluloses, methyl-propyl celluloses and methyl-hydroxyethyl celluloses.

Fluoropolymers have the following advantages: they can be used over a wide range of temperatures (low glass transition temperature / high melting point);

they have excellent resistance to solvents;

- By their chemical structure, they have good flame retardant properties.

Regarding the unsaturated monomer, it has a C = C double bond and at least one polar function which may be a function: carboxylic acid, carboxylic acid salt,

carboxylic acid anhydride, epoxide, carboxylic acid ester, silyl, carboxylic amide,

- hydroxy, isocyanate.

Mixtures of several unsaturated monomers are also possible.

Unsaturated carboxylic acids having 4 to 10 carbon atoms and their functional derivatives, particularly their anhydrides, are particularly preferred unsaturated monomers. Examples of unsaturated monomers are methacrylic acid, acrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, undecylenic acid, allylsuccinic acid, and the like. cyclohex-4-ene-1,2-dicarboxylic acid, 4-methyl-cyclohex-4-ene 1,2-dicarboxylic acid, bicyclo (2,2, l) hept-5-ene-2,3-dicarboxylic acid, x _- methylbicyclo (2,2 l-hept-5-ene-2, 3-dicarboxylic acid, zinc, calcium or sodium undecylenate, maleic anhydride, itaconic anhydride, citraconic anhydride, dichloromaleic anhydride, difluoromaleic anhydride, itaconic anhydride, crotonic anhydride , acrylate or glycidyl methacrylate, allyl glycidyl ether, vinyl silanes such as vinyl trimethoxysilane, vinyl triethoxysilane, vinyl triacetoxysilane, gamma-methacryloxypropyltrimethoxysilane.

Other examples of unsaturated monomers include C ₁ -C ₈ alkyl esters or glycidyl ester derivatives of unsaturated carboxylic acids such as methyl acrylate, methyl methacrylate, ethyl acrylate, methacrylate and the like. ethyl acrylate, butyl acrylate, butyl methacrylate, glycidyl acrylate, glycidyl methacrylate, mono-ethyl maleate, diethyl maleate, monomethyl fumarate, dimethyl fumarate, monomethyl, and diethyl itaconate; amide derivatives of unsaturated carboxylic acids such as acrylamide, methacrylamide, maleic monoamide, maleic diamide, maleic N - monoethylamide, N, N - diethylamide maleic, N - maleic monobutylamide, N, N - dibuiylamide maleic, furamic monoamide, furamic diamide, fumaric N-monoethylamide, fumaric N, N-diethylamide, fumaric N-monobutylamide and furyl N, N-dibutylamide; imide derivatives of unsaturated carboxylic acids such as maleimide, N-butylmaleimide and N-phenylmaleimide; and metal salts of unsaturated carboxylic acids such as sodium acrylate, sodium methacrylate, potassium acrylate, potassium methacrylate and zinc, calcium or sodium undecylenates. Unsaturated monomers are those which have two C = C double bonds which could lead to crosslinking of the fluoropolymer, such as, for example, di- or triacrylates. From this point of view, maleic anhydride as well as zinc, calcium and sodium undecylenates are good graftable compounds because they have little tendency to homopolymerize or even to give rise to crosslinking.

Advantageously, maleic anhydride is used. This unsaturated monomer indeed offers the following advantages: it is solid and can be easily introduced with the fluoropolymer granules before mixing in the molten state,

it makes it possible to obtain good adhesion properties,

it is particularly reactive with respect to the functions of a functionalized polyolefin, especially when these functions are epoxide functions,

unlike other unsaturated monomers such as (meth) acrylic acid or acrylic esters, it does not polymerize and does not have to be stabilized.

In the mixture to be irradiated, the proportion of fluoropolymer is, by weight, between 80 to 99.9% for respectively 0.1 to 20% of unsaturated monomer. Preferably, the proportion of fluorinated polymer is from 90 to 99% for 1 to 10% of unsaturated monomer, respectively.

At the end of the mixing step, it is found that the mixture of the fluorinated polymer and the unsaturated monomer may have lost part of the unsaturated monomer which had been introduced at the beginning of the mixing step. The proportion of "lost" unsaturated monomer depends on the volatility and nature of the unsaturated monomer. In fact the monomer may have been degassed in the extruder or mixer and in this case it is recovered in the vent circuits. As regards the actual grafting step, the products recovered at the end of the mixing step are advantageously packaged in polyethylene bags and the air is removed and they are closed. As for the irradiation method, it is possible to use without distinction electron irradiation better known under the name beta irradiation and photon irradiation better known under the name gamma irradiation. Advantageously the dose is between 2 and 6 Mrad and preferably between 3 and 5 Mrad.

As regards the step of removing the ungrafted unsaturated monomer and the residues released by the grafting, it is possible to use any technique known to those skilled in the art. It is possible to wash with solvents inert with respect to the fluoropolymer and the functions grafted by irradiation. For example, when grafting maleic anhydride, one can wash with chlorobenzene. It is also more easily degassing by evacuating the product recovered at the end of the grafting step, possibly by heating.

As regards the polyolefin, this term denotes a polymer comprising predominantly ethylene and / or propylene units. It may be a polyethylene, homo- or copolymer, the comonomer being chosen from propylene, butene, hexene or octene. It may also be a polypropylene, homo- or copolymer, the comonomer being chosen from ethylene, butene, hexene or octene.

The polyethylene can be in particular high density polyethylene (HDPE), low density (LDPE), medium density (MDDE), linear low density polyethylene (LLDPE), very low density polyethylene (VLDPE). The polyethylene can be obtained using a Ziegler-Natta, Phillips or metallocene catalyst or by the process high pressure. Polypropylene is iso- or syndiotactic polypropylene.

It can also be a copolymer of ethylene and propylene (known as EPM) or a copolymer of ethylene, propylene and a diene (known as EPDM).

It can also be a crosslinked polyethylene (denoted PEX). PEX has better non-crosslinked PE than mechanical properties (especially crack resistance) and better chemical resistance. The crosslinked polyethylene may be, for example, a polyethylene comprising hydrolysable silane groups (as described in applications WO 01/53367 or US20040127641 A1) which has then been crosslinked after reaction between them silane groups. The reaction of silane groups Si-OR between them leads to Si-O-Si bonds which connect the polyethylene chains to each other. The content of hydrolysable silane groups may be at least 0.1 hydrolysable silane groups per 100 units -CH 2 - (determined by infrared analysis). Polyethylene can also be crosslinked by means of radiation, for example gamma radiation. It may also be a polyethylene crosslinked using a radical initiator of the peroxide type. It is therefore possible to use a PEX of type A (crosslinking using a radical initiator), type B (crosslinking with silane groups) or type C (crosslinking by irradiation).

It may also be a so-called bimodal polyethylene, that is to say composed of a mixture of polyethylenes having different average molecular weights as taught in WO 00/60001. As regards the functionalized polyolefin, this term denotes a copolymer of ethylene and / or propylene and at least one unsaturated polar monomer chosen from:

C ₁ -C ₅ alkyl (meth) acrylates, in particular methyl, ethyl, propyl, butyl, methyl (meth) acrylate,

2-ethylhexyl, isobutyl, cyclohexyl;

unsaturated carboxylic acids, their salts and their anhydrides, in particular acrylic acid, methacrylic acid, maleic anhydride, itaconic anhydride and citraconic anhydride;

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

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

The functionalized polyolefin can be obtained by copolymerization of ethylene and at least one unsaturated polar monomer selected from the above list. The functionalized polyolefin may be a copolymer of ethylene and a polar monomer from the above list or a terpolymer of ethylene and two polar unsaturated monomers selected from the above list. The copolymerization is carried out at high pressures higher than 1000 bar according to the so-called high-pressure process (described for example in documents FR-A-2498609, EP-A-0 174 244 or EP-A-0 177 378).

The functionalized polyolefin obtained by copolymerization comprises, by weight, from 50 to 99.9% of ethylene, preferably from 60 to 99.9%, even more preferably from 65 to 99% and from 0.1 to 50%, preferably from 0, 1 to 40%, even more preferably 1 to 35% of at least one polar monomer from the above list.

For example, the functionalized polyolefin is a copolymer of ethylene and an unsaturated epoxide, preferably glycidyl (meth) acrylate, and optionally a (C ₁ -C ₅ ) alkyl (meth) acrylate or a vinyl ester of saturated carboxylic acid. The content of unsaturated epoxide, especially glycidyl (meth) acrylate, is between 0.1 and 50%, advantageously between 0.1 and 40%, preferably between 1 and 35% and even more preferably between 1 and 20%. . This may include for example functionalized polyolefins sold by Arkema under the references Lotader ^® AX8840 (8% glycidyl methacrylate, 92% ethylene, melt index of 5 according to ASTM-D 1238), Lotader ^® AX8900 (8 % glycidyl methacrylate, 25% methyl acrylate, 67% ethylene, melt-index 6 according to ASTM D 1238), LOTADER® AX8950 (9% glycidyl methacrylate, 15% methyl acrylate, % ethylene, melt-index 85 according to ASTM D 1238).

The functionalized polyolefin may also be a copolymer of ethylene and an unsaturated acid anhydride, preferably maleic anhydride, and optionally a (C ₁ -C ₅ ) alkyl (meth) acrylate or a vinyl ester of saturated carboxylic acid. The anhydride content of unsaturated acid, especially maleic anhydride, is between 0.1 and

50%, preferably between 0.1 and 40%, preferably between 1 to 35%, more preferably between 1 and 10%. It may be, for example, functionalized polyolefins marketed by the company

ARKEMA under the references Lotader ^® 2210 (2.6% maleic anhydride, 6% of butyl acrylate and 91.4% ethylene, melt-inder 3 according to ASTM D 1238), Lotader ^® 3340 (3% maleic anhydride, 16% butyl acrylate and 81% ethylene, ASTM melt-index 5

D 1238), Lotader ^® 4720 (0.3% maleic anhydride, 30% of ethyl acetate and 69.7% ethylene acrylate, melt-index 7 according to ASTM D 1238), Lotader ^® 7500 (2.8% maleic anhydride, 20% of butyl acrylate and 77.2% ethylene, melt-index 70 according to ASTM D 1238), OREVAC® 9309, Orevac ^® 9314, Orevac ^® 9307Y , OREVAC® 9318, OREVAC® 9304 or OREVAC® 9305.

Functionalized polyolefin also refers to a polyolefin on which is grafted by radical means an unsaturated polar monomer from the above list. The polyolefin is chosen from the previous list. The grafting takes place in an extruder or in solution in the presence of a radical initiator. As an example of a radical initiator, t-butyl hydroperoxide, cumene hydroperoxide, di-isopropylbenzene hydroperoxide, di-t-butylperoxide, t-butyl hydroperoxide may be used. butyl-cumyl-peroxide, dicumyl-peroxide, 1,3-bis (t-butylperoxyisopropyl) benzene, benzoyl peroxide, iso-butyryl-peroxide, bis-3,5,5-trimethyl hexanoyl peroxide or methyl ethyl ketone peroxide. The term copolymer is broadly defined as described, for example, in the ES Wilks IUPAC Nomenclature Guide or in IUPAC. Basic definitions of terms relating to polymers, Pure Appl. Chem. 40, 477-491 (1974). It therefore also includes graft copolymers. The grafting of an unsaturated polar monomer on a polyolefin is known to those skilled in the art, for more details, reference may be made for example to EP 689505, US 5235149, EP 658139, US 6750288 B2, US6528587 B2. The polyolefin on which the unsaturated polar monomer is grafted may be a polyethylene, in particular high density polyethylene (HDPE) or low density polyethylene (LDPE), linear low density polyethylene (LLDPE) or very low density polyethylene (VLDPE). The polyethylene can be obtained using a Ziegler-Natta, Phillips or metallocene catalyst or by the high-pressure process. The polyolefin may also be a polypropylene, in particular an iso- or syndiotactic polypropylene. It may be, for example, functionalized polyolefins marketed by ARKEMA under the OREVAC® references. 18302, 18334, 18350, 18360, 18365, 18370, 18380, 18707, 18729, 18732, 18750, 18760, PP-C ₅ CA100.

The polymer on which the unsaturated polar monomer is grafted may also be a copolymer of ethylene and at least one unsaturated polar monomer chosen from:

C ₁ -C ₅ alkyl (meth) acrylates, especially methyl, ethyl, propyl, butyl, 2-ethylhexyl, isobutyl or cyclohexyl (meth) acrylate; vinyl esters of saturated carboxylic acids, in particular vinyl acetate or vinyl propionate. It may be, for example, functionalized polyolefins sold by the company Arkema under the references OREVAC 18211, 18216 or 18630. According to another example, if an unsaturated epoxide, for example glycidyl methacrylate, has been grafted onto the fluoropolymer, the functionalized polyolefin layer may consist of a copolymer of ethylene, of a carboxylic acid anhydride, for example maleic anhydride, and optionally of an alkyl acrylate, the copolymer of ethylene being optionally mixed with a polyolefin.

The L 2 layer may comprise a single functional polyolefin or a mixture of several functional polyolefins, optionally mixed with a polyolefin. It may be, for example, a mixture of a copolymer of ethylene and a C ₁ -C ₆ alkyl (meth) acrylate or of a carboxylic acid vinyl ester saturated with

a copolymer of ethylene and an unsaturated epoxide, preferably glycidyl (meth) acrylate, and optionally a (C 1 -C 5) alkyl (meth) acrylate or a carboxylic acid vinyl ester; saturated. Another example of mixing is that:

a copolymer of ethylene and a C ₁ -C ₆ alkyl (meth) acrylate or of a carboxylic acid vinyl ester saturated with a copolymer of ethylene and a dicarboxylic anhydride; unsaturated acid, preferably maleic anhydride, and optionally a C 1 -C 5 alkyl (meth) acrylate or a saturated carboxylic acid vinyl ester.

additives

Each layer can also contain additives such as antioxidants, dyes or pigments, plasticizers, lubricants, solid fillers (talc, silica, kaolin, mica, ...), anti-oxygen, ... The charge can also be a black of carbon.

Fireproof additives

Each layer may also include at least one flame retardant additive. For 100 parts of thermoplastic polymer (s) a layer, the proportion of flame retardant additive is between 0 and 200 parts. Preferably, the flame retardant additive is incorporated in the layers L ₁ and L ₂ , or in the layer L ₁ , since the other layers L 3, L 4, L 3 and L'4 comprise a fluorinated polymer which has a good natural resistance. fire.

The flame retardant additive may be, for example, a halogenated derivative, a metal hydroxide, in particular magnesium or aluminum hydroxide, an antimony derivative, calcium carbonate or calcium tungstate. A commercial example of flame retardant agent is MARTINAL OL-107 sold by the company ALBERMARLE. The insulating multilayer structure in its form the ^era According to the form ^era, the insulating multilayer structure comprises disposed one against the other in the order indicated: • a layer L ₁ comprising: a) at least one polyolefin; b) or at least one functionalized polyolefin; c) or a mixture of both;

An L 2 layer of adhesion binder; • a layer L3 comprising at least one fluoropolymer grafted by irradiation, optionally in admixture with at least one fluoropolymer;

Optionally a layer L4 comprising at least one fluoropolymer, the layer L ₁ being the inner layer.

the Li layer

The polyolefin of the L ₁ layer is advantageously a polyethylene, preferably LDPE or PEMD.

The functionalized polyolefin is advantageously a copolymer of ethylene and at least one C ₁ -C ₅ alkyl (meth) acrylate or at least one saturated carboxylic acid vinyl ester. For example, it may be a copolymer of ethylene and methyl (meth) acrylate, ethyl or butyl, or a copolymer of ethylene and vinyl acetate.

It can also be a copolymer of ethylene, and:

an unsaturated epoxide, advantageously glycidyl (meth) acrylate, or an unsaturated acid anhydride, advantageously maleic anhydride, and optionally at least one C ₁ -C ₅ alkyl (meth) acrylate.

The comonomer (s) content of the ethylene is between 0.1 and 40% by weight, preferably between 1 and 35%. It can also be a mixture of several functionalized polyolefins. For example, it can be a mixture:

At least one copolymer of ethylene and at least one C 1 -C 5 alkyl (meth) acrylate or at least one saturated carboxylic acid vinyl ester, and

At least one copolymer of ethylene, and

an unsaturated epoxide, advantageously glycidyl (meth) acrylate, or an unsaturated acid anhydride, advantageously maleic anhydride, and optionally at least one alkyl (meth) acrylate, cs.

The layer L ₁ may also comprise a mixture of at least one polyolefin and at least one functionalized polyolefin with which it is compatible. When the polyolefin is a polyethylene, the functionalized polyolefin is thus preferably a copolymer of ethylene. Preferably, the mixture comprises from 0.1 to 99.9%, preferably from 1 to 99%, by weight of polyolefin to 99.9 to 0.1%, preferably from 99 to 1%, of functionalized polyolefin.

In order to have good mechanical strength, the melt flow rate of the polyolefin and / or the functionalized polyolefin, measured under the standard conditions (190 ^° C., load of 2.16 kg) of the ASTM D-1238 standard, is advantageously between 1 and 10, preferably between 1 and 5. The L2 layer

The L2 layer serves to promote the adhesion between the Li layer and the L3 layer. The adhesion is considerably enhanced if the unsaturated monomer which is grafted has one or more chemical function (s) capable of reacting with the chemical functions of the adhesion binder L2. For example, if an unsaturated monomer which comprises an acid anhydride functional group has been grafted, the adhesion binder may comprise epoxide or hydroxy functional groups. In the same way, if an unsaturated monomer which comprises an epoxide or hydroxy function has been grafted, the adhesion binder may comprise acid anhydride functions.

Advantageously, the L 2 adhesion binder comprises at least one functionalized polyolefin.

Preferably, in order to enhance the adhesion, the Li layer comprises at least one functionalized polyolefin (alone or in a mixture) which comprises chemical functions which react with those of the L 2 adhesion binder. For example, if the adhesion binder comprises acid anhydride functions, the functionalized polyolefin of Li may comprise epoxide or hydroxy functions. In the same way, if the adhesion binder comprises epoxide or hydroxyl functions, the functionalized polyolefin of Li may comprise acid anhydride functions.

The functionalized polyolefin of Li and L2 may be a copolymer of ethylene and

an unsaturated epoxide, advantageously glycidyl (meth) acrylate, or an unsaturated acid anhydride, advantageously maleic anhydride, and optionally at least one alkyl (meth) acrylate, cs. The advantage of glycidyl (meth) acrylate or maleic anhydride is their reactivity.

The functionalized polyolefin of L 2 can be used alone or optionally mixed with a polyolefin with which it is compatible. The mixture preferably comprises, by weight, from 0.1 to 99.9%, advantageously from 1 to 99%, preferably from 10 to 90%, even more preferentially from 50 to 90% of at least one functionalized polyolefin, for respectively from 99.9 to 0.1%, advantageously from 99 to 1%, preferably from 90 to 10%, even more preferably from 10 to 50% of at least one polyolefin. An example of such a mixture comprises a polyethylene, preferably a LDPE or a PDEM, and a copolymer of ethylene and

an unsaturated epoxide, advantageously glycidyl (meth) acrylate, or

an unsaturated acid anhydride, advantageously maleic anhydride, and optionally at least one C ₁ -C ₅ alkyl (meth) acrylate.

the L3 layer

The fluoropolymer grafted by irradiation of L3 can be used alone or optionally mixed with a fluoropolymer with which it is compatible (not modified by radiation grafting). The mixture preferably comprises, by weight, from 0.1 to 99.9%, advantageously from 1 to 99%, preferably from 10 to 90%, even more preferentially from 50 to 90% of irradiation-grafted fluoropolymer for 99 respectively. , 9 to 0.1%, advantageously from 99 to 1%, preferably from 90 to 10%, more preferably from 10 to 50% of fluorinated polymer (not modified by grafting). Advantageously, the fluoropolymer grafted by irradiation and the fluoropolymer are compatible, for example being of the same nature. For example, it may be a PVDF, homo- or copolymer, grafted by irradiation and unmodified PVDF, homo- or copolymer.

the IU layer The fluoropolymer of the L ₄ layer is a fluorinated polymer, preferably a PVDF, homo- or copolymer.

According to one preferred form, the insulating multilayer structure comprises arranged against each other in the order indicated: a layer L ₁ comprising: a) at least one polyethylene; b) and / or at least one copolymer of ethylene and at least one C ₁ -C ₅ alkyl (meth) acrylate or at least one saturated carboxylic acid vinyl ester; c) and / or at least one copolymer of ethylene, and

an unsaturated epoxide, advantageously glycidyl (meth) acrylate, or

an unsaturated acid anhydride, advantageously maleic anhydride, and optionally at least one alkyl (meth) acrylate,

cs

An L 2 layer of adhesion binder;

A layer L3 comprising at least one PVDF onto which at least one unsaturated monomer has been grafted by irradiation, optionally mixed with at least one PVDF;

Optionally, a layer L4 comprising at least one PVDF, the layer Li being the inner layer.

Examples 1 and 3 illustrate the preferred form of the ^era form of the invention. The layer L1 indeed comprises a polyethylene

CLEARFLEX, a copolymer of ethylene and a vinyl ester of acid saturated carboxylic acid (the EVATANE copolymer) and a copolymer of ethylene, a butyl acrylate and maleic anhydride.

The insulating multilayer structure in the 2 ^nd form According to a ^2nd shape, the insulating multilayer structure comprises, placed against one another in the order listed:

A layer L'i comprising: a) at least one functionalized polyolefin P ₁ which comprises chemical functions which react with the unsaturated monomer grafted on the fluoropolymer grafted with L'2, b) and optionally at least one polyolefin c) and / or optionally another functionalized polyolefin P2;

A layer L'2 comprising at least one fluoropolymer on which has been grafted by irradiation at least one unsaturated monomer, optionally mixed with at least one fluorinated polymer;

Optionally a layer L '3 comprising at least one fluorinated polymer, the layer L'i being the inner layer.

the IA layer

For there to be good adhesion between L'i and L'2, the layer L'i must comprise a functionalised polyolefin P ₁ which comprises chemical functions which react with the unsaturated monomer grafted on the fluoropolymer grafted with L '. 2. For example, if an unsaturated monomer which comprises an acid anhydride functional group has been grafted, the functionalized polyolefin may comprise epoxide or hydroxy functional groups. In the same way, if an unsaturated monomer which comprises an epoxide or hydroxy function has been grafted, the functionalized polyolefin may comprise acid anhydride functions. Advantageously, the functionalized polyolefin Pi is a copolymer of ethylene, and:

The i may also comprise a polyolefin and / or another functionalized polyolefin P2. The optional polyolefin is advantageously LDPE or DMEP.

To have a good mechanical strength, the melt index of the functionalised polyolefins Pi and P2 or the optional polyolefin, measured under standard conditions (190 ⁰ C, load of 2.16 kg) of ASTM D 1238, is advantageously between 1 and 10, preferably between 1 and 5.

The layer 2 The irradiated fluoropolymer by irradiation of the layer L'2 may be used alone or optionally mixed with a fluoropolymer with which it is compatible (not modified by radiation grafting). The mixture preferably comprises, by weight, from 0.1 to 99.9%, advantageously from 1 to 99%, preferably from 10 to 90%, even more preferentially from 50 to 90% of irradiation-grafted fluoropolymer for 99 respectively. , 9 to 0.1%, advantageously from 99 to 1%, preferably from 90 to 10%, more preferably from 10 to 50% of fluorinated polymer (not modified by grafting). Advantageously, the graft-modified fluoropolymer and the unmodified radiation-grafted polymer are compatible, for example by being of the same kind. For example, it may be a PVDF, homo- or copolymer, modified by radiation grafting and unmodified PVDF, homo- or copolymer.

The fluorinated polymer of the layer L'3 is a fluorinated polymer, preferably a PVDF, homo- or copolymer.

According to a preferred form, the insulating multilayer structure comprises arranged against each other in the indicated order: a layer L'i comprising: a) at least one copolymer of ethylene and

an unsaturated epoxide, advantageously glycidyl (meth) acrylate, or an unsaturated acid anhydride, advantageously maleic anhydride, and optionally at least one (C 1 -C 4) alkyl (meth) acrylate; ₈ , chosen so that its chemical functions react react with the unsaturated monomer grafted on the fluoropolymer grafted with L'2, b) and optionally at least one polyethylene, c) and / or optionally a copolymer of ethylene and at least one (C 1 -C 8) alkyl (meth) acrylate or at least one saturated carboxylic acid vinyl ester; An L 2 layer comprising at least one PVDF onto which at least one unsaturated monomer has been grafted by irradiation, optionally mixed with at least one PVDF; Possibly an Layer 3 comprising at least one PVDF, the layer L'i being the inner layer. For example, an ethylene comonomer will be an unsaturated epoxide when the grafted unsaturated monomer comprises an acid anhydride functional group. Likewise, an unsaturated acid anhydride will be selected when the grafted unsaturated monomer comprises an epoxide or hydroxy function.

The insulating multilayer structure in 3 ^rd form

According to a 3 ^rd form, the multilayer structure comprises, in order from the inside to the outside: • optionally, a layer L "i comprising

at least one polyolefin;

or at least one copolymer of ethylene and a C ₁ -C ₅ alkyl (meth) acrylate or of a saturated carboxylic acid vinyl ester; - or a mixture of both;

A layer V'2 comprising at least one functionalized polyolefin, optionally mixed with at least one polyolefin;

A layer L "3 comprising at least one fluorinated polymer on which has been grafted by irradiation at least one unsaturated monomer, optionally mixed with at least one fluorinated polymer, the V'3 layer being in direct contact with the V'2 layer; , '

Optionally a layer IA comprising at least one fluorinated polymer.

The adhesion is considerably enhanced if the unsaturated monomer which is grafted has one or more chemical function (s) capable (s) of reacting with the chemical functions of the functionalized polyolefin of the V'2 layer. It is preferably a copolymer of ethylene, and: an unsaturated epoxide, advantageously glycidyl (meth) acrylate, or

an unsaturated acid anhydride, advantageously maleic anhydride, and optionally at least one (C 1 -C 6) alkyl (meth) acrylate.

Preferably, the polyolefin of L "i and L" 2 is a polyethylene, advantageously a LDPE or a PEMD, and the fluoropolymer of L'3 and L'4 is a PVDF. Preferably, the layers are all arranged against each other.

The multilayer structures previously described are prepared by the coextrusion technique. The mixtures of polymers or polymers and additives are made using any mixing tool usually used in the thermoplastics industry, such as an extruder.

advantages of the insulating multilayer structure

The insulating multilayer structure has a function of mechanical, chemical and / or electrical protection of the cable. The term "insulation" is therefore to be taken in the broadest sense, and refers to a mechanical, chemical and / or electrical insulation.

The thickness of the inner layer (i.e. Li, L'or L "i) preferably represents at least 60% of the total thickness of the multilayer structure.

The multilayer structure of the invention does not require irradiation to adhere the different layers together. In addition, since the outermost layers (eg L3, L4, L2, L3, L3, L4) comprise a fluoropolymer, this improves the thermal resistance of the cable and this strengthens the fireproofing of the cable. it also improves its chemical resistance (for example, when the cable is in contact with solvents or an oily atmosphere) and prevents the swelling of the inner layer.

About the electric cable

The invention also relates to an electrical cable comprising at least one electrical conductor isolated by the insulating multilayer structure of the invention (that is to say that the inner layer Li, L'i or L "i is the most close to the electrical conductor).

The electric cables of the present invention can be used in energy transport and / or in information transmission. The electric current flowing can be high, medium or low voltage. The electrical cables of the invention can be used for example as electric cables in motor vehicles, boats, aircraft, in buildings or as power transmission cables (high voltage). They can also be used to carry high frequency, telephone and / or tele-computer and video signals (voice, data, images).

About the fiber optic cable

The invention also relates to an optical fiber cable comprising at least one transmission optical unit isolated by the insulating multilayer structure of the invention (that is to say that the inner layer Li, L'or L " i is the closest to the optical transmission unit).

Optical cables typically include an outer cable sheath surrounding optical transmission units. These optical units, also called compact tubes, consist mainly of tubes containing a plurality of optical fibers. Reference may be made to the following documents: EP 1382641 A1, EP 1160607 A1, EP 0937270 B1. The fiber optic cables of the present invention can be used in the transmission of information.

[Figures]

In the accompanying figures, the layer thicknesses have been deliberately disproportionate to reality for a better understanding. All figures correspond to sectional views.

FIG. 1 represents an electric cable 1. This comprises a conductive wire 2 isolated by a bilayer structure with a layer 3 (corresponding to L'i) and a layer 4 (corresponding to L'2).

FIG. 2 represents an electric cable 6. This comprises a conductor wire 2 isolated by a four-layer structure which comprises a layer 5 (corresponding to an L ₁ ), a layer 3 (corresponding to L 2), a layer 4 ( corresponding to L3) and a layer 7 (corresponding to L4).

FIG. 3 represents an electrical cable 8. This comprises a series of conductive wires 9 joined together and isolated by a bilayer structure with a layer 3 (corresponding to L'i) and a layer 4 (corresponding to V ₂ ).

FIG. 4 represents an electric cable 10. This comprises a series of conductive wires 9 joined and isolated by a four-layer structure which comprises a layer 5 (corresponding to L ₁ ), a layer 3 (corresponding to L 2), a layer 4 (corresponding to L3) and a layer 7 (corresponding to L4).

[Examples]

The following polymers were used: PVDF A: mixture of 70% KYNAR ^® 720 and 30% KYNAR® 720 on which has been grafted by irradiation 1% maleic anhydride, MVI (MEIT Volume index or melt volume index in the molten state ) 7 cm ^3/10 min (230 ⁰ C, 5 kg).

PVDF B: mixture of 70% of KYNARFLEX ^© 2850 and 30% KYNAR ^® 720 on which has been grafted by irradiation 1% maleic anhydride, MVI (MEIT Volume index or melt volume index in the molten state ) 7 cm ^3/10 min (230 ⁰ C, 5 kg).

Irradiation of the KYNAR ^® 720 is formed by first mixing the KYNAR ^® 720 (homopolymer with a melt index in volume melt of 10 cm ^3/10 min at 230 ⁰ C under 5 kg) and 2% by weight of maleic anhydride. The mixture is prepared using a twin-screw extruder at 230 ^° C. and 150 rpm at a flow rate of 10 kg / h. After the extrusion step, 1.8% of maleic anhydride remains in the product, the remainder being lost during the extrusion step. The product thus prepared and bagged in sealed aluminum bags. These bags are then irradiated under 3 Mrad. The PVDF grafted with maleic anhydride is then placed under vacuum overnight at 130 ^° C. to evacuate residual maleic anhydride and hydrofluoric acid released during irradiation. The content of maleic anhydride grafted is 1% by weight.

Lotader ^® AX8840: copolymer of ethylene and glycidyl methacrylate from Arkema and MVI (MEIT Volume index or melt flow rate in volume melt) 5 cm ^3/10 min (190 ⁰ C, 2, 16 kg). It contains 92% ethylene and 8% glycidyl methacrylate by weight.

LOTADER ^® 3210: terpolymer of ethylene, butyl acrylate and maleic anhydride from the company ARKEMA of melt-index 5 g / 10 min (190 ^° C., 2, 16 kg). It contains 3% by weight of maleic anhydride. EVATANE ^® 2805: copolymer of ethylene and vinyl acetate (28%) melt-index 6 g / 10 min (190 ⁰ C, 2, 16 kg).

MARTINAL ^® OL-107: flame retardant sold by the company ALBERMARLE. This is a precipitated aluminum hydroxide with the following characteristics: BET surface area = 6-8 m ² / g, oil absorption of 40-55 cm ³ / 100g, DOP absorption = 60-70 cm ^3/100 g, density 2.4 g / cm ^3, average particle diameter dso 0.9-1.5 .mu.m.

CLEARFLEX ^® FFDO: polyethylene sold by POLIMERI EUROPA density of 0.900 (23 ° C, ASTM D 1505) and a melt index 0.8 g / 10 min (190 ⁰ C, 2, 16 kg).

SANTONOX ^® R: antioxidant marketed by MONSANTO

EXAMPLE 1 (according to the preferred form of the ^era form of the invention) A cable is made by coextrusion on a copper wire (1 mm diameter) with a layer of an insulating composition containing 60% by weight of MARTINAL ^® OL 107, 9.75% CLEARFLEX ^® FFDO, 12% LOTADER ^® 3210, 18% EVATANE ^® 2805 and 0.25% SANTONOX R (1 mm thick), on which is coextruded a layer of LOTADER ^® AX8840 (50 μm thick), on which is coextruded a layer of PVDF A (200 μm thick).

The multilayer structure is therefore of the type: Li inner layer: CLEARFLEX ^® + thermoplastic polymers

LOTADER ^® 3210 + EVATANE ^® 2805 + flame retardant + antioxidant; L ₂ layer of adhesion binder: LOTADER ^® AX8840 L3 layer of PVDF A: mixture of irradiation grafted PVDF and PVDF The adhesion obtained between the different layers is good and greater than 25 N / cm. The elongation at break of this cable is 125% and the breaking stress is 18 MPa. Aging in the IRM902 oil is carried out at 90 ^° C. for 4 hours. The elongation at break measured after contact with the oil is 124% and the breaking stress is 19 MPa.

Example 2 (Comparative) A cable is made by coextrusion on a copper wire (1 mm diameter) of a single layer of the preceding insulating composition (1 mm thick). The elongation at break of this cable is 140% and the breaking stress is 12 MPa. Aging in the IRM902 oil is carried out at 90 ^° C. for 4 hours. The measured elongation at break is 131% and the breaking stress is 7.5 MPa.

Example 3: (according to the preferred form of the first ^embodiment of the invention) A cable is made by coextrusion on a copper wire (1 mm diameter) of a layer the previous insulating composition (1 mm thick) ), on which is co-extruded a layer of Lotad ER ^® AX8840 (50 microns thick), on which is coextruded a PVDF layer B (200 microns thick). The adhesion obtained between the different layers is good and greater than 25 N / cm. The elongation at break of this cable is 135% and the breaking stress is 15 MPa. Aging in the IRM902 oil is carried out at 90 ^° C. for 4 hours. The measured elongation at break is 134% and the breaking stress is 14.5 MPa. Table I

IU

insulating composition: 60% Martinal OL 107, 9.75% Clearflex FFDO, 12% Lotader 3210, 18% VA 2805 and 0.25% SANTONOX R

Claims

claims

1. Use of an insulating multilayer structure comprising arranged against each other in the order indicated: an inner layer L ₁ comprising: a) at least one polyolefin; b) or at least one functionalized polyolefin; c) or a mixture of both;

An L 2 layer of adhesion binder; • a layer L3 comprising at least one fluoropolymer on which has been grafted by irradiation at least one unsaturated monomer, optionally in admixture with at least one fluorinated polymer;

Optionally an L ₄ layer comprising at least one fluorinated polymer, for isolating an electrical and / or optical cable.

2. Use according to claim 1 characterized in that the functionalized polyolefin of Li is a copolymer of ethylene and at least one alkyl (meth) acrylate Ci-Cs or at least one vinyl ester d saturated carboxylic acid;

And / or a copolymer of ethylene and

an unsaturated epoxide, advantageously glycidyl (meth) acrylate, or

an unsaturated acid anhydride, advantageously maleic anhydride, and optionally at least one C 1 -C ₈ alkyl (meth) acrylate.

3. Use according to claim 2 characterized in that the functionalized polyolefin of L ₁ comprises chemical functions which react with those of the adhesion binder L2.

4. Use of an insulating multilayer structure comprising arranged against each other in the indicated order:

An inner layer L ₁ comprising: a) at least one polyethylene, b) and / or at least one copolymer of ethylene and at least one C 1 -C 5 alkyl (meth) acrylate or at least one a vinyl ester of saturated carboxylic acid; c) and / or at least one copolymer of ethylene, and

an unsaturated epoxide, advantageously glycidyl (meth) acrylate, or an unsaturated acid anhydride, advantageously maleic anhydride, and optionally at least one C ₁ alkyl (meth) acrylate; - C ₈ ,

A layer L 2 of adhesion binder, a layer L 3 comprising at least one PVDF on which has been grafted by irradiation at least one unsaturated monomer, optionally mixed with at least one PVDF,

Optionally a layer L4 comprising at least one PVDF, for isolating an electrical and / or optical cable.

5. Use according to any one of the preceding claims characterized in that the unsaturated monomer grafted on the fluoropolymer reacts with the chemical functions of the adhesion binder of L2.

6. Use according to any one of the preceding claims characterized in that the adhesion binder of L2 comprises at least one functionalized polyolefin.

7. Use according to claim 6 characterized in that the polyolefin functionalized L2 is a copolymer of ethylene and

an unsaturated epoxide, advantageously glycidyl (meth) acrylate, or

8. Use according to claim 7 characterized in that the polyolefin functionalized L2 is used alone or in admixture with at least one polyolefin with which it is compatible.

9. Use according to claim 8 characterized in that the mixture comprises, by weight, from 0.1 to 99.9%, advantageously from 1 to 99%, preferably from 10 to 90%, even more preferably from 50 to 90% by weight. at least one functionalized polyolefin for 99.9 to 0.1%, preferably 99 to 1%, preferably 90 to 10%, more preferably 10 to 50% of at least one polyolefin.

10. Use of an insulating multilayer structure comprising arranged against each other in the indicated order:

An internal layer L'i comprising: a) at least one functionalized polyolefin P ₁ which comprises chemical functions which react with the unsaturated monomer grafted on the fluoropolymer grafted with L'2, b) and optionally at least one polyolefin, c ) and / or optionally another functionalized polyolefin P2; A layer L'2 comprising at least one fluoropolymer on which has been grafted by irradiation at least one unsaturated monomer, optionally mixed with at least one fluorinated polymer; Optionally an Layer 3 comprising at least one fluorinated polymer, for isolating an electrical and / or optical cable.

11. Use according to claim 10 characterized in that the functionalized polyolefin P ₁ is a copolymer of ethylene and:

an unsaturated epoxide, advantageously glycidyl (meth) acrylate, or

12. Use of an insulating multilayer structure comprising arranged against each other in the indicated order:

An inner layer comprising: a) at least one copolymer of ethylene and

an unsaturated epoxide, advantageously glycidyl (meth) acrylate, or an unsaturated acid anhydride, advantageously maleic anhydride, and optionally at least one C ₁ - alkyl (meth) acrylate;

C ₈ , chosen so that its chemical functions react react with the unsaturated monomer grafted on the fluoropolymer grafted with L'2, b) and optionally at least one polyethylene, c) and / or optionally a copolymer of ethylene and at least one (C 1 -C 8) alkyl (meth) acrylate or at least one saturated carboxylic acid vinyl ester;

A layer IΛ comprising at least one PVDF onto which at least one unsaturated monomer has been grafted by irradiation, optionally mixed with at least one PVDF;

Optionally an Layer 3 comprising at least one PVDF, for isolating an electrical and / or optical cable.

13. Use of an insulating multilayer structure comprising in order from inside to outside:

Optionally, a layer L "comprising at least one polyolefin; or at least one copolymer of ethylene and one

C1-C8 alkyl (meth) acrylate or a saturated carboxylic acid vinyl ester; - or a mixture of both;

A layer L "3 comprising at least one fluoropolymer on which has been grafted by irradiation at least one unsaturated monomer, optionally mixed with at least one fluorinated polymer, the L" 3 layer being directly in contact with the V'2 layer ;

• optionally, a layer L ^'J 4 comprising at least one fluoropolymer.

14. Use according to claim 13 characterized in that the unsaturated monomer which is grafted has one or more function (s) chemical (s) likely to react with the chemical functions of the functionalized polyolefin of the L "2 layer.

15. Use according to one of claims 13 or 14 characterized in that the functionalized polyolefin is a copolymer of ethylene, and:

an unsaturated epoxide, advantageously glycidyl (meth) acrylate, or

16. Use according to one of claims 13 to 15 characterized in that the polyolefin V \ and L "2 is a polyethylene.

17. Use according to any one of claims 1 to 3, 5 to 11 or 13 to 16 characterized in that the fluoropolymer on which is grafted unsaturated monomer layers L3, L'2 or L "3 or the polymer unmodified fluorinated layer L3, L4, L'2, L'3, L "3 or L" 4 is prepared by polymerization of one or more monomers of formula (I):

\ J> \ / ^X2 (!)

^F X3 in which:

• Xi is H or F;

X 2 and X 3 denote H, F, Cl, a fluorinated alkyl group of formula C _n FmHp- or a fluorinated alkoxy group C _n FmHpO-, n being an integer between 1 and 10, m an integer between 1 and (2n + l), p being 2n + lm.

18. Use according to claim 17 characterized in that the fluoropolymer is a PVDF homopolymer or a VDF-HFP copolymer containing at least 50% by weight of VDF, preferably at least 75% by weight of VDF and preferably at least 85%. by weight of VDF.

19. Use according to any one of the preceding claims characterized in that the unsaturated monomer which is grafted by irradiation on the fluoropolymer has a C = C double bond and at least one polar function which may be a function:

carboxylic acid, carboxylic acid salt,

- carboxylic acid anhydride,

epoxide, carboxylic acid ester, silyl.

- carboxylic amide,

- hydroxy,

isocyanate.

20. Use according to claim 19 characterized in that the unsaturated monomer is an unsaturated carboxylic acid or a functional unsaturated carboxylic acid derivative having 4 to 10 carbon atoms.

21. Use according to claim 19 characterized in that the unsaturated monomer is selected from methacrylic acid, acrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, acid undecylenic acid, allylsuccinic acid, cyclohex-4-ene-1,2-dicarboxylic acid, 4-methyl-cyclohex-4-ene-1,2-dicarboxylic acid, bicyclo 1) hept-5-ene-2,3-dicarboxylic acid, x-methylbicyclo [2,2,1-hept-5-ene-2,3-dicarboxylic acid, zinc, calcium or sodium undecylenate, maleic anhydride, itaconic anhydride, citraconic anhydride, dichloromaleic anhydride, difluoromaleic anhydride, itaconic anhydride, crotonic anhydride, acrylate or glycidyl methacrylate, allyl glycidyl ether, vinyl silanes such as vinyl trimethylsilane, vinyl triethoxysilane, vinyl triacetoxysilane, gamma-methacryloxypropyltrimethoxysilane.

22. Use according to any one of the preceding claims characterized in that each layer may comprise from 0 to 100 parts of at least one flame retardant additive per 100 parts of thermoplastic polymer (s) comprising said layer.

23. An electrical cable comprising at least one electrical conductor insulated by an insulating multilayer structure as defined in any one of claims 1 to 22.

24. An optical cable comprising at least one optical transmission unit isolated by an insulating multilayer structure as defined in any one of claims 1 to 22.