CA2412133A1 - Polyamide and evoh-based multilayered conductor pipe for the transport of gasoline - Google Patents

Abstract

The invention relates to a multilayer tube successively comprising in a radial direction from the outside to the inside: an outer layer formed from a polyamide chosen from poly (undecanoamide) and polylauryllactam; a layer formed of a binder; a layer formed from an ethylene-vinyl alcohol copolymer; a layer formed from a mixture of polyamide and polyolefin with a polyamide matrix; a layer formed of a lian t; and an inner layer formed from a polyamide selected from poly (undécanoamide) and polylauryllactam and having a filler dispersed ed of an electrically producing a surface resistivity less than 10 6 .Omega .. These layers each have a contact zone and adhere to each other in the respective contact area. The tube of the present invention is very low permeability to petrol particularly to hydrocarbons and to their additives, particularly alcohols or ethers. This tube also has good resistance to motor fuels and lubricating oils. It also has very good mechanical properties at low or high temperatures.

Description

CONDUCTIVE MULTI-LAYER TUBE BASED ON POLYAMIDES
AND EVOH FOR THE TRANSPORT OF GASOLINE
The present invention relates to conductive tubes based on polyamides and ethylene-vinyl alcohol copolymer (EVOH) for the transport of petrol and in particular to bring petrol from the tank of a automobile to engine.
For safety and environmental reasons, the automobile manufacturers impose on these tubes both characteristics mechanical such as burst strength and flexibility with good cold shock resistance (-40 ° C) as well as high temperature (125 ° C), and also very low permeability to hydrocarbons and their additives, in especially alcohols like methanol and fethanol. These tubes should also have good resistance to motor fuels and lubricating oils.
In motor vehicles, under the effect of the injection pump, gasoline travels at high speed in the pipes connecting the engine to the tank.
In some cases, the gasoline / internal wall friction of the tube can generate of the electrostatic charges, the accumulation of which can lead to a discharge electric (spark) capable of igniting gasoline with consequences catastrophic (explosion). Also, is it necessary to make the inner surface of the tube in contact with gasoline. These tubes are made by coextrusion of the different layers according to the usual techniques of thermoplastics.
Among the characteristics of the specifications of these tubes, five are particularly difficult to obtain jointly in a simple manner - cold shock resistance (-40 ° C), the tube does not break,

2 - resistance to fuels, - resistance to high temperature (125 ° C), - very low permeability to petrol, - good dimensional stability of the tube when used with S the essence.
In multilayer pipes of various structures, the shock resistance to cold remains unpredictable before performing standardized resistance tests to the cold shock.
Furthermore, it is already known from the European patent application No. 781.799 that in motor vehicles, under the effect of the injection, gasoline circulates at high speed in the pipes connecting the engine to tank. In some cases, the gasoline / internal wall friction of tube can generate electrostatic charges, the accumulation of which can lead to an electric shock (spark) capable of igniting petrol with catastrophic consequences (explosion). Also, is it necessary to limit the surface resistivity of the internal face of the tube to a value in general less than 106 ohms. It is known to lower resistivity superficial resins or polymeric materials by incorporating materials therein conductors and / or semiconductors such as carbon black, fibers steel, carbon fibers, particles (fibers, plates, spheres) metallized with gold, silver or nickel.
Among these materials, carbon black is more particularly employee, for economic reasons and ease of implementation. In apart from its particular electroconductive properties, carbon black himself contains a filler such as, for example, talc, chalk, kaolin.
Thus, those skilled in the art know that when the charge rate increases, the viscosity

3 of the polymer / filler mixture increases. Likewise, when the charge rate increases, the flexural modulus of the charged polymer increases. These known and predictable phenomena are explained in "Handbook of Fillers and Reinforcements for Plastics "edited by HS Katz and JV Milewski - Van Nostrand Reinhold Company - ISBN 0-442-25372-9, see in particular the Chapter 2, Section II for charges in general and Chapter 16, Section VI
for carbon black in particular.
As for the electrical properties of carbon black, the bulletin technique "Ketjenblack EC - BLACK 94/01" from AKZO NOBEL
indicates that the resistivity of the formulation drops very suddenly when a critical level of carbon black, called the percolation threshold, is reached.
When the carbon black rate increases further, the resistivity decreases rapidly until reaching a stable level (plateau area). We therefore prefer, for a given resin, operate in the plateau area, where a dosage error will not that a weak influence on the resistivity of the compound.
Also known from European patent application No. 731,308 are polyamide and EVOH-based tubes for the transport of petrol. These tubes may have a 4-layer structure comprising respectively one layer outer of polylauryllactam (PA-12), a binder layer which is a grafted polyolefin, a layer of EVOH and an inner layer in contact with petrol comprising a blend of polyamide and matrix polyolefin polyamide.
European patent No. 428.833 describes a three-layer tube comprising respectively an outer layer of PA-12, a layer of binder which is a grafted polyolefin and an inner layer of EVOH
contact with gasoline.

4 European patents Nos. 428.834 and 477.606 describe a tube with five layers respectively comprising an outer layer of PA-12, a layer of binder which is a grafted polyolefin, a layer of polycapronamide (PA-6), a layer of EVOH and an inner layer of PA-6 in contact with gasoline.
U.S. Patent No. 5,038,833 describes a three-layer tube comprising respectively an outer layer of PA-12, a layer EVOH and an inner layer of PA-12 in contact with petrol.
All these tubes have good properties, but the thickness of the layers of binder is not easy to control and it may result in delaminations.
In the tube described in US Patent No. 5,038,833, there is no binder but he delaminations occur.
European patent No. 1,036,967 describes a multilayer tube based on polyamides, characterized in that it comprises in its radial direction of inside to outside - an inner layer formed of a polyamide or a mixture of polyamide and polyolefin with a polyamide matrix, this layer comprising a dispersed charge of electroconductive carbon black producing resistivity surface area less than 106 S2, - an intermediate layer formed of a polyamide or a mixture of polyamide and polyolefin with a polyamide matrix, this layer not comprising no carbon black electrically conductive or quantity significant of this carbon black, - a layer of EVOH, - a layer of binder, and - an outer layer of polyamide, the above layers adhering to each other in their contact area respectively.
The multilayer tube described in European Patent No. 1,036,967 has very good mechanical properties and gas tightness but we discovered

5 only if the inner conductive layer is based on poly (undecanoamide) (PA-11) or PA-12 and if the intermediate layer is based on a mixture of polyamide and polyolefin to polyamide matrix, so this is a very good compromise between conductivity and barrier properties of the tube. However, the adhesion between this conductive inner layer and the layer intermediate is not perfect. This imperfect adhesion does not affect resistance to shock cold which remains the most important mechanical criterion; however, in case the tube is in depression, then the inner layer peels off partially and risk of clogging the tube. It is therefore necessary to put a binder of coextrusion between these two layers.
The present invention relates to a multilayer tube comprising successively in a radial direction from outside to inside a first layer formed from a polyamide chosen from PA-11 and PA-12, the first layer defining an outer layer, - a second layer formed of a binder, - a third layer formed of EVOH, a fourth layer formed from a mixture of polyamide and polyolefin with polyamide matrix, a fifth layer formed of a binder, and a sixth inner layer formed from a polyamide chosen from PA-11 and PA-12 and comprising a dispersed charge of an electrically conductive

6 producing a surface resistivity less than 106 SZ, the sixth layer defining an inner layer, the first, second, third, fourth, fifth and sixth layers each having a contact zone and adhering to each other in their zone of S respective contact.
Advantageously, the tube according to the invention has the characteristics smvantes - an outside diameter ranging from 6 to 12 mm, a total thickness of 0.38mm to 2mm, - a thickness of 300 to 800 ~, m for the outer layer in polyamide 11 or 12, - a thickness of 10 to 100 ~ m for the binder layers, - a thickness of 10 to 200 ~ m for the EVOH layer, - a thickness of 25 to 500 ~ m for the layer formed of a mixture of 1 S polyamide and polyolefin with polyamide matrix, - a thickness of 25 to 300 ~, m for the inner polyamide layer charged with an electroconductive.
The tube of the present invention is very slightly permeable to petrol particularly hydrocarbons and their additives, in particular alcohols like methanol and ethanol or ethers like methyl-tert-butyl ether (MTBE) or ethyl-tert-butyl ether (ETBE). This tube also has a good resistance to motor fuels and lubricating oils. he present furthermore very good mechanical properties at low or high temperature.

7 Regarding the outer layer of PA-11 or PA-12, these polyamides advantageously have a number-average molecular mass Mn generally greater than or equal to 5000. Their inherent viscosity (measured at 20 ° C for a sample of 0.5 g in 100 g of meta-cresol) is in general greater than 0.7.
Advantageously, the polyamide of the outer layer is plasticized by common plasticizers such as n-butyl benzene sulfonamide (BBSA) and copolymers comprising polyamide blocks and polyether blocks.
The polyamide block and polyether block copolymers result from the copolycondensation of reactive end polyamide sequences with polyether sequences with reactive ends, such as, among others 1) polyamide sequences with diamine chain ends with sequences polyoxyalkylenes with dicarboxylic chain ends;
2) polyamide sequences containing dicarboxylic chain ends with polyoxyalkylene blocks with diamine chain ends obtained by cyanoethylation and hydrogenation of alpha-omega polyoxyalkylene sequences aliphatic dihydroxylates called polyetherdiols; and 3) polyamide sequences containing dicarboxylic chain ends with polyetherdiols, the products obtained being, in this particular case, polyetheresteramides. These copolymers are advantageously used.
Polyamide sequences with dicarboxylic chain ends come, for example, from the condensation of alpha-omega acids aminocarboxylic, lactams or dicarboxylic acids and diamines in presence of a chain limiting dicarboxylic acid.

8 The polyamide sequences with diamine chain ends originate, for example, condensation of alpha-omega aminocarboxylic acids, lactams or dicarboxylic acids and diamines in the presence of a diamine chain limiter.
The polyether may for example be a polyethylene glycol (PEG), a polypropylene glycol (PPG) or polytetramethylene glycol (PTMG). This the latter is also called polytetrahydrofuran (PTHF).
The molar mass in number M ~ of the polyamide sequences is included between 300 and 15,000, and preferably between 600 and 5,000. The mass M ~ of polyether blocks is between 100 and 6000, and preferably between and 3,000.
Polymers with polyamide blocks and polyether blocks can also understand patterns distributed randomly. These polymers can be prepared by the simultaneous reaction of polyether and block precursors polyamides.
For example, polyetherdiol, a lactam (or a alpha-omega amino acid) and a chain-limiting diacid in the presence of a little of water. A polymer is obtained which essentially has polyether blocks, polyamide blocks of very variable length, but also the different reagents having reacted randomly which are distributed statistically along of the polymer chain.
These polymers with polyamide blocks and polyether blocks that they come from of the copolycondensation of polyamide and polyether blocks prepared previously or in a one-step reaction have, for example, hardnesses shore D can be between 20 and 75, and advantageously between 30 and 70 and an inherent viscosity between 0.8 and 2.5 measured in metacresol at 250 °

9 C for an initial concentration of 0.8 g / 100 ml. The MFI of these polymers can be between 5 and 50 (235 ° C under a load of 1 kg). The term "MFI" is an abbreviation of "Melt Flow Index" and designates the fluidity index at the molten state.
Polyetherdiol blocks are either used as such and co-condensed with polyamide blocks with carboxylic ends, or they are aminated for be transformed into polyether diamines and condensed with polyamide blocks with carboxylic ends. They can also be mixed with polyamide precursors and a chain limiter to make polymers to polyamide blocks and polyether blocks having patterns distributed in such a way statistical.
Polymers with polyamide and polyether blocks are described in the US patents Nos. 4.331.786, 4.115.475, 4.195.015, 4.839.441, 4,864,014, 4,230,838 and 4,332,920.
The ratio of the quantity of copolymer with polyamide blocks and blocks polyether on the amount of polyamide is, by weight, advantageously included between 10/90 and 60 / 40. Mention may for example be made of the PA 6 block copolymer and PTMG blocks and the copolymer with PA-12 blocks and PTMG blocks.
With regard to the binder layers, this defines any product which allows good adhesion between the layers concerned, i.e. between the layer outer in PA-11 or PA-12 and the EVOH layer, and between the layer of mixture of polyamide and polyolefin with polyamide matrix and the layer interior in PA-11 or PA-12. The binder is advantageously chosen from among the functionalized polyolefins and copolyamides.
As examples of a binder based on functionalized polyolefins, we can quote - polyethylene, polypropylene, ethylene copolymers and of at least one alpha olefin, mixtures of these polymers, all of these polymers being grafted with anhydrides of unsaturated carboxylic acids such as, for example, maleic anhydride, or mixtures of these polymers 5 grafted and these non-grafted polymers;
- copolymers of ethylene with at least one product chosen from (i) unsaturated carboxylic acids, their salts, their esters, (ü) the esters vinyl of saturated carboxylic acids, (iii) dicarboxylic acids unsaturated, their salts, their esters, their hemiesters, their anhydrides, (iv) the

10 unsaturated epoxides; these copolymers can be grafted with anhydrides unsaturated dicarboxylic acids such as maleic anhydride or unsaturated epoxides such as glycidyl methacrylate.
As for the binders of the copolyamide type usable in the present invention, they have a melting temperature (Dorme DIN 53736B) included between 60 and 200 ° C and their relative viscosity in solution can be between 1.3 and 2.2 (Standard DIN 53727, solvent m-cresol, concentration 0.5 g / 100 ml, temperature 25 ° C, Ubbelohde viscometer). Their rheology in the state fade is preferably close to that of the materials of the outer layer and the inner layer.
Copolyamides come, for example, from the condensation of acids alpha-omega aminocarboxylic lactams or dicarboxylic acids and diamine.
According to a first preferred embodiment of the invention, the copolyamides used as binders result from the condensation of at least two alpha omega aminocarboxylic acids or at least two lactams having 6 to 12 carbon atoms or a lactam and an acid aminocarboxylic having not the same number of carbon atoms in

11 possible presence of a chain limiter which can for example be a monoamine or a diamine or a mono carboxylic acid or a diacid carboxylic acid. Among the chain limiters, there may be mentioned in particular the acid adipic, azelaic acid, stearic acid, dodecanediamine. Such copolyamides may also include units which are remnants of diamines and dicarboxylic acids.
As examples of dicarboxylic acid, mention may be made of adipic acid, nonanedioic acid, sebacic acid and dodecanedioic acid.
As examples of alpha omega aminocarboxylic acid, mention may be made aminocaproic acid, aminoundecanoic acid and acid aminododecanoic.
As examples of lactam, mention may be made of caprolactam and laurolactam (2-azacyclotridecanone).
According to a second preferred embodiment of the invention, the copolyamides used as binders result from the condensation of at least one alpha-omega aminocarboxylic acid (or a lactam), at least one diamine and at least one dicarboxylic acid. Alpha omega aminocarboxylic acid, the lactam and the dicarboxylic acid can be chosen from those mentioned more high.
The diamine can be a branched, linear or linear aliphatic diamine.
cyclic or even arylic.
As examples, mention may be made of hexamethylenediamine, piperazine, fisophorone diamine (IPD), methyl pentamethylenediamine (MPDM), bis (aminocyclohexyl) methane (BACM), bis (3-methyl-4 aminocyclohexyl) methane (BMACM).

12 As examples of copolyamide, the following may be cited a) Copolyamide 6/12 / IPD.6 in which 6 designates units resulting from the condensation of caprolactam, 12 designates units resulting from the condensation of laurolactam (2-azacyclotridecanone), and IPD.6 designates patterns resulting from the condensation of fisophorone diamine and adipic acid.
The proportions by weight are respectively 20/65/15.
The melting temperature is from 125 ° C to 135 ° C.
b) Copolyamide 6 / 6.6 / 12 in which:
6 designates units resulting from the condensation of caprolactam, 6-66 denotes hexamethyleneadipamide units (hexamethylene-diamine condensed with adipic acid), and 12 designates units resulting from the condensation of laurolactam (2-azacyclotridécanone).
The proportions by weight are 40/20/40 respectively.
The melting temperature is from 115 ° C to 127 ° C.
c) Copolyamide pip.l2 / pip.9 / 11 in which:

13 pip.l2 designates units resulting from the condensation of piperazine and C12 diacid, pip-99 denotes units resulting from the condensation of piperazine and C9 diacid, and 11 designates the patterns resulting from the condensation of the acid aminoundecanoic.
The proportions by weight are 35/35/30 respectively.
Copolyamide manufacturing processes are known in the art and these copolyamides can be manufactured by polycondensation, by example in an autoclave.
According to a third preferred embodiment of the invention, the copolyamides used as binders are a mixture of two copolyamides 6/12 resulting from the condensation of caprolactam with lauryllactam, of which one is rich in motifs derived from caprolactam and the other is rich in reasons derivatives of lauryllactam. As regards the mixture of copolyamides 6/12, one of the copolyamides comprises by weight more units derived from caprolactam than of motifs derived from lauryllactam and the other comprises by weight more than derived from lauryllactam only from motifs derived from caprolactam. Onne come out not within the scope of the invention if the caprolactam were replaced in whole or part by aminocaproic acid, as well as lauryllactam which can be replaced by aminododecanoic acid. These copolyamides can include other patterns provided the ratios of the proportions of patterns derived from caprolactam and from motifs derived from lauryllactam be respected.
Advantageously, the copolyamide rich in units derived from caprolactam comprises 60 to 90% by weight of units derived from caprolactam for respectively 40 to 10% by weight of units derived from lauryllactam.

14 Advantageously, the copolyamide rich in units derived from lauryllactame comprises 60 to 90% by weight of units derived from lauryllactame for respectively 40 to 10% by weight of units derived from caprolactam.
As for the proportions of copolyamide rich in units derived from caprolactam and copolyamide rich in motifs derived from lauryllactam them may be, by weight, from 40/60 to 60/40, and preferably 50/50.
These mixtures of copolyamides can also comprise up to 30 parts by weight of other (co) polyamides or grafted polyolefins per 100 parts of copolyamides rich in motifs derived from caprolactam and rich in motifs derived from lauryllactam.
These copolyamides have a melting temperature (Standard DIN 537368) between 60 and 200 ° C and their relative viscosity in solution can to be between 1.3 and 2.2 (Standard DIN 53727, solvent m-cresol, concentration 0.5 g / 100 ml, temperature 25 ° C, Ubbelohde viscometer). Their rheology at the molten state is preferably close to that of the materials of the layers adjacent. These products are manufactured by the usual techniques of polyamides. Processes are described in US patents Nos.
4,424,864, 4,483,975, 4,774,139, 5,459,230, 5,489,667, 5,750,232 and 5,254,641.
If the outer layer is PA-11, we prefer that the binder between this PA-11 layer and the EVOH layer is based on polyolefins functionalized. If the outer layer is PA-12, we prefer that the binder between this layer of PA-12 and the layer of EVOH is based on copolyamide.
It is the same for the binder between the inner layer and the layer of polyamide and polyolefin blend with polyamide matrix; if the diaper interior is in PA-11, the binder is preferably based on polyolefins functionalized and, if the inner layer is PA-12, the binder is preferably based on copolyamide.

As regards the layer formed of EVOH copolymer, it can be made up of EVOH or mixture based on EVOH. fEVOH is also called saponified ethylene-vinyl acetate copolymer. The ethylene copolymer saponified vinyl acetate to be used according to the present invention is a 5 copolymer having an ethylene content of 20 to 70 mol%, preferably from 25 to 70 mol%, the degree of saponification of its acetate component vinyl being not less than 95 mol%. With ethylene content less than 20 mol%, the barrier properties under conditions of strong humidity is not as high as would be desired, while a content in 10 ethylene exceeding 70 mol% leads to decreases in properties fence.
When the degree of saponification or hydrolysis is less than 95% in mol barrier properties are sacrificed.
By barrier properties is meant impermeability to gases, liquids and in particular oxygen, gasoline for cars.

Among these saponified copolymers, those which have melt flow indices hot in the range of 0.5 to 100 g / 10 minutes are particularly helpful.
Advantageously, the MFI is chosen between 5 and 30 (g / lOmin at 230 ° C under 2.16 kg).
It is understood that this saponified copolymer may contain small amounts proportions of other comonomeric ingredients, including α-olefins like propylene, fisobutene, fa-octene, a-dodecene, fa-octadecene, etc ..., unsaturated carboxylic acids or their salts, partial alkyl esters, of the complete alkyl esters, nitriles, amides and anhydrides of said acids, and unsaturated sulfonic acids or their salts.
As for the mixtures based on EVOH, they are such that fEVOH forms the matrix, i.e. fEVOH represents at least 40% by weight of the mixture and preferably at least 50%. The other constituents of the mixture are chosen

16 among polyolefins, polyamides and optionally polymers functional.
As a first example of mixtures based on EVOH, there may be mentioned compositions comprising - 55 to 99.5 parts by weight of EVOH copolymer, and - 0.5 to 45 parts by weight of polypropylene and compatibilizer, their proportions being such that the ratio of the quantity of polypropylene sure the amount of compatibilizer is between 1 and 5.
Advantageously, the report of the MFI of fEVOH to the MFI of polypropylene is greater than 5, and preferably between 5 and 25.
Advantageously, the polypropylene MFI is between 0.5 and 3 (in g / 10mm at 230 ° C under 2.16 kg). According to an advantageous form, the compatibilizer is a polyethylene carrying polyamide grafts and it results of reaction (i) of an ethylene copolymer and an unsaturated monomer X
grafted or copolymerized with (ü) a polyamide. The copolymer of (ethylene and of an grafted unsaturated monomer X is such that the monomer X is copolymerized and it can be chosen from ethylene-maleic anhydride copolymers and ethylene - (meth) acrylate - maleic anhydride copolymers, these copolymers comprise from 0.2 to 10% by weight of maleic anhydride and from 0 to 40% by weight of alkyl (meth) acrylate. According to another advantageous form, the compatibilizer is a polypropylene bearing polyamide grafts which results of reaction (i) of a propylene homopolymer or copolymer comprising an unsaturated monomer X, grafted or copolymerized, with (ü) a polyamide. Advantageously, the monomer X is grafted. The monomer X is advantageously an unsaturated carboxylic acid anhydride such that, for example example, malefic anhydride.

17 As a second example of mixtures based on EVOH, we can cite compositions including - 50 to 98% by weight of an EVOH copolymer, - 1 to 50% by weight of a polyethylene, and - 1 to 15% by weight of a compatibilizer consisting of a mixture of LLDPE or metallocene polyethylene and a polymer chosen from elastomers, very low density polyethylenes and polyethylenes metallocenes, the mixture being co-grafted with an unsaturated carboxylic acid or a functional derivative of this acid.
Advantageously, the compatibilizer is such that the MFIIO / MFIZ ratio is between 5 and 20, where MFIZ is (melt flow index at 190 ° C under a load of 2.16 kg, measured according to ASTM D 123 8, and MFI I
where is (melt flow index at 190 ° C under a load of 10 kg according to ASTM D1238.
As a third example of mixtures based on EVOH, there may be mentioned compositions comprising - 50 to 98% by weight of an EVOH copolymer, - 1 to 50% by weight of an ethylene - (meth) acrylate copolymer, and - 1 to 15% by weight of a compatibilizer resulting from reaction (i) of a copolymer of ethylene and of an unsaturated monomer X grafted or copolymerized with (ü) a copolyamide.
Advantageously, the copolymer of ethylene and of a monomer unsaturated X grafted or copolymerized is such that the monomer X is copolymerized and it is a copolymer of ethylene and maleic anhydride or a copolymer of ethylene, an alkyl (meth) acrylate and anhydride Maleficent. Advantageously, these copolymers comprise from 0.2 to 10% by weight of maleic anhydride and 0 to 40% by weight of alkyl (meth) acrylate.
As regards the layer formed from a mixture of polyamide and 5 polyolefin with a polyamide matrix, polyamide means the products of condensation - one or more amino acids, such as aminocaproic acids, amino-7-heptanoic, amino-11-undecanoic and amino-12-dodecanoic of a or several lactams such as caprolactam, oenantholactam and lauryllactam;
10 - one or more salts or mixtures of diamines such fhexamethylenediamine, dodecamethylenediamine, metaxylyenediamine, bis-p aminocyclohexylmethane and trimethylhexamethylene diamine with diacids such as isophthalic, terephthalic, adipic acids, azelaic, suberic, sebacic and dodecanedicarboxylic.
1 By way of examples of polyamide, mention may be made of PA-6 and polyhexamethyleneadipamide (PA-6,6).
Copolyamides can also be advantageously used. We can cite copolyamides resulting from the condensation of at least two alpha acids omega aminocarboxylic or two lactams or one lactam and one acid alpha omega aminocarboxylic. We can also cite copolyamides resulting from the condensation of at least one alpha omega acid aminocarboxylic (or lactam), at least one diamine and at least one acid dicarboxylic.
As examples of lactam, mention may be made of those having 3 to 12 atoms carbon on the main cycle and can be substituted. We can cite through example (3, (3-dimethylpropriolactam, a, a-dimethylpropriolactam, famylolactam, caprolactam, capryllactam and lauryllactam.
As examples of alpha omega aminocarboxylic acid, mention may be made amino undecanoic acid and aminododecanoic acid. As examples dicarboxylic acid, there may be mentioned adipic acid, sebacic acid, acid isophthalic, butanedioic acid, 1,4 cyclohexyldicarboxylic acid, terephthalic acid, the sodium or lithium salt of the acid sulphoisophthalic, dimerized fatty acids (these dimerized fatty acids have a dimer content of at least 98% and are preferably hydrogenated) and the acid dodecanedioic HOOC- (CH2) io-COOH.
The diamine can be an aliphatic diamine having from 6 to 12 atoms, it can be arylic and / or cyclic saturated. As examples, we can to quote hexamethylenediamine, piperazine, tetramethylene diamine, foctamethylene diamine, decamethylene diamine, dodecamethylene diamine, 1,5 diaminohexane, 2,2,4-trimethyl-1,6-diamino-hexane, polyols diamine, isophorone diamine (IPD), methyl pentamethylenediamine (MPDM), bis (aminocyclohexyl) methane (BACM), bis (3-methyl-4 aminocyclohexyl) methane (BMACM).
As examples of copolyamide, mention may be made of copolymers of caprolactam and lauryllactam (PA-6/12), copolymers of caprolactam, adipic acid and hexamethylene diamine (PA-6 / 6,6), copolymers of caprolactam, lauryllactam, adipic acid and hexamethylene diamine (PA-6/12 / 6.6), copolymers of caprolactam, lauryllactam, acid undecanoic amino 11, azelaic acid and hexamethylene diamine (PA-6 / 6,9 / 11/12), copolymers of caprolactam, lauryllactam, acid undecanoic amino 11, adipic acid and hexamethylene diamine (PA-6 / 6,6 / 11/12), copolymers of lauryllactam, azelaic acid and of hexamethylene diamine (PA-6.9 / 12).

Advantageously, the copolyamide is chosen from PA-6/12 and PA-6 / 6,6. The advantage of these copolyamides is their melting temperature lower than that of PA-6.
It is also possible to use any amorphous polyamide without melting point.
5 The MFI of polyamides and mixtures of polyamide and polyolefin of the present invention is measured according to the rules of the art at a temperature of 15 to 20 ° C above the melting point of the polyamide.
Regarding mixtures based on PA-6, the MFI is measured at 235 ° C. under 2.16 kg.
Concerning mixtures based on PA-6.6, the MFI is measured at 275 ° C. under 1 kg.
Polyamide blends can be used. Advantageously, the MFI
polyamides is between 1 and 50 g / 10 min.
We would not go beyond the scope of (invention by replacing part of the polyamide by a copolymer with polyamide blocks and polyether blocks, that is to say using a mixture comprising at least one of the preceding polyamides and At least one copolymer with polyamide blocks and polyether blocks. The copolymers polyamide blocks and polyether blocks have been described above.
As for the polyolefin of the mixture of polyamide and polyolefin forming the layer following that of EVOH, it can be functionalized or not functionalized or be a mixture of at least one functionalized and / or 20 minus one not functionalized. To simplify the text, this polyolefin East denoted by (B) and functionalized polyolefins have been described below (B 1) and non-functionalized polyolefins (B2).
A non-functionalized polyolefin (B2) is conventionally a homo polymer or copolymer of alpha olefins or diolefins, such as by example, ethylene, propylene, butene-1, octene-1, butadiene. As examples we can cite - homopolymers and copolymers of polyethylene, in particular LDPE, HDPE, LLDPE (linear low density polyethylene, or low polyethylene linear density), VLDPE (very low density polyethylene, or very low polyethylene low density) and metallocene polyethylene;
S - homopolymers or copolymers of propylene;
- ethylene / alpha-olefin copolymers such as ethylene / propylene, EPR (short for ethylene-propylene-rubber) and ethylene / propylene / diene (EPDM);
- styrene / ethylene-butene / styrene block copolymers (SEBS), styrene / butadiene / styrene (SBS), styrene / isoprene / styrene (SIS), styrene / ethylene-propylene / styrene (SEPS);
- copolymers of ethylene with at least one product chosen from salts or esters of unsaturated carboxylic acids, such as (Meth) acrylate alkyl (for example methyl acrylate), or vinyl esters of acids saturated carboxylic acids, such as vinyl acetate, the proportion of comonomer up to 40% by weight.
The functionalized polyolefin (B 1) can be an alpha polymer olefins having reactive units (functionalities); such patterns reagents are the acid, anhydride, or epoxy functions. As examples, we can cite the previous polyolefins (B2) grafted or co- or ter polymerized through unsaturated epoxides, such as glycidyl (meth) acrylate, or by acids carboxylic or the corresponding salts or esters, such as acid (meth) acrylic (which can be totally or partially neutralized by metals such as Zn, etc.), or by acid anhydrides carboxylic, such as maleic anhydride. A functionalized polyolefin East for example a PE / EPR mixture, the weight ratio of which can vary within large measures, for example between 40/60 and 90/10, this mixture being co-grafted with an anhydride, in particular maleic anhydride, according to a grafting rate for example from 0.01 to 5% by weight.
The functionalized polyolefin (B 1) can be chosen from (co) following polymers, grafted with maleic anhydride or methacrylate glycidyle, in which the grafting rate is for example from 0.01 to 5% by weight - polyethylene, polypropylene, copolymers of (ethylene with propylene, butene, hexene, or octene containing for example 35 to 80%
by weight of ethylene;
- ethylene / alpha-olefin copolymers such as ethylene / propylene, EPR (short for ethylene-propylene-rubber) and ethylene / propylene / diene (EPDM);
- styrene / ethylene-butene / styrene block copolymers (SEBS), styrene butadiene / styrene (SBS), styrene / isoprene / styrene (SIS), styrene / ethylene-propylene / styrene (SEPS);
- ethylene and vinyl acetate (EVA) copolymers, containing up to 40% by weight of vinyl acetate;
- ethylene and alkyl (meth) acrylate copolymers, containing up to 40% by weight of alkyl (meth) acrylate;
- ethylene and vinyl acetate (EVA) copolymers and (meth) alkyl acrylate, containing up to 40% by weight of comonomers.
The functionalized polyolefin (B1) can also be chosen from ethylene / propylene copolymers predominantly in propylene grafted with the maleic anhydride then condensed with polyamide (or an oligomer of polyamide) mono amine (products described in the European application No. 342.066).
The functionalized polyolefin (B 1) can also be a co- or ter-polymer of at least the following units: (1) ethylene, (2) (meth) acrylate of alkyl or vinyl ester of saturated carboxylic acid and (3) anhydride, such than maleic anhydride or (meth) acrylic acid, or epoxy, such as (meth) acrylate glycidyl. As examples of functionalized polyolefin thereof type, mention may be made of the following copolymers, where ethylene represents preferably at least 60% by weight and where the ter-monomer (the function) represents for example from 0.1 to 10% by weight of the copolymer - ethylene / alkyl (meth) acrylate / acid copolymers (meth) acrylic or maleic anhydride or glycidyl methacrylate;
- ethylene / vinyl acetate / maleic anhydride copolymers or glycidyl methacrylate;
- ethylene / vinyl acetate or (meth) acrylate copolymers / (meth) acrylic acid or maleic anhydride or glycidyl methacrylate.
In the above copolymers, (meth) acrylic acid can be salified with Zn or Li.
The term "alkyl (meth) acrylate" in polyolefins (B1) or (B2) denotes methacrylates and C1 to C8 alkyl acrylates, and may be selected among methyl facrylate, ethyl facrylate, n-butyl facrylate, acrylate iso butyl, ethyl-2-hexyl acrylate, cyclohexyl facrylate, methyl methacrylate and ethyl methacrylate.
Furthermore, the aforementioned polyolefins (B1) can also be crosslinked by any suitable process or agent (diepoxy, diacid, peroxide, etc.). The term "functionalized polyolefin" also includes blends of polyolefins mentioned above with a difunctional reagent, such as diacid, dianhydride, diepoxy, etc. likely to react with them or mixtures of at least two functionalized polyolefins capable of reacting with one another.
The copolymers mentioned above, (B 1) and (B2), can be randomly or sequentially copolymerized and have a structure linear or branched.
Molecular weight, MFI index, density of these polyolefins can also vary widely, which one skilled in the art will appreciate.
As indicated above, MFI is the abbreviation for "Melt Flow Index" and designates the melt index. It is measured according to the ASTM standard 1238.
Advantageously, the non-functionalized polyolefins (B2) are chosen from homopolymers or copolymers of polypropylene and all homopolymer of ethylene or copolymer of ethylene and a comonomer 1 S of higher alpha olefin type such as butene, hexene, octene or the 4-methyl 1-pentene. Mention may be made, for example, of polypropylene, high density polyethylenes, medium density polyethylenes, linear low density polyethylenes, low density polyethylenes and the very low density polyethylenes. These polyethylenes are known to man art as being produced according to a "radical" process, according to a catalysis of the "Ziegler" type or, more recently, according to a so-called "metallocene" catalysis.
Advantageously, the functionalized polyolefins (B1) are chosen from any polymer comprising alpha olefinic units and units carriers of polar reactive functions such as epoxy, acid carboxylic or carboxylic acid anhydride. As examples of such polymers, there may be mentioned the ter polymers of ethylene, of acrylate alkyl and malefic anhydride or glycidyl methacrylate such as LOTADER ~

of the Applicant Company or of polyolefins grafted with anhydride malefic like the OREVAC ~ of the Applicant Company as well as ter-polymers of ethylene, alkyl acrylate and (meth) acrylic acid. We may also cite grafted polypropylene homopolymers or copolymers 5 with a carboxylic acid anhydride and then condensed with polyamides or polyamide mono amino oligomers.
The MFI of polyamide, the MFI of polyolefins (B 1) and (B2) can be chosen from a wide range. It is however recommended to facilitate the dispersion of the polyolefin (B) that the MFI of the polyamide is greater than That of polyolefin (B).
For small proportions of polyolefin (B), for example 10 to 1 S
parts, it is sufficient to use a non-functionalized polyolefin (B2).
The proportion of polyolefins (B2) and (B 1) in phase (B) depends on the amount of functions present in the polyolefin (B1) as well as their reactivity.
Advantageously, weight ratios (B 1) / (B2) ranging from 5/3 are used 5 to 15/25. It is also possible, for small proportions of polyolefin (B), only use than a mixture of polyolefins (B 1) to obtain crosslinking.
According to a first preferred form of the mixture of polyamide and polyolefin, the polyolefin (B) comprises (i) a high density polyethylene 20 (HDPE) and (ü) a mixture of a polyethylene (C 1) and a polymer (C2) selected among elastomers, very low density polyethylenes and ethylene copolymers, the mixture of polymers (C1) + (C2) being co-grafted with an unsaturated carboxylic acid.
According to a variant of this first form of the mixture of polyamide and 25 of polyolefin, the polyolefin (B) comprises (i) a high polyethylene density (HDPE), (ü) a polymer (C2) chosen from elastomers, polyethylenes very low density and ethylene copolymers, the polymer (C2) being grafted with an unsaturated carboxylic acid and (iii) a chosen polymer (C'2) among elastomers, very low density polyethylenes and copolymers of ethylene.
According to a second preferred form of the mixture of polyamide and polyolefin, the polyolefin ne (B) comprises (i) polypropylene and (ü) a polyolefin which results from the reaction of a polyamide (C4) with a copolymer (C3) comprising propylene and an unsaturated monomer X, grafted or copolymerized.
According to a third preferred form of the mixture of polyamide and polyolefin, the polyolefin (B) comprises (i) a polyethylene of the LLDPE type, VLDPE or metallocene and (ü) an ethylene - (meth) acrylate copolymer - malefic anhydride.
According to a fourth preferred form of the mixture of polyamide and polyolefin, the polyamide is chosen from mixtures of (i) polyamide and (Ü) PA-6 block copolymer and PTMG blocks and mixtures of (i) polyamide and (ü) PA-12 block and PTMG block copolymer, the ratio of the quantities of copolymer and polyamide by weight being between 10/90 and 60/40. according to a first variant, the polyolefin (B) comprises (i) a polyethylene of the type LLDPE, VLDPE or metallocene and (ü) an ethylene copolymer -(meth) alkyl acrylate - maleic anhydride. According to a second variant, the polyolefin comprises two functionalized polymers comprising at least 50% by moles of ethylene units and capable of reacting to form a phase crosslinked.
As regards the first preferred form of the mixture of polyamide and polyolefin, the proportions are advantageously as follows (by weight) - 60 to 70% of polyamide, - 5 to 15% of the mixture of cografted polymers (C 1) and (C2), - the complement being a high density polyethylene.
As regards high density polyethylene, its density is advantageously between 0.940 and 0.965 and the MFI between 0.1 and 5 g / 10 min. ( 190 ° C 2.16 kg).
The polyethylene (C1) can be chosen from the polyethylenes mentioned more high. Advantageously, the polyethylene (C1) is a high density polyethylene (HDPE) with a density between 0.940 and 0.965. The MFI of (C 1) is (under 2.16 kg - 190 ° C) between 0.1 and 3 g / 10 min.
The copolymer (C2) may, for example, be an ethylene elastomer /
propylene (EPR) or ethylene / propylene / diene (EPDM). The copolymer (C2) can also be a very low density polyethylene (VLDPE) which is either a homopolymer of ethylene, a copolymer of ethylene and an alpha olefin. The copolymer (C2) can also be a copolymer of ethylene with at least one product chosen from (i) unsaturated carboxylic acids, their salts, their esters, (ü) vinyl esters of saturated carboxylic acids (iii) the unsaturated dicarboxylic acids, their salts, their esters, their hemiesters, their anhydrides. Advantageously, the copolymer (C2) is an EPR.
Advantageously, 60 to 95 parts of polyethylene (C1) are used for 40 to 5 parts of copolymer (C2).
The mixture of polymers (C 1) and (C2) is grafted with an acid unsaturated carboxylic, that is to say the polymers (C1) and (C2) are co-grafted.
We would not depart from the scope of the invention by using a functional derivative of this acid. Examples of unsaturated carboxylic acid are those having 2 to 20 carbon atoms, such as acrylic, methacrylic, malefic, fumaric and itaconic. Functional derivatives of these acids include for example anhydrides, ester derivatives, amide derivatives, derivatives imides and metal salts (such as alkali metal salts) of acids unsaturated carboxylic acids.
Unsaturated dicarboxylic acids having 4 to 10 carbon atoms and their functional derivatives, particularly their anhydrides, are particularly preferred grafting monomers.
Advantageously, maleic anhydride is used.
Various known methods can be used to graft a monomer grafting on the mixture of polymers (C 1) and (C2). For example, this can be produced by heating the polymers (C 1) and (C2) at high temperature, about 150 ° to about 300 ° C, in the presence or absence of a solvent with or without radical generator.
In the mixture of polymers (C1) and (C2) modified by grafting obtained as mentioned above, the amount of the grafting monomer can be chosen in an appropriate manner but it is preferably from 0.01 to 10%, better from 600 ppm to 2% relative to the weight of the polymers (C 1) and (C2) grafted. The amount of the grafted monomer is determined by assaying the succinic functions by IRTF spectroscopy. The MFI of polymers (C 1) and (C2) co-grafted is 5 to 30 g / 10 min. (190 ° C - 2.16 kg), from preferably 13 to 20.
Advantageously, the mixture of polymers (C 1) and (C2) co-grafted is such that the ratio MFIIO / MFI2 is greater than 18.5, MFho denoting the index flow at 190 ° C under a load of 10 kg and MFI2 the index under a load of 2.16 kg. Advantageously, the MFI2o of the mixture of polymers (C 1) and (C2) co-grafted is less than 24. MFIZO denotes the flow index at 190 ° C under a load of 21.6 kg.

As regards the variant of the first form, the proportions are advantageously the following - 60 to 70% by weight of polyamide, - 5 to 10% by weight of graft copolymer (C2), - 5 to 10% by weight of copolymer (C'2), - the remainder being a high density polyethylene.
The copolymer (C2) is advantageously an EPR or an EPDM. The copolymer (C'2) is advantageously an EPR containing by weight 70 to 75%
ethylene.
As regards the second preferred form of the mixture of polyamide and polyolefin, the proportions are advantageously as follows - 60 to 70% by weight of polyamide, - 20 to 30% by weight of polypropylene, and - 3 to 10% by weight of a polyolefin which results from the reaction of a polyamide (C4) with a copolymer (C3) comprising propylene and a unsaturated monomer X, grafted or copolymerized.
The polypropylene MFI is advantageously less than 0.5 g / 10 min (230 ° C - 2.16 kg), and preferably between 0.1 and 0.5. Such products are described in European Patent No. 647,681.
We will now describe the grafted product of this second form. We begins by preparing the copolymer (C3) which is either a copolymer of propylene and an unsaturated monomer X, i.e. a polypropylene on which graft an unsaturated monomer X. The monomer X is any unsaturated monomer can be copolymerized with propylene or grafted onto polypropylene and having a function capable of reacting with a polyamide. This function can be for example a carboxylic acid, a dicarboxylic acid anhydride or an epoxy. As examples of monomer X, mention may be made of the acid (meth) acrylic, (maleic anhydride and unsaturated epoxides, such as 5 (glycidyl meth) acrylate. Anhydride is advantageously used Maleficent.
As regards the grafted polypropylenes, the monomer X can be grafted onto homo polypropylenes or copolymers, such as ethylene copolymers propylene predominantly as propylene (in moles). Advantageously, the copolymer (C3) is such that the monomer X is grafted. Grafting is a 10 operation known per se.
Polyamide (C4) is a polyamide or a polyamide oligomer. of the polyamide oligomers are described in European patents No. 342,066 and French No. 2.291.225. Polyamides (or oligomers) (C4) are the products of condensation of the monomers already mentioned above. We can use 15 polyamide blends. PA-6, PA-11, PA- are advantageously used 12, the copolyamide with patterns 6 and patterns 12 (PA-6/12), and the copolyamide based of caprolactam, hexamethylenediamine and adipic acid (PA-6 / 6,6). The polyamides or oligomers (C4) can have acid, amine or monoamine. For the polyamide to have a monoamine ending, it suffices 20 to use a chain limiter of formula Rai H

in which RI is a hydrogen atom or a linear alkyl group or branched containing up to 20 carbon atoms, and R2 is a group having up to 20 linear or branched alkyl or alkenyl carbon atoms, one radical Saturated or unsaturated cycloaliphatic, an aromatic radical or a combination of the precedents. The limiter can for example be laurylamine or oleylamine.

Advantageously, the polyamide (C4) is a PA-6, a PA-11 or a PA-12. The proportion of polyamide (C4) in the mixture (C3) + (C4) by weight is advantageously between 0.1 and 60%. The reaction of the copolymer (C3) with the polyamide (C4) is preferably carried out in the molten state. We can by example kneading the copolymer (C3) and the polyamide (C4) in an extruder at a temperature generally between 230 and 250 ° C. Time to average stay of the melt in the extruder can be between 10 seconds and 3 minutes, and preferably between 1 and 2 minutes.
As regards the third preferred form of the mixture of polyamide and polyolefin, the proportions are advantageously as follows - 60 to 70% by weight of polyamide, and - S at 15% by weight of an ethylene copolymer - (meth) acrylate-maleic anhydride, - the complement being a polyethylene of the LLDPE, VLDPE or metallocene; advantageously, the density of this polyethylene is between 0.870 and 0.925, and the MFI is between 0.1 and 5 (190 ° C - 2.16 kg).
Advantageously, the ethylene - (meth) acrylate copolymers -maleic anhydride comprise from 0.2 to 10% by weight of maleic anhydride, up to 40%, and preferably 5 to 40% by weight of alkyl (meth) acrylate.
Their MFI is between 2 and 100 (190 ° C - 2.16 kg). The (Meth) acrylates alkyl have already been described above. The melting temperature is understood between 80 and 120 ° C. These copolymers are commercially available.
They are produced by radical polymerization at a pressure which can be understood between 200 and 2500 bars.

As regards the fourth preferred form of the mixture of polyamide and polyolefin, the proportions are advantageously as follows, depending it it is a first or a second variant.
According to the first variant:
- 60 to 70% by weight of the mixture of polyamide and of copolymer to polyamide blocks and polyether blocks, and - 5 to 15% by weight of an ethylene - (meth) acrylate copolymer - malefic anhydride, the complement being a polyethylene of the LLDPE, VLDPE or metallocene; advantageously, its density is between 0.870 and 0.925, and the MFI is between 0.1 and 5 (190 ° C - 2.16 kg).
Advantageously, the ethylene - (meth) acrylate copolymers -maleic anhydride comprise from 0.2 to 10% by weight of maleic anhydride, up to 40%, and preferably 5 to 40% by weight of alkyl (meth) acrylate.
Their MFI is between 2 and 100 (190 ° C - 2.16 kg). The (Meth) acrylates alkyl have already been described above. The melting temperature is understood between 80 and 120 ° C. These copolymers are commercially available.
They are produced by radical polymerization at a pressure which can be understood between 200 and 2500 bars.
According to the second variant:
40 to 95% by weight of the mixture of polyamide and of copolymer to polyamide blocks and polyether blocks, and - 60 to 5% by weight of a mixture of an ethylene copolymer -alkyl (meth) acrylate - maleic anhydride and an ethylene copolymer -(meth) alkyl acrylate - glycidyl methacrylate.

The anhydride copolymer was defined in the first variant. The ethylene / (meth) alkyl acrylate / glycidyl methacrylate copolymer can contain up to 40% by weight of alkyl (meth) acrylate, advantageously at 40% and up to 10% by weight of unsaturated epoxide, preferably 0.1 to 8%.
Advantageously, the alkyl (meth) acrylate is chosen from (methyl meth) acrylate, ethyl acrylate, n-butyl acrylate, acrylate isobutyl, 2-ethylhexyl acrylate. The amount of (meth) acrylate alkyl is preferably 20 to 35%. The MFI is advantageously between 5 and 100 (in g / 10 min at 190 ° C under 2.16 kg), and the melting temperature is between 60 and 110 ° C. This copolymer can be obtained by polymerization radical of the monomers.
Catalysts can be added to speed up the reaction between the epoxy and anhydride functions. Among the compounds capable of accelerating 1â
reaction between the epoxy function and the anhydride function, there may be mentioned especially:
- tertiary amines such as dimethyllaurylamine, dimethylstearylamine, N-butylmorpholine, N, N-dimethylcyclohexylamine, benzyldimethylamine, pyridine, dimethylamino-4-pyridine, methyl-1-imidazole, tetramethylethylhydrazine, N, N-dimethylpiperazine, N, N, N ', N'-tetramethyl-1,6-hexanediamine, a mixture of tertiary amines having from 16 to 18 carbons and known under the name of dimethylsuifamine, - tertiary phosphines such as triphenylphosphine, - zinc alkyldithiocarbamates, - acids.

These blends of polyamide and polyolefin can be manufactured by mixture of the constituents in the molten state according to the usual techniques of thermoplastic materials.
Regarding the inner layer of PA-11 or PA-12 in contact with (essence, polyamide can, like that of the outer layer, be laminated by common plasticizers such as n-butyl benzene sulfonamide (BBSA) and copolymers comprising polyamide blocks and polyether blocks.
The polyamide contains an electroconductive in sufficient quantity to the surface resistivity is less than 106 S2. We can cite as examples of electroconductive, metals, metal oxides and carbon products. Ä as examples of carbon-based products, we may include graphite, carbon black aggregates, carbon, the carbon nanotubes and activated carbon. We would not go outside the framework of the invention using several elements.
For carbon black, the proportion is usually understood between 5 and 30 parts by weight of black per 100 parts of the whole polyamide and its plasticizers and other additives.
These multilayer tubes can be cylindrical with a constant diameter or ringed.
Conventionally, these tubes may include sheaths of protection including rubber to protect them from hot spots engine.

Claims (20)

1. Multilayer tube comprising successively in one direction radial from outside to inside:
- a first layer formed from a polyamide chosen from the group consisting of poly (undecanoamide) and polylauryllactam, the first layer defining an outer layer;
- a second layer formed of a binder;
- a third layer formed of an ethylene-alcohol copolymer vinyl;
a fourth layer formed from a mixture of polyamide and polyolefin with polyamide matrix;
- a fifth layer formed of a binder; and - a sixth layer formed from a polyamide chosen from the group consisting of poly (undecanoamide) and polylauryllactam, and comprising a dispersed charge of an electroconductor producing a resistivity surface area less than 10 6 .OMEGA., the sixth layer defining a layer indoor;
the first, second, third, fourth, fifth and sixth layers each having a contact zone and adhering to each other in their zone of respective contact. 2. Tube according to claim 1, characterized in that the sixth inner layer contains enough carbon black for the surface resistivity is less than 10 6 .OMEGA .. 3. Tube according to claim 1 or 2, characterized in that the first layer is formed of poly (undecanoamide) and the binder between said first layer and the third layer is based on polyolefins functionalized. 4. Tube according to claim 1 or 2, characterized in that the first layer is formed of polylauryllactam and the binder between said first layer and the third layer is based on copolyamides. 5. Tube according to any one of claims 1 to 4, characterized in that the sixth layer is formed of poly (undecanoamide) and the binder Between the fourth layer and said sixth layer is based on polyolefins functionalized. 6. Tube according to any one of claims 1 to 5, characterized in that the sixth layer is formed of polylauryllactam and the binder between the fourth layer and said sixth layer is based on copolyamides. 7. Tube according to claim 4 or 6, characterized in that the copolyamides result from the condensation of at least two alpha omega acids aminocarboxylic or at least two lactams having from 6 to 12 atoms of carbon or a lactam and an aminocarboxylic acid not having the same number of carbon atoms. 8. Tube according to claim 4 or 6, characterized in that the copolyamides result from the condensation of at least one alpha-omega acid aminocarboxylic, at least one diamine and at least one dicarboxylic acid. 9. Tube according to claim 4 or 6, characterized in that the copolyamides result from the condensation of at least one lactam, at least one diamine and at least one dicarboxylic acid. 10. Tube according to claim 4 or 6, characterized in that the copolyamides comprise a mixture of two copolyamides resulting from the condensation of caprolactam with lauryllactam, one of which is rich in motifs derived from caprolactam and the other is rich in motifs derived from lauryllactam. 11. Tube according to claim 10, characterized in that the copolyamide rich in units derived from caprolactam comprises 60 to 90% by weight of units derived from caprolactam for respectively 40 to 10% by weight of motifs derived from lauryllactam. 12. Tube according to claim 10 or 11, characterized in that the copolyamide rich in units derived from lauryllactam comprises 60 to 90% in weight of units derived from lauryllactam for respectively 40 to 10% by weight of units derived from caprolactam. 13. Tube according to any one of claims 10 to 12, characterized in that the polyamide blend comprises rich copolyamide in units derived from caprolactam and copolyamide rich in units derived from lauryllactame in a ratio of 40/60 to 60/40. 14. Tube according to any one of claims 1 to 13, characterized in that the polyolefin of the mixture of polyamide and matrix polyolefin polyamide comprises (i) a high density polyethylene and (ii) a mixture of a polyethylene C1 and a polymer C2 chosen from the group consisting of elastomers, very low density polyethylenes and copolymers of ethylene, the mixture of polyethylene C1 and polymer C2 being co-grafted with an unsaturated carboxylic acid. 15. Tube according to any one of claims 1 to 13, characterized in that the polyolefin of the mixture of polyamide and matrix polyolefin polyamide comprises (i) a high density polyethylene, (ii) a polymer C2 chosen from the group consisting of elastomers, polyethylenes of very low density and ethylene copolymers, polymer C2 being grafted through an unsaturated carboxylic acid, and (iii) a polymer C'2 chosen from the group made up of elastomers, very low density polyethylenes and ethylene copolymers. 16. Tube according to any one of claims 1 to 13, characterized in that the polyolefin of the mixture of polyamide and matrix polyolefin polyamide comprises (i) polypropylene and (ii) a polyolefin resulting from the reaction of a polyamide with a copolymer comprising propylene and a unsaturated, grafted or copolymerized monomer. 17. Tube according to any one of claims 1 to 13, characterized in that the polyolefin of the mixture of polyamide and matrix polyolefin polyamide comprises (i) a polyethylene of the LLDPE, VLDPE or metallocene and (ii) an ethylene - (meth) acrylate copolymer -anhydride Maleficent. 18. Tube according to any one of claims 1 to 13, characterized in that the polyamide of the blend of polyamide and polyolefin with matrix polyamide is chosen from the group consisting of mixtures of (i) polyamide and (ii) polycapronamide block copolymer and polytetra methylene glycol blocks and mixtures of (i) polyamide and (ii) polylauryllactam block copolymer and polytetra methylene glycol blocks; the ratio of the amounts of copolymer and polyamide by weight being between 10/90 and 60/40. 19. Tube according to claim 18, characterized in that the polyolefin of the mixture of polyamide and polyolefin with polyamide matrix includes (i) a polyethylene of the LLDPE, VLDPE or metallocene type and (ii) a ethylene - alkyl (meth) acrylate - maleic anhydride copolymer. 20. Structure according to claim 18, characterized in that the polyolefin of the mixture of polyamide and polyolefin with polyamide matrix includes two functionalized polymers comprising at hand 50% by moles of ethylene units and capable of reacting to form a crosslinked phase.