FR2876768A1 - Multi-layer tube, useful for transporting cooling liquid, comprises: external polyamide layer; and interior composition layer - Google Patents

Abstract

Multi-layer tube (I) comprises (having radial direction from exterior towards interior): an external polyamide layer (II); and an interior layer (III) of a composition (containing mixture (A) (5-30 wt.%) (comprising a polyethylene with epoxy group and an impact modifier (elastomers and polyethylene)) and mixture (B) (95-70 wt.%) comprising a fluorinated polymer and a functionalized fluorinated polymer). Multi-layer tube (I) comprises (having radial direction from exterior towards interior): an external polyamide layer; and an interior layer of a composition (containing mixture (A) (5-30 wt.%) (comprising a polyethylene with epoxy group and an modifying impact (elastomers and polyethylene) of very low density, where the modifier is functionalized in whole or part) and mixture (B) (95-70 wt.%) comprising a fluorinated polymer and a functionalized fluorinated polymer), where the ratio fluorinated polymer is 1-60 wt.% and the layer is successive and adhere to one another in their respective zone of contact.

Description

Field of the invention

  The present invention relates to a multilayer pipe based on polyamide and fluoropolymer for transferring fluids.

  By way of example of tubes for the transfer of fluid, mention may be made of tubes for gasoline, and in particular for bringing gasoline from the tank to the engine of automobiles. By way of other examples of fluid transfer, mention may be made of the fluids used in the fuel cell, the CO2 system for cooling and air conditioning, the hydraulic systems and the cooling circuit. air conditioning and power transfers at medium pressure.

  For reasons of safety and preservation of the environment, car manufacturers impose on these tubes both mechanical characteristics such as bursting resistance and flexibility with good resistance to cold shocks (-40 C). as well as at high temperature (125 ° C.), and also a very low permeability to hydrocarbons and their additives, in particular alcohols such as methanol and ethanol. These tubes must also have good resistance to fuels and engine lubricating oils. These tubes are manufactured by coextrusion of the different layers according to the usual techniques of thermoplastics.

  One particular use relates to tubes for the cooling circuits of internal combustion engines such as engines of automobiles or trucks. Coolants are generally aqueous solutions of alcohols such as, for example, ethylene glycol, diethylene glycol or propylene glycol. These tubes must also have good mechanical strength and withstand the engine environment (temperature, presence of oil). They can be smooth (of constant diameter) or be corrugated or have annular parts and smooth parts.

  PRIOR ART AND THE TECHNICAL PROBLEM US Pat. No. 5,560,398 describes tubes for a cooling circuit consisting of an outer layer of polyamide and an inner layer chosen from polyolefins, fluoropolymers, polyesters and EVAs (copolymers of ethylene and vinyl acetate).

  US Pat. No. 5,716,684 discloses cooling circuit tubes consisting of an outer layer of polyamide, a binder consisting of a mixture of polyvinylidene fluoride and polyamide and an inner layer of polyvinylidene fluoride.

  No. 5,706,664 discloses cooling circuit tubes consisting of an outer layer of polyamide and an inner layer of either PVDF or polyolefin or polyolefin grafted with carboxylic acid anhydride. A binder must be placed between these two layers in the case where the outer layer is a polyamide and the inner layer a PVDF.

  US Pat. No. 5,850,855 describes tubes for a cooling circuit consisting in this order of an outer layer of amine-terminated polyamide, a layer of polyethylene grafted with maleic anhydride and an inner layer of polyolefin or HDPE ( abbreviation of High Density Polyethylene or high density polyethylene) grafted with silanes. According to one variant, they consist in this order of an outer layer of amine-terminated polyamide, of a polypropylene layer grafted with maleic anhydride and of an inner layer which is a mixture of polypropylene and elastomer EPDM ( ethylene-propylene-diene elastomer).

  EP 1 104 526 discloses a tube having in its radial direction, from the inside to the outside, a so-called inner layer, based on a fluorinated resin (or polymer) and intended to come into contact with a circulating fluid. characterized in that the inner layer is formed of a mixture comprising a semicrystalline thermoplastic fluorinated resin (eg PVDF) and a triblock copolymer ABC, the three blocks A, B, and C being connected together in that order, each block being either a homopolymer or a copolymer obtained from two or more monomers, block A being connected to block B and block B to block C by means of a covalent bond or an intermediate molecule connected to one of these blocks by a covalent bond and to the other block by another concovalent bond, and in that: the block A is compatible with the fluororesin, the block B is incompatible with the fluororesin and is incompatible with the block A, - the Block C is incompatible with the fluororesin, block A and block B, the outer layer of the tube being made of polyamide.

  This PVDF-based layer resists shock while remaining a barrier to gasoline. However, it remains to ensure adhesion to the polyamide layer.

  In all the above structures the use of a binder is necessary when a layer of PA and PVDF are coextruded. These binders have a low resistance to transported fluids, leading to premature aging of the multilayer structure. On the other hand, the use of PVDF in the inner layer poses the problem of the resistance of the structure to cold shock. The use of conventional impact modifiers PVDF significantly improves the cold shock but significantly reduces its chemical resistance and increases its permeability to the fluids transported.

  The prior art has already described tubes comprising an outer polyamide layer and at least one other PVDF layer. In these tubes of the prior art complex compositions are described to ensure the adhesion of polyamide and PVDF. In addition, these tubes do not concern the coolant.

  EP 558373 discloses a tube for transporting gasoline respectively comprising a polyamide outer layer, a binder layer and an inner layer in contact with the gasoline and consisting of fluoropolymer.

  Patents EP 696301, EP 740754 and EP 726926 disclose tubes for transporting gasoline respectively comprising a polyamide outer layer, a binder layer, a PVDF (polyvinylidene fluoride) layer, a binder layer and an inner layer. polyamide in contact with gasoline.

  Other polyamide and PVDF-based gasoline transport tubes are described in US 5,472,784, US 5,474,822, US 5,500,263, US 5,510,160, US 5,512,342 and US 5,554,426. .

  We have now found a functional fluoropolymer-based mixture capable of direct adhesion to polyamides making it possible to prepare multilayer structures which are particularly well suited to transporting fluids. The composition has excellent resistance to solvents, alcoholic essences, coolants and very low permeability. The invention also relates to the impact modification, made possible by the functionalization of the fluoropolymer, by impact modifiers that are insensitive to the fluids transported.

Brief description of the invention

  The present invention relates to a multilayer tube comprising in its radial direction from the outside to the inside: an outer layer (1) of polyamide, an inner layer (2) of a composition comprising, the total being 100%: 5 to 30% by weight of a mixture (A) comprising: a polyethylene bearing epoxy functional groups, an impact modifier selected from elastomers and very low density polyethylenes, said impact modifier being wholly or partly functionalized, at 70% by weight; weight of a mixture (B) comprising: a fluorinated polymer (B1), a functionalized fluoropolymer (B2), the proportion of (B1) is between 1 and 60% by weight of (A) + (B), the layers being successive and adhering to each other in their respective contact zone. The inner layer is the layer in contact with the transported fluid.

  According to another form the invention relates to a multilayer tube comprising in its radial direction from the outside to the inside: an outer layer (1) of polyamide, a layer (2) of a composition comprising, the total being 100% at 30% by weight of a mixture (A) comprising: a polyethylene bearing epoxy functions, an impact modifier selected from elastomers and very low density polyethylenes, said impact modifier being wholly or partly functionalized, 95 to 70 % by weight of a mixture (B) comprising: a fluorinated polymer (B1), a functionalized fluoropolymer (B2), the proportion of (B1) is between 1 and 60% by weight of (A) + (B) , an inner layer (3) of polyolefin, the layers being successive and adhering to each other in their respective contact zone. The inner layer is the layer in contact with the transported fluid.

  According to an advantageous form there is disposed between the layer (2) and the layer (3) a functionalized polyolefin layer having functions capable of reacting with the functions of the fluorinated polymer (B2).

  According to one advantageous form, the polyamide of the outer layer (1) is an amine-terminated polyamide or comprising more amine terminations than acid terminations.

  According to an advantageous form there is disposed between the outer layer (1) and the layer (2) an amino-terminated polyamide layer or comprising more amine terminations than acid terminations.

  According to another form one can combine these two previous forms. These tubes may have an outside diameter of 6 to 110 mm and a thickness of the order of 0.5 to 5 mm.

  Advantageously, the tube for coolant according to the invention has an outer diameter ranging from 8 to 40 mm and a total thickness of 0.8 to 2.5 mm. The outer layer (1) represents between 30 and 80% of the thickness of the tube. In the tubes having an inner layer (3) the thickness of the outer layer (1) is between 25 and 50% of the thickness of the tube.

  The tube of the present invention is very little permeable to the cooling liquid and its additives (boric acid and its salts). These tubes also have good resistance to fuels and engine lubricating oils.

  This tube has very good mechanical properties at low or high temperature. These tubes may be smooth or corrugated.

  The invention also relates to the use of these tubes for the transport of coolant.

  Detailed description of the invention

  With regard to the polyamide of the outer layer (1), mention may be made of PA 11 and PA 12.

  Mention may also be made of those of formula XY / Z or 6.Y2 / Z in which: X denotes the residues of an aliphatic diamine having from 6 to 10 carbon atoms, Y denotes the residues of an aliphatic dicarboxylic acid having from 10 to 10 carbon atoms; at 14 carbon atoms, Y 2 denotes the residues of an aliphatic dicarboxylic acid having from 15 to 15 carbon atoms, Z denotes at least one unit chosen from the residues of a lactam, the residues of an alpha-omega amino acid carboxylic acid, the unit X1.Y1 in which X1 denotes the residues of an aliphatic diamine and Y1 denotes the remains of an aliphatic dicarboxylic acid, the weight ratios Z / (X + Y + Z) and Z / (6 + Y2) + Z) being between 0 and 15%.

  By way of example, mention may be made of PA 6.10 (hexamethylene diamine and sebacic acid units), PA 6.12 (hexamethylene diamine and dodecanedioic acid units) and PA 10.10 (1,10-decanediamine and sebacic acid units).

  Mention may also be made of polyamides of formula X / Y, Ar in which: Y Y denotes the residues of an aliphatic diamine having from 8 to 20 carbon atoms, wherein Ar denotes the residues of an aromatic dicarboxylic acid, and X denotes either the residues of the aminoundecanoic acid NH 2 - (CH 2) 10 -COOH, the lactam 12 or the corresponding amino acid is the unit Y, x remains of the condensation of the diamine with an aliphatic diacid (x) having between 8 and 20 atoms of carbon is still the unit Y, the rest of the condensation of the diamine with isophthalic acid, X / Y, Ar designates for example: - the 11/10, which results from the condensation of the aminoundecanoic acid , 1,12-decanediamine and terephthalic acid, - 12/12, which results from the condensation of lactam 12, 1,12-dodecanediamine and terephthalic acid, - 10,10 / 10, T which results from the condensation of sebacic acid, 1,10-decanediamine and terephthalic acid, the 10, 1/10, T which results condensation of isophthalic acid, 1,10-decanediamine and terephthalic acid.

  The inherent viscosity of the polyamide of the outer layer (1) can be between 1 and 2 and preferably between 1.2 and 1.8. The inherent viscosity is measured at 20 ° C for a concentration of 0.5% in metacresol. The polyamide of the outer layer (1) may contain from 0 to 30% by weight of at least one product chosen from plasticizers and impact modifiers for 100 to 70% of polyamide, respectively. This polyamide may contain the usual anti-UV additives, stabilizers, antioxidants, flame retardants, etc. With regard to the mixture (A) and first of the polyethylene carrying epoxy functions it may be a polyethylene on which epoxy functional groups or a copolymer of ethylene and an unsaturated epoxide have been grafted. .

  Examples of copolymers of ethylene and an unsaturated epoxide include ethylene copolymers of an alkyl (meth) acrylate and an unsaturated epoxide or copolymers of ethylene, a saturated carboxylic acid vinyl ester and an unsaturated epoxide. The amount of epoxide can be up to 15% by weight of the copolymer and the amount of ethylene of at least 50% by weight. Advantageously, the proportion of epoxide is between 2 and 12% by weight. Advantageously, the proportion of alkyl (meth) acrylate is between 0 and 40% by weight and preferably between 5 and 35% by weight.

  Advantageously, it is a copolymer of ethylene of an alkyl (meth) acrylate and an unsaturated epoxide.

  Preferably the alkyl (meth) acrylate is such that the alkyl has 1 to 10 carbon atoms.

  The MFI (melt flow index) can be for example between 0.1 and 50 (g / 10 min at 190 ° C. under 2.16 kg).

  Examples of alkyl acrylate or methacrylate which can be used are in particular methyl methacrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, acrylate and the like. 2-ethylhexyl. Examples of unsaturated epoxides that may be used include: aliphatic glycidyl esters and ethers such as glycidyl allyl glycidyl ether, vinyl glycidyl ether, maleate and itaconate, glycidyl acrylate and methacrylate, and esters and alicyclic glycidyl ethers such as 2-cyclohexene-glycidyl ether, cyclohexene-4,5-diglycidylcarboxylate, cyclohexene-4-glycidyl carboxylate, 5-norbornene-2-methyl-2-glycidyl carboxylate and endocisbicyclo (2,2,1) -5-heptene-2,3-diglycidyl dicarboxylate.

  As regards the mixture (A) and now the impact modifier and first elastomers include block polymers SBS, SIS, SEBS, and elastomers ethylene / propylene (EPR) or ethylene / propylene / diene (EPDM). As for the very low density polyethylenes are for example metallocenes of density for example between 0.860 and 0.900. Acrylic elastomers are not suitable because they cause permeability to gasoline. Acrylic elastomers are elastomers based on at least one monomer chosen from acrylonitrile, alkyl (meth) acrylate and core shell (core shell). As regards the bark core copolymer, it is in the form of fine particles having an elastomer core and at least one thermoplastic bark (usually made of PMMA), the particle size is generally less than the pm and advantageously between 50 and 300 nm.

  Advantageously, an ethylene / propylene (EPR) or ethylene / propylene / diene (EPDM) elastomer is used. The functionalization may be provided by grafting or copolymerization with an unsaturated carboxylic acid. It would not depart from the scope of the invention using a functional derivative of this acid. Examples of unsaturated carboxylic acid are those having 2 to 20 carbon atoms such as acrylic, methacrylic, maleic, fumaric and itaconic acids. Functional derivatives of these acids include, for example, anhydrides, ester derivatives, amide derivatives, imide derivatives and metal salts (such as alkali metal salts) of unsaturated carboxylic acids.

  Unsaturated dicarboxylic acids having 4 to 10 carbon atoms and their functional derivatives, particularly their anhydrides, are particularly preferred grafting monomers. These grafting monomers comprise, for example, maleic, fumaric, itaconic, citraconic, allylsuccinic, cyclohex-4-ene-1,2-dicarboxylic, 4-methylcyclohex-4-ene-1,2-dicarboxylic, and bicyclo (2.2 , I) -hept-5-ene-2,3dicarboxylic acid, x-methylbicyclo (2,2,1) -hept-5-ene-2,3-dicarboxylic acid, maleic, itaconic, citraconic, allylsuccinic, cyclohexene-4-ene anhydrides 1,2-dicarboxylic, 4-methylenecyclohex-4-ene-1,2-dicarboxylic, bicyclo (2,2,1) hept-5-ene-2,3-dicarboxylic acid, and x-methylbicyclo (2,2, 1) hept-5-ene-2,2-dicarboxylic acid. Maleic anhydride is advantageously used.

  Various known methods can be used to graft a grafting monomer onto a polymer. For example, this can be done by heating the polymers at elevated temperature, about 150 to about 300 ° C, in the presence or absence of a solvent with or without a radical generator. The amount of the grafting monomer may be suitably selected but is preferably from 0.01 to 10%, more preferably from 600 to 2% based on the weight of the polymer to which the graft is attached.

  As regards the functionalized fluoropolymer (B2) and firstly the fluoropolymer is denoted as any polymer having in its chain at least one monomer chosen from compounds containing a vinyl group capable of opening to polymerize and which contains, directly attached to this vinyl group, at least one fluorine atom, a fluoroalkyl group or a fluoroalkoxy group.

  By way of example of monomer, mention may be made of vinyl fluoride; vinylidene fluoride (VDF); trifluoroethylene (VF3); chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro (alkyl vinyl) ethers such as perfluoro (methyl vinyl) ether (PMVE), perfluoro (ethyl vinyl) ether (PEVE) and perfluoro (propyl vinyl) ether (PPVE); The fluoropolymer may be a homopolymer or a copolymer, it may also include non-fluorinated monomers such as ethylene.

  By way of example, the fluorinated polymer is chosen from: homo-and copolymers of vinylidene fluoride (VDF) preferably containing at least 50% by weight of VDF, the copolymer being chosen from chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), trifluoroethylene (VF3) and tetrafluoroethylene (TFE), homo-and copolymers of trifluoroethylene (VF3), copolymers, and especially terpolymers, combining the residues of the chlorotrifluoroethylene (CTFE), tetrafluoroethylene (TFE) units , hexafluoropropylene (HFP) and / or ethylene and optionally VDF and / or VF3 units.

  - Copolymers of ethylene and tetrafluoroethylene (ETFE) can also be mentioned.

  Advantageously, the fluoropolymer is polyvinylidene fluoride (PVDF) homopolymer or copolymer. Preferably the PVDF contains, by weight, at least 50% of VDF, more preferably at least 75% and more preferably at least 85%. The comonomer is advantageously HFP. Advantageously, the PVDF has a viscosity ranging from 100 Pa.s to 2000 Pa.s, the viscosity being measured at 230 ° C., at a shear rate of 100 s "'using a capillary rheometer. these PVDFs are well suited to extrusion and injection, preferably PVDF has a viscosity ranging from 300 to 2876768 Pa.s at 1200 Pa.s, the viscosity being measured at 230 C. at a shear rate 100s'1 using a capillary rheometer.

  By way of example of functionalized fluoropolymer, mention may be made of that grafted with an unsaturated monomer. it can be manufactured according to a grafting process in which: a) the molten fluoropolymer is mixed with the unsaturated monomer, b) the mixture obtained in a) is formed into films, plates, granules. c) the products of step b) are subjected, in the absence of air, to photonic (y) or electronic (R) irradiation at a dose of between 1 and 15 Mrad, d) the product obtained in c) is optionally treated to remove all or part of the unsaturated monomer which has not been grafted onto the fluoropolymer.

  As regards the unsaturated grafting monomer, examples that may be mentioned include carboxylic acids and their derivatives, acid chlorides, isocyanates, oxazolines, epoxides, amines or hydroxides. Examples of unsaturated carboxylic acids are those having 2 to 20 carbon atoms such as acrylic, methacrylic, maleic, fumaric and itaconic acids. Functional derivatives of these acids include, for example, anhydrides, ester derivatives, amide derivatives, imide derivatives and metal salts (such as alkali metal salts) of unsaturated carboxylic acids. Mention may also be made of undecylenic acid and zinc undecylenate.

  Unsaturated dicarboxylic acids having 4 to 10 carbon atoms and their functional derivatives, particularly their anhydrides, are particularly preferred grafting monomers.

  Step a) is carried out in any mixing device such as extruders or kneaders used in the thermoplastics industry.

  With regard to the proportions of the fluoropolymer and the unsaturated monomer, the proportion of fluorinated polymer is advantageously, by weight, from 90 to 99.9% for 0.1 to 10% of unsaturated monomer, respectively. Preferably, the proportion of fluoropolymer is from 95 to 99.9% for 0.1 to 5% of unsaturated monomer, respectively.

  At the end of step a), it is found that the mixture of the fluoropolymer and the unsaturated monomer lost about 10 to 50% of the unsaturated monomer introduced at the beginning of step a). This proportion depends on the volatility and the nature of the unsaturated monomer. In fact, the monomer has been degassed in the extruder or mixer and is recovered in the vent circuits.

  With regard to step c), the products recovered after step b) are advantageously packaged in polyethylene bags and the air is removed and they are closed. During this grafting step, it is preferable to avoid the presence of oxygen. A nitrogen or argon sweep of the fluoropolymer / graftable compound mixture is therefore possible to remove oxygen.

  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. This results in a grafting of the unsaturated monomer by 0.1 to 5% by weight (that is to say that the unsaturated grafted monomer corresponds to 0.1 to 5 parts for 99.9 to 95 parts of fluoropolymer ), preferably from 0.5 to 5%, preferably from 0.5 to 1.5%; more preferably 0.7 to 1.5%; more preferably 0.8 to 1.5%; more preferably from 0.9 to 1.5% more preferably from 1 to 1.5%. 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.

  As regards step d), the non-grafted monomer and the residues released by the grafting, in particular HF, can be removed by any means. The proportion of grafted monomer relative to the monomer present at the beginning of step c) is between 50 and 100%. It can be washed with inert solvents with respect to the fluoropolymer and grafted functions. For example when grafting maleic anhydride can be washed with chlorobenzene. It can also be more easily degassed by evacuating, possibly simultaneously applying a heating, the product recovered in step c). This operation can be performed according to techniques known to those skilled in the art. 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.

  By way of example of a functionalized fluoropolymer, mention may also be made of that grafted with an unsaturated monomer but by a radical route. The unsaturated monomer may be chosen from those mentioned above. This method is less effective than irradiation grafting, more than 0.8% of unsaturated monomer can not be grafted and there is a risk of degrading the fluoropolymer. However, this product may be suitable for simple conditions of use.

  This is one of the advantages of this irradiation 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%, whereas with a conventional grafting process in an extruder, the content is of the order of 0.2 to 0.8%. On the other hand, the grafting by irradiation takes place cold, typically at temperatures below 100 C, or even 70 C, so that the mixture of the fluorinated polymer and the unsaturated monomer is not in the molten state as for a conventional grafting process in an extruder. An essential difference is therefore that, in the case of a semi-crystalline fluorinated polymer (as for PVDF for example), the grafting takes place in the amorphous phase and not in the crystalline phase, while homogeneous grafting occurs. in the case of an extruder grafting. The unsaturated monomer is therefore not distributed 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 graftable compound on the chains of the fluoropolymer compared to a product which would be obtained by grafting in an extruder.

  By way of example of functionalized fluoropolymer, mention may also be made of those in which a functional monomer or a functional element is incorporated during the polymerization. Such functionalized fluoropolymers are described in US Patents 5,415,958, US 6,680,124, US 6,703,465 and US Patent Application 2004-0191440.

  As regards the fluoropolymer (E31), it can be chosen from the same polymers as (B2). (BI) may be the same polymer as (B2) but not functionalized or different.

  As regards the proportions of (A) are advantageously from 5 to 10% for respectively 95 to 90% of (B). The proportion of polyethylene carrying epoxy functions may be from 1 to 2 parts per 5 parts of the impact modifier. The proportion of (BI) is advantageously between 35 and 60%, preferably between 45 and 55% by weight of (A) + (B).

  With regard to the preparation of the compositions of the invention they can be prepared by melt blending of the constituents according to the usual techniques of thermoplastic materials.

  The mixtures of (A) and (B) may additionally contain at least one additive chosen from: dyes; pigments; antioxidants; flame retardants; UV stabilizers; nanofillers; nucleating agents.

  As regards the form of the invention in which the tube comprises an inner layer (3), this layer (3) is made of polyolefin. It can be functionalized or non-functionalized or be a mixture of at least one functionalized and / or at least one non-functionalized.

  An unfunctionalized polyolefin is a homopolymer or copolymer of alpha olefins or diolefins, such as, for example, ethylene, propylene, butene-1, octene-1, butadiene. By way of example, mention may be made of: Homopolymers and copolymers of polyethylene, in particular LDPE, HDPE, LLDPE (linear low density polyethylene or linear low density polyethylene), VLDPE (very low density polyethylene, or very low polyethylene) density) and metallocene polyethylene.

  homopolymers or copolymers of propylene.

  ethylene / alpha-olefin copolymers such as ethylene / propylene, EPR (abbreviation of 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 unsaturated carboxylic acid salts or esters, such as alkyl (meth) acrylate (for example methyl acrylate), or vinyl esters of carboxylic acids Saturated such as vinyl acetate (EVA), the proportion of comonomer up to 40% by weight.

  The functionalized polyolefin may be a polymer of alpha olefins having reactive units (functionalities); such reactive units are acid, anhydride or epoxy functions. By way of example, non-functionalized polyolefins which have been grafted or copolymerized with unsaturated epoxides such as glycidyl (meth) acrylate, or with carboxylic acids or the corresponding salts or esters such as (meth) acrylic acid (which may be totally or partially neutralized by metals such as Zn, etc.) or by anhydrides of carboxylic acids such as maleic anhydride. A functionalized polyolefin is for example a PE / EPR mixture, the weight ratio of which can vary widely, for example between 40/60 and 90/10, said mixture being co-grafted with an anhydride, in particular maleic anhydride, according to a grafting rate of, for example, 0.01 to 5% by weight.

  The functionalized polyolefin may be chosen from the following (co) polymers, grafted with maleic anhydride or glycidyl methacrylate, in which the degree of grafting is, for example, from 0.01 to 5% by weight: PE, PP, copolymers 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 (abbreviation of 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-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) and alkyl (meth) acrylate copolymers containing up to 40% by weight of comonomers.

  The functionalized polyolefin may also be chosen from ethylene / propylene predominantly propylene copolymers grafted with maleic anhydride and then condensed with monoamino polyamide (or a polyamide oligomer) (products described in EP-A-0342066).

  The functionalized polyolefin may also be a co- or ter polymer of at least the following units: (1) ethylene, (2) alkyl (meth) acrylate or saturated carboxylic acid vinyl ester and (3) anhydride such as maleic anhydride or (meth) acrylic acid or epoxy such as glycidyl (meth) acrylate. By way of example of functionalized polyolefins of the latter type, mention may be made of the following copolymers, in which ethylene is preferably at least 60% by weight and in which the monomer ter (the function) represents, for example, from 0.1 to 10% by weight of the copolymer: ethylene / alkyl (meth) acrylate / (meth) acrylic acid or maleic anhydride or glycidyl methacrylate copolymers; ethylene / vinyl acetate / maleic anhydride or glycidyl methacrylate copolymers; In the foregoing copolymers, the (meth) acrylic acid may be salified with Zn or Li.

  The term "alkyl (meth) acrylate" refers to C1-C8 alkyl methacrylates and acrylates, and may be selected from methyl acrylate, ethyl acrylate, n-butyl acrylate, and the like. iso-butyl acrylate, ethyl-2-hexyl acrylate, cyclohexyl acrylate, methyl methacrylate and ethyl methacrylate.

  Moreover, the functionalized polyolefins mentioned above can also be crosslinked by any suitable method or agent (diepoxy, diacid, peroxide, etc.); the term "functionalized polyolefin" also includes mixtures of the aforementioned polyolefins with a difunctional reagent such as diacid, dianhydride, diepoxy, etc. capable of reacting with them or mixtures of at least two functionalized polyolefins that can react with one another.

  The copolymers mentioned above can be copolymerized randomly or sequentially and have a linear or branched structure.

  The molecular weight, the MFI index and the density of these polyolefins may also vary to a large extent, which the skilled person will appreciate. MFI, abbreviation of Melt Flow Index, is the melt flow index. It is measured according to ASTM 1238.

  Advantageously, the non-functionalized polyolefins are chosen from homopolymers or copolymers of polypropylene and any homopolymer of ethylene or copolymer of ethylene and a comonomer of higher alpha olefinic type such as butene, hexene or octene. or 4-methyl-1-pentene. We can cite, for example, PP, high density PE, medium density PE, linear low density PE, low density PE, very low density PE. These polyethylenes are known to those skilled in the art as being produced according to a radical process, according to a Ziegler-type catalysis or according to a so-called metallocene catalysis.

  Advantageously, the functionalized polyolefins are chosen from any polymer comprising alpha olefinic units and units carrying polar reactive functional groups such as the epoxy, carboxylic acid or carboxylic acid anhydride functions. By way of examples of such polymers, mention may be made of ter polymers of ethylene, alkyl acrylate and maleic anhydride or of glycidyl methacrylate, such as the Lotader's of the Applicant or polyolefins grafted with maleic anhydride such as the Orevacs of the Applicant as well as ter polymers of ethylene, alkyl acrylate and (meth) acrylic acid. Mention may also be made of homopolymers or copolymers of polypropylene grafted with a carboxylic acid anhydride and then condensed with polyamides or monoamino oligomers of polyamide. The polyolefin of the layer (3) may also contain a functionalized polyolefin having functions capable of reacting with the functions of the fluoropolymer (B2) of the adjacent layer.

  According to an advantageous form there is disposed between the layer (2) and the layer (3) a functionalized polyolefin layer having functions capable of reacting with the functions of the fluorinated polymer (B2).

  For example, if maleic anhydride has been grafted onto the fluoropolymer (B2), the functionalized polyolefin layer consists of a polyethylene carrying epoxy functional groups. Such polymers have been mentioned above. Advantageously, the functionalized polyolefin layer consists of a copolymer of ethylene, of glycidyl methacrylate and optionally of an alkyl acrylate optionally mixed with polyethylene.

Examples

  The following polymers were used: Kynar 720: PVDF homopolymer from the company ARKEMA and MVI (Melt Volume Index) 7 cc / 10 min (230 C, 5 kg).

  Kynar ADX 120: PVDF functional homopolymer grafted with maleic anhydride from the company ARKEMA and MVI (Melt Volume Index) (melt flow volume index) 7 cm3 / 10 min (230 C, 5 kg).

  Kynar 740: PVDF homopolymer of the company ARKEMA and MVI (Melt Volume Index) 1 cm3 / 10 min (230 C, 5kg).

  Kynar ADX 140: PVDF functional homopolymer grafted with maleic anhydride from the company ARKEMA and MVI (Melt Volume Index) 1 cm3 / 10 min (230 C, 5 kg).

  Paraloid EXL 3600: shock modifier MBS heart-bark type (Rhom and Haas).

  LOTADER 8840: copolymer of ethylene and glycidyl methacrylate from the company ARKEMA and MVI (Melt Volume Index) 5 cm3 / 10 min (190 C 2.16 kg). It contains 92% ethylene and 8% glycidyl methacrylate by weight.

  EXXELOR VA 1803: EPR elastomer grafted with maleic anhydride, MFI 3 g / 10 min (230 C-2.16 kg).

  Rilsan AESN P110 TL: impact modified polyamide 12 from the company ARKEMA NECHVO: polyamide 12 at the end of the chain, mainly amine of the ARKEMA company Example 1: according to the invention In a Werner 40 extruder, a mixture of Kynar 740 (44% by weight), with 50% Kynar ADX 140, 1% LOTADER 8840 and 25% EXXELOR VA 1803.

  On a McNeil line at 230 ° C., a three-layer tube having a thickness of 1. 5 mm and an outer diameter of 12 mm composed of an outer layer of AESN P110 TL (1250 μm), NECHVO (50 μm) and the preceding PVDF alloy was extruded on a McNeil line. inner layer (200pm).

  This tube tested pendulum shock according to DIN 73378 with a pendulum of 7.5J does not break at 23 C nor at -30 C.

  Aging is carried out for 300 hours at 130 ° C. in a ventilated oven, the inside of the tube being filled with a cooling liquid composed of 50% water and 50% coolant (Havoline produced by Texaco), the outside the tube being in contact with the atmosphere of the enclosure. At the end of this aging tube tested pendulum shock does not break at 23 C or -30 C.

  The permeability of this bilayer tube to the water / Havoline mixture at 130 ° C. is 60 g / (m 2 / 24h).

  EXAMPLE 2 Comparative A 1.5 mm thick, 12 mm outer diameter tube made of AESN P110 TL was extruded on a McNeil line at 230 ° C. This tube was tested in pendulum impact according to DIN 73378 with a 7.5J pendulum. does not break at 23 C or -30 C.

  After 300 hours of the aging described in Example 1, the pendulum impact tested tube breaks brittle at -30 C but also at 23 C.

  The permeability of this single-layer tube to the water / Havoline mixture at 130 ° C. is 260 g / (m2.24h).

  Example 3 Comparative In the Werner 40 extruder, a mixture of Kynar 720 (20% by weight), with 50% of Kynar ADX 120 and 30% of Paraloid was made at 230 ° C. A three-layer tube of thickness 1.5 mm and outside diameter 12 mm composed of an outer layer of AESN P110 TL (1250 μm), NECHVO (50 μm) and the preceding PVDF alloy layer was extruded on a McNeil line at 230 [deg.] C. internal (200pm).

  This tube tested pendulum shock according to DIN 73378 with a pendulum of 7.5J does not break at 23 C nor at -30 C.

  After 300 hours of the aging described in Example 1, the test tube in pendulum shock breaks brittle at -30 C, but does not break at 23 C.

  The permeability of this bilayer tube to the water / Havoline mixture at 130 ° C. is 130 g / (m 2 / 24h).

Claims (10)

  A multilayer pipe comprising in its radial direction from the outside to the inside: an outer layer (1) of polyamide, an inner layer (2) of a composition comprising, the total being 100%: 5 to 30% by weight of a mixture (A) comprising: a polyethylene bearing epoxy functional groups, an impact modifier selected from elastomers and very low density polyethylenes, said impact modifier being wholly or partly functionalized, at 70% by weight of a mixture (B) comprising: a fluorinated polymer (B1), a functionalized fluoropolymer (B2), the proportion of (B1) is between 1 and 60% by weight of (A) + (B), the layers being successive and adhering between them in their respective contact area.   2 tube according to claim 1 wherein a layer (3) of polyolefin is disposed on the side of the layer (2) and this layer (3) becomes the inner layer.   Tube according to any one of the preceding claims wherein the polyamide of the outer layer (1) is an amine terminated polyamide or comprising more amine terminations than acid termini.   A tube according to any one of the preceding claims wherein there is disposed between the outer layer (1) and the layer (2) an amino-terminated polyamide layer or comprising more amine terminations than acid terminations.   A tube according to any one of the preceding claims wherein the impact modifier of the mixture (A) is a maleic anhydride grafted EPR or maleic anhydride grafted EPDM.   Tube according to any one of the preceding claims, in which the functionalized fluoropolymer (B2) is a PVDF homopolymer or copolymer grafted with maleic anhydride.   Tube according to any one of the preceding claims wherein the fluoropolymer (B1) is a PVDF homopolymer or copolymer.   8 tube according to any one of the preceding claims wherein the proportions of (A) are 5 to 10% for respectively 95 to 90% of (B).   Tube according to any one of the preceding claims wherein the proportion of polyethylene carrying epoxy functions is from 1 to 2 parts per 5 parts of the impact modifier.   Tube according to any one of the preceding claims wherein the proportion of (BI) is between 35 and 60% by weight of (A) + (B).   Tube according to any one of the preceding claims wherein the proportion of (BI) is between 45 and 55% by weight of (A) + (B).   12 Use of the tubes according to any one of the preceding claims for the transport of the cooling liquid.