EP0822012B1 - Coating on metallic surfaces and use on tubes and cables - Google Patents

Abstract

Coated metallic surface comprises, successively from metal, at least one layer of polyurethane; and at least one layer of thermoplastic polymer; with a binder between the two layers. Also claimed is method for coating surface and device comprising bundle of steel strands with the coating.

Description

The present invention relates to a metal surface coating and its application to tubes and cables, it relates more particularly to a coating successively comprising, starting from the metal, a layer of polyurethane and a layer of thermoplastic polymer, an adhesion binder can be placed between the polyurethane and the thermoplastic polymer.

• qui présente une bonne adhérence, qu'on peut traduire par exemple par la force de pelage,
• qui présente une bonne résistance au cisaillement (c'est-à-dire aux efforts axiaux),
• qui présente une bonne flexibilité et une bonne élasticité,
• qui résiste à la corrosion.

The object of the invention is a coating:

• which has good adhesion, which can be translated for example by the peel strength,
• which has good resistance to shear (that is to say to axial forces),
• which has good flexibility and good elasticity,
• which resists corrosion.

The present invention is useful for example for coating the surface outside of pipes, to coat electrical or telephone cables or metal cables such as guy wires.

DE 3,422,920 describes coatings for steel pipes successively comprising a layer of epoxy resin, a layer of grafted polypropylene and finally an outer layer of a mixture of polypropylene and a polypropylene / polyethylene block copolymer. The glass transition temperature (T _g ) of the epoxy resin is between 80 and 94 ° C. These coatings are suitable for hot water at 90 ° C.

Re 30 006 describes coatings of steel pipes comprising successively an epoxy resin and a polyethylene modified by grafting or copolymerization with maleic anhydride.

Epoxy resins are not flexible enough and are not perfect for protection against humidity.

EP 185,058 describes telecommunication cables coated by polyurethanes for protection against humidity, but these cables have no thermoplastic coating.

The coatings of the invention thanks to this shear strength have a very high cohesion, thus for an electric cable which must resist the efforts of its own weight or support the weight of boxes of connection or other instruments, it is necessary that the forces transmitted by through the thermoplastic polymer layer can be spread throughout the cable including the metallic core. It also helps that when connection of two electric cables, the connection box can lean on the external coverings of the two cables to be connected without that this results in a decohesion inside the cable and thus the forces such as the tensile forces on the cables can be transmitted. It is then possible make the connection by stripping the cable only to the minimum. Cables must also withstand winding, which is why it is important that the coating according to the present invention has good flexibility.

The same is true for metallic cables which can transmit efforts by their coating.

The invention is useful for strands that are individually protected from suspended civil engineering works.

We know of individually protected strands comprising several wires of twisted steel surrounded by an outer sheath of flexible plastic, the twisted steel wires leaving spaces inside this sheath interstitials that are filled with a protective material.

These individually protected strands are usually used for make deck stays, and they have proven to be particularly effective to protect these shrouds against corrosion.

The protective material used in these individually protected strands of the prior art is generally constituted by wax or fat, so these individually protected strands cannot effectively transmit significant axial forces from their outer sheath towards their twisted steel wires.

This is the reason why such individually protected strands do not cannot be used to make the supporting cables for suspension bridges, of hanging blankets, or other suspended works, because such cables wearers must resume frictionally directed efforts parallel to their axis, forces which are transmitted by cable ties to which a structure of civil engineering is suspended by lines.

In suspension bridges or suspended roofs, we therefore have recourse to load-bearing cables formed by bundles of bare strands or strands of steel. These carrying cables are surrounded by an outer protective layer which can be made up of paint, bitumen or a tubular sheath, but this protective layer is interrupted at the level of the collars, tightened directly on steel.

• les colliers doivent être très fortement serrés sur les câbles porteurs, d'une part compte tenu de la médiocrité du coefficient de frottement acier sur acier et, d'autre part pour limiter les mouvements relatifs entre les brins d'acier, générateurs d'usure et de fatigue par "fretting corrosion" (également appelée "fatigue induite par petits débattements" ou "usure induite par petits débattements") : ce serrage intense nécessite des colliers très longs (par exemple jusqu'à 2 mètres) et massifs, serrés par de nombreux boulons,
• les phénomènes de fatigue par "fretting corrosion" ne sont jamais complètement évités, ce qui entraíne à la fois un desserrage des colliers et la rupture des brins constitutifs du câble porteur,
• et les phénomènes de corrosion chimique sont extrêmement fréquents.

This configuration has the following serious drawbacks:

• the collars must be tightened very tightly on the supporting cables, on the one hand taking into account the poor coefficient of friction steel on steel and, on the other hand to limit the relative movements between the steel strands, generators of wear and fatigue by "fretting corrosion" (also called "fatigue induced by small deflections" or "wear induced by small deflections"): this intense tightening requires very long collars (for example up to 2 meters) and massive, tightened by many bolts,
• the phenomena of fatigue by "fretting corrosion" are never completely avoided, which leads to both loosening of the collars and the breaking of the strands constituting the carrying cable,
• and chemical corrosion phenomena are extremely frequent.

The prior art FR 2739113 has proposed coating the strand and filling the spaces between the metal wires with polybutadiene then coat the strand a polyethylene sheath by placing a grafted polyethylene to reinforce the bond between polybutadiene and the polyethylene sheath.

Thanks to this arrangement, the axial forces are effectively transmitted from the outer sheath of the strand to its twisted steel wires, both by surface adhesion and shape adhesion of polybutadiene to the sheath exterior and on twisted steel wires, and by resistance of polybutadiene to shear.

In addition, when using such individually protected strands for constitute the carrying cables of a bridge or other suspended structure, it is no longer necessary to tighten the line collars as hard as in the prior art, due to the fact that the sheaths of the individually protected strands have a good coefficient of friction.

In addition, the phenomena of fatigue by "fretting corrosion" are avoided since there is no longer direct contact between the steel wires from one strand to another.

Finally, a carrying cable made up of strands according to the invention resists perfectly to chemical corrosion.

However, polybutadiene must be vulcanized to present good resistance to aging and keep an elastomeric character to avoid penetration of water into the strands while continuing to provide the connection mechanical with polyethylene sheath.

Once vulcanized polybutadiene is no longer thermoplastic, it is necessary so vulcanize it after having coated the strand which is very complicated. The coating of the present invention is much simpler, the polyurethane forms during coating of the metal surface, it adheres better to the surface metallic, is perfectly hydrophobic and fills the entire space perfectly between the bundles of bare strands or strands of steel. The present invention also relates to the device comprising these bundles of strands or strands of coated steel forming a cable and surrounded by a metal collar made of two substantially hemicylindrical shells which are tightened around the cable at the by means of bolts, said collar is provided with at least one hook.

The present invention is therefore a coated metal surface comprising successively starting from the metal at least one layer of polyurethane, and at least a single layer of polymer thermoplastic, a binder that can be placed between the polyurethane and the thermoplastic polymer, said polyurethane resulting from the reaction of at least one polyol with at least one polyisocyanate and optionally at least a chain extender, said polyol being chosen from polydienepolyols.

The metal surface can for example be an electric cable, telephone, the outside surface of a pipe, or a guy wire. Regarding cables or shrouds the metal part can be of circular section or be a set of cables with circular cross-section as usual in cables cables or guy lines.

By shroud is meant metallic cables used for their tensile strength and generally formed of several cross-section elements which are twisted. Their diameter can be from a few millimeters to several centimeters. Several cables formed of twisted elements can themselves be brought together to form a single shroud.

The metal can be steel, copper, aluminum, zinc, stainless steel or their alloys or even galvanized steel.

The surface can therefore be either a simple surface like the surface outside of a pipe either the result of several twisted elements or the assembly of cables formed themselves from several twisted elements. This surface is therefore covered with at least one layer of polyurethane.

Advantageously, the polyurethane is placed so as to cover the whole surface or surfaces of the different elements and that we obtain essentially a cylinder whose outer surface is polyurethane. The advantage of polyurethane is that it covers metals well and that in the case complex surfaces like twisted elements, it penetrates the heart of cable or guy line. Hydrophobic polyurethanes are preferably used. These polyurethanes are resistant to aqueous acidic, basic or saline and hydrolysis. They have good electrical insulation, adhere to metals and retain a certain flexibility between - 65 ° C and + 100 ° C. polyurethanes result from the reaction of at least one polyol with at least one polyisocyanate and possibly a chain extender.

The polyols which can be used according to the present invention can be chosen among the polyester polyols, the polyether polyols, the polythioether polyols, the polyacetals-polyols, polycarbonates-polyols, polyestamides-polyols, polyamide polyols, polydien polyols and the mixture of at least two of the aforementioned polyols.

By way of polyesters bearing hydroxy groups, mention will be made of the products reaction of polyvalent alcohols, preferably divalent, accompanied optionally trivalent alcohols, and polyvalent carboxylic acids, and preferably divalent. Instead of free polycarboxylic acids, one can also use in the preparation of polyesters the acid anhydrides corresponding polycarboxylic acids or esters of polycarboxylic acids and corresponding lower alcohols or mixtures thereof. Acids polycarboxylics can be aliphatic, cycloaliphatic, aromatic and / or heterocyclic and optionally substituted, for example by halogen atoms, and / or saturated.

By way of illustration of such carboxylic acids and derivatives, mention will be made of: succinic, adipic, suberic, azelaic, sebacic, phthalic acids, trimellitic, phthalic, tetrahydrophthalic, hexahydrophthalic anhydrides, tetrachtorophthalic, endomethylene-tetrahydrophthalic, glutaric, acid maleic, maleic anhydride, fumaric acid, unsaturated fatty acids dimerized and trimerized optionally as a mixture with fatty acids unsaturated monomers such as oleic acid; dimethyl terephthalate and bis-glycol terephthalate.

Among the polyvalent alcohols, there may be mentioned, for example, 1,2-ethanediol, 1,2-and1,3-propanediol, 1,4-and 2,3-butanediol, 1,6-hexanediol, 1,8-octanediol, neopentyl glycol, 1,4-bis-hydroxymethylcyclohexane, 2-methyl-1,3-propanediol, glycerol, trimethylolpropane, 1,2,6-hexanetriol, 1,2,4-butane-triol, trimethylolethane, pentaerythritol, quinitol, mannitol, sorbitol, formitol, methylglucoside, and also diethylene glycol, triethylene glycol, tetra-ethylene glycol and higher polyethylene glycols, dipropylene glycol and higher propylene glycols and dibutylene glycol and higher polybutylene glycols. Polyesters can carry groups carboxyl in certain terminal positions. You can also use polyesters of lactones, for example epsilon-caprolactone, or acids hydroxycarboxylic, for example omega-hydroxycaproic acid.

The polyether polyols which can be used according to the invention carrying at least 2, in general 2 to 8, preferably 2 to 3 hydroxy groups, are those of the type known per se which are obtained for example by polymerization of epoxides such as oxide ethylene, propylene oxide, butylene oxide, tetrahydrofuran, styrene oxide or epichlorohydrin on themselves, for example in the presence of Lewis catalysts such as BF ₃ , or by addition of these epoxides, preferably ethylene oxide and propylene oxide, optionally as a mixture or successively, on starting components carrying reactive hydrogen atoms such as water, alcohols, ammonia or amines, for example 1,2-ethanediol, 1,3 or 1,2 propaneediol, trimethylolpropane, glycerol, sorbitol, 4,4'-dihydroxydiphenylpropane, aniline, ethanolamine or ethylene- diamine. Polyethers of sucrose or polyethers condensed on formitol or on formose can also be used in accordance with the invention. In many cases, polyethers containing preponderant proportions (up to 90% by weight, relative to all the OH groups present in the polyether) of primary OH groups are preferred.

By way of polythioters-polyols, mention will be made in particular of the products of condensation of thiodiglycol on itself and / or on other glycols, acids dicarboxylics, formaldehyde, and aminocarboxylic acids or amino alcohols. Depending on the nature of the second component, the products obtained are for example mixed polythioethers, polythioether esters or polythioether ester amides.

By way of illustration of polyacetal polyols, mention will be made, for example, of those which can be prepared from glycols such as diethylene glycol, triethylene glycol, 4,4'-dihydroxyethoxydiphenyldimethylmethane, hexane-diol and formaldehyde. Polyacetals can also be used in the invention obtained by polymerization of cylindrical halves such as, for example, trioxane.

By way of illustration of polycarbonates carrying hydroxy groups, we cite those of known type which are obtained for example by reaction of diols such as propane-diol-1,3, butane-diol-1,4 and / or hexane-diol-1,6, diethylene glycol, triethylene glycol, tetraethylene glycol or thiodiglycol, with diaryl carbonates, for example diphenyl carbonate, or phosgene;

By way of illustration of polyesteramides-polyols and polyamides-polyols, we cite for example the mainly linear condensates obtained from saturated or unsaturated polyvalent carboxylic acids and their anhydrides and saturated or unsaturated polyvalent amino alcohols, diamines, polyamines and their mixtures.

It is also possible to use polyols already containing groups urethane or urea, as well as possibly modified natural polyols such as Castor oil.

By way of illustration of polydien-polyols which can be used according to the present invention, mention will be made of the hydroxytelechelic conjugated diene oligomers which can be obtained by different processes such as polymerization conjugated diene radical having 4 to 20 carbon atoms in the presence a polymerization initiator such as hydrogen peroxide or a compound azo such as azobis-2,2 '[methyl-2, N- (hydroxy-2ethyl) propionamide] or anionic polymerization of conjugated diene having 4 to 20 carbon atoms in the presence of a catalyst such as naphthalene dilithium.

According to the present invention, the conjugated diene of the polydiene-polyol is chosen from the group comprising butadiene, isoprene, chloroprene, 1,3-pentadiene, cyclopentadiene. The number-average molar mass of polyols which can be used can vary from 500 to 15,000 and preferably from 1000 to 3000.

et 15 à 30 % de préférence 20 % de motifs

According to the present invention, a polydiene polyol based on butadiene is preferably used. Advantageously, the polydiene glycol comprises 70 to 85% by mole, preferably 80% of units

and 15 to 30% preferably 20% of patterns

Also suitable are copolymers of conjugated dienes and vinyl and acrylic monomers such as styrene, acrylonitrile.

We would not go outside the invention if we used oligomers epoxidized butadiene hydroxytelechelics on the chain or even hydroxytelechelic hydrogenated oligomers of conjugated dienes.

According to the present invention, the polydien-polyols can have number average molecular weights at most equal to 7000 and preferably between 1000 and 3000.

The OH index expressed in mlq / g is between 0.5 and 5, their viscosity is between 1000 and 10 000 M.Pa.s.

By way of illustration of polydien-polyols, mention will be made of polybutadienes with hydroxylated terminations marketed by the company ELF ATOCHEM S.A. under the names Poly Bd®R45 HT and Poly Bd®R20 LM.

Mixtures of the above-mentioned compounds can be used such as, for example, mixtures of polyether polyols and of polydienes polyols.

It would not go beyond the scope of the invention if polyamine compounds having a number average molecular mass were used mn between 500 and 5000.

By way of illustration of such compounds, mention will be made of polyoxypropylenes terminated by NH2 functions, polyoxytetramethylenes and polybutadienes terminated by NH 2 functions, the butadiene / styrene copolymers and butadiene / acrylonitrile terminated by NH2 functions.

By chain extender, we currently designate compounds bearing at least two reactive functions with the isocyanate functions.

As examples of such reactive functions, mention will be made of the functions hydroxyl and amine functions.

According to the invention, the chain extender can be chosen from polyols. Their molecular mass can be between 62 and 500.

By way of illustration of such compounds, mention will be made of ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, 2-ethyl-1,3-hexanediol, N, N bis (2-hydroxypropyl) aniline, 3-methyl-1,5-pentanediol and the mixture of at least two of the above-mentioned compounds.

Polyamines can also be used as chain extenders. Their molecular mass can be between 60 and 500.

By way of illustration of such polyamines, mention will be made of ethylene diamine, diphenyl methane diamine, isophoronediamine, hexamethylenediamine, diethyltoluenediamine.

At least part by weight of one or more extenders of aforementioned chain for 100 parts by weight of polyol used and, from preferably 5 to 30 parts by weight.

We can add a catalyst which can be chosen from the group including tertiary amines, imidazoles and compounds organometallics.

By way of illustration of tertiary amines, mention may be made of 1,4-diaza bicyclo [2.2.2] octane (DABCO).

By way of illustration of organometallic compounds, mention may be made of tin dibutyldilaurate, tin dibutyldiacetate.

The amounts of catalyst can be between 0.01 and 5 parts by weight per 100 parts by weight of polyol.

The composition according to the invention may also contain fillers inert and various additives such as antioxidants, anti U-V.

According to the present invention, the polyisocyanate used can be a aromatic, aliphatic or cycloaliphatic polyisocyanate having at least two isocyanate functions in its molecule.

By way of illustration of an aromatic polyisocyanate, mention will be made of 4,4'-diphenyl-methane diisocyanate (MDI), liquid modified MDI, MDI 2,4- and 2,6-toluylene diisocyanate (TDI) and their mixture, xylylene diisocyanate (XDI), triphenylmethane triisocyanate, tetramethylxylylene diisocyanate (TMXDI), paraphenylene diisacyanate (PPDI), naphthalene diisocyanate (NDI).

Among the aromatic polyisocyanates, the invention relates to preferably 4,4'-diphenylmethane diisocyanate and especially MDI modified liquids.

By way of illustration of an aliphatic polyisocyanate, mention will be made hexamethylene diisocyanate (HMDI) and its derivatives, trimethylhexamethylene diisocyanate.

As an illustration of cycloaliphatic polyisocyanate, mention will be made isophorone diisocyanate (IPDI) and its derivatives, 4,4'-dicyclohexylmethanediisocyanate and cyclohexyl diisocyanate (CHDI).

We would not go beyond the scope of the invention if we used isocyanate prepolymers obtained by reaction of a mentioned polyisocyanate previously with a polyol such as in particular polyether-polyol, polyester-polyol and polydiene-polyol or with a polyamine.

Advantageously, the isocyanates are used in such amounts that the NCO / OH molar ratio is between 0.3 and 2 and, preferably, between 0.5 and 1.2.

The NCO / OH molar ratio must be calculated taking into account the presence of reactive functions with isocyanate functions, such as hydroxyl and / or amine functions, of the chain extender.

One can also add in the formulation of polyurethane, that is to say in the mixture of different ingredients before or during the polymerization, adhesion promoters such as functional silanes. ie products having a trialcoxysilane end and an organic function such as amine, epoxy or vinyl, coupling agents such as acids or unsaturated carboxylic acid anhydrides and mineral fillers such as calcium carbonate, anti-bubble agents, anti U.V., sieves molecules, anti-corrosion pigments and flame retardants.

The possible binder is any product which makes it possible to adhere the layer of polyurethane and the thermoplastic polymer layer while giving a cohesion to the whole as explained above unless the polymer has good adhesion to polyurethane.

Advantageously, functionalized polyolefins are used.

• le polyéthylène, le polypropylène, les copolymères de l'éthylène et d'au moins une alpha oléfine, des mélanges de ces polymères, tous ces polymères étant greffés par des anhydrides d'acides carboxyliques insaturés tels que par exemple, l'anhydride maléique. On peut aussi utiliser des mélanges de ces polymères greffés et de ces polymères non greffés.
• les copolymères de l'éthylène avec au moins un produit choisi parmi (i) les acides carboxyliques insaturés, leurs sels, leurs esters, (ii) les esters vinyliques d'acides carboxyliques saturés, (iii) les acides dicarboxyliques insaturés, leurs sels, leurs esters, leurs hemiesters, leurs anhydrides, éventuellement les epoxydes insaturés à condition que le copolymère ne contienne pas de fonction acide ; ces copolymères pouvant être greffés ou copolymérisés.

By way of example of a binder, there may be mentioned:

• polyethylene, polypropylene, copolymers of ethylene and 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. It is also possible to use mixtures of these grafted polymers and of these non-grafted polymers.
• copolymers of ethylene with at least one product chosen from (i) unsaturated carboxylic acids, their salts, their esters, (ii) vinyl esters of saturated carboxylic acids, (iii) unsaturated dicarboxylic acids, their salts, their esters, their hemiesters, their anhydrides, possibly the unsaturated epoxides provided that the copolymer does not contain an acid function; these copolymers can be grafted or copolymerized.

Polyolefins grafted with anhydride are advantageously used maleic.

• éthylène / (méth)acrylate d'alkyle / epoxyde insaturé tel que le (méth)acrylate de glycidyle ;
• éthylène / acétate de vinyle / anhydride maléique ou acide acrylique ;
• éthylène / acétate de vinyle / epoxyde insaturé tel que le (méth)acrylate de glycidyle ;
• (éthylène / acétate de vinyle) greffé par l'anhydride maléique, l'acide acrylique ou un epoxyde insaturé ;
• (éthylène / (méth)acrylate d'alkyle) greffé par l'anhydride maléique, l'acide acrylique ou un epoxyde insaturé.

By way of illustration of such copolymers, mention may be made of ethylene / alkyl (meth) acrylate / maleic anhydride or acrylic acid copolymers.

• ethylene / alkyl (meth) acrylate / unsaturated epoxide such as glycidyl (meth) acrylate;
• ethylene / vinyl acetate / maleic anhydride or acrylic acid;
• ethylene / vinyl acetate / unsaturated epoxide such as glycidyl (meth) acrylate;
• (ethylene / vinyl acetate) grafted with maleic anhydride, acrylic acid or an unsaturated epoxide;
• (ethylene / (meth) acrylate) grafted with maleic anhydride, acrylic acid or an unsaturated epoxide.

The thickness of this binder layer can be between 15 and 500 µm.

As for the layer of thermoplastic polymer, it may be by example of a polyamide, a polyolefin, a fluoropolymer, a resin styrenic or polyester.

The polyamide can be PA-6, PA-6.6, PA-11, PA-12.

The polyolefin can be a polyethylene, a copolymer of ethylene and of an alpha olefin, a homo or copolymer polypropylene, a copolymer of ethylene and a vinyl ester of saturated carboxylic acid.

The fluoropolymer can be PVDF.

The styrenic resin can be polystyrene.

The polyester can be PET or PBT.

Advantageously, high density and medium polyethylenes are used density.

The thermoplastic polymer may also contain a product which facilitates adhesion to polyurethane. This product can be the thermoplastic polymer grafted or the binder mentioned above.

The thickness of this layer of thermoplastic polymer is a function of desired properties, they can be between 1 and 30 mm.

The present invention also relates to a method for manufacturing these coated surfaces in which the polyurethane is deposited, before the end of the polymerization, on the metal surface then the polymerization is completed optionally by heating, the outer surface of the layer of polyurethane then we cover it with the thermoplastic polymer and then we cools. The deposition of the polyurethane layer depends on the nature of the metal surface. If this is the outside surface of a steel pipe, we will advantageously proceed to a degreasing then a sandblasting unless the surface is not already galvanized. The same is true for cables such as wire. Polyurethane is in the form of at least two parts liquids which are mixed at the time of application on the metal surface. One part contains the polyol, the other isocyanate, the third possibly the catalyst. The other ingredients are divided between parts, depending on their responsiveness and compatibility. We operate advantageously at room temperature for example between 10 and 50 ° C. But we would not get out of the framework of the invention if one operated at 60 or 80 ° C. Generally, the reaction between polyol, polyisocyanate and chain extender takes place between 50 and 80 ° C in a few minutes. It would not go beyond the scope of the invention to use a monocomponent polyurethane powder system with thermal activation.

We therefore proceed to coating the metal surface with the polyurethane then when the surface is well coated, it is heated to polymerize. For example, for the outer surface of a pipe, we deposit the polyurethane (before polymerization) by coating or rolling, or by a flat die producing a continuous ribbon which is wrapped around the tube by the rotation of the tube on himself. For an electric cable or a shroud, one can proceed by a annular die which deposits the mixture of the two parts around the cable or the guy. If it is several twisted elements, we proceed in the same way making sure to fill all the gaps between the different elements. Layer polyurethane being deposited and polymerized, we then proceed to deposit the optional layer of binder and thermoplastic polymer. advantageously, after the polyurethane is completely polymerized, that is to say that we have reached the so-called "sticky" time, we heat its outer surface for example by a heating or induction tunnel at a temperature of around 30 or 40 ° C lower than that of extrusion of the binder then the binder and the polymer are deposited thermoplastic, either by coextrusion in annular dies for small tube diameters or for cables and shrouds either by flat dies producing ribbons that are rolled up. Then cooling is carried out. the water.

Examples

• PolyBd®R45 HT polybutadiène hydroxylé de Mn égale à 2800 (déterminée par chromatographie d'exclusion stérique), présentant un indice d'hydroxyle I_OH exprimé en milliéquivalent par gramme (meq/g) égal à environ 0,83, une viscosité en m.Pa.s (cp) à 30°C égale à 5000 et une densité égale à 0,90 ;

Voranol RA 100 : désigne un polyether polyol de Mn .:209, de nombre d'hydroxy 530 mg KOH/g, de viscosité 900 à 1 500 m. P.a.s et densité 1,055 à 25 °C.

Carbonate de calcium : OMNYA 90 T désigne un produit de granulométrie diamètre moyen 1,1 µm.

Silane A 187 : désigne un gamma-glucidoxypropyltrimetoxysilane liquide de densité 1,09 à 250 °C et poids moléculaire 236.

Isonate 143 M : désigne un.diisocyanate de diphenylruethane modifié de viscosité 30 poises de densité à 25 °C, 1,210 et NCO 29,4 %.

OREVAC 1 :

désigne un mélange de copolymère de copolymères éthylène alphaloléfine greffés par de l'anhydride maléique de MFi.1 à 190° C 2,16 kg et contenant 0,5 % en poids d'anhydride maléique.

PEHD :

est un polyéthylène haute densité (TUB 71 de SOLVAY).

The following products are used:

• PolyBd ® R45 HT hydroxylated polybutadiene of mn equal to 2800 (determined by size exclusion chromatography), having a hydroxyl index I _OH expressed in milliequivalents per gram (meq / g) equal to approximately 0.83, a viscosity in m.Pa.s (cp) at 30 ° C equal to 5000 and a density equal to 0.90;

Voranol RA 100 : designates a polyether polyol of mn .: 209, number of hydroxy 530 mg KOH / g, viscosity 900 to 1500 m. Pitch and density 1.055 at 25 ° C.

Calcium carbonate : OMNYA 90 T designates a product with an average particle size of 1.1 µm.

Silane A 187 : denotes a liquid gamma-glucidoxypropyltrimetoxysilane with a density of 1.09 at 250 ° C and molecular weight 236.

Isonate 143 M : denotes a modified diphenylruethane diisocyanate with a viscosity of 30 poise, density at 25 ° C., 1.210 and NCO 29.4%.

OREVAC 1:

denotes a mixture of copolymer of ethylene alphalolefin copolymers grafted with maleic anhydride of MFi.1 at 190 ° C. 2.16 kg and containing 0.5% by weight of maleic anhydride.

HDPE:

is a high density polyethylene (TUB 71 from SOLVAY).

Example 1 : the following polyurethane formulation is prepared.

• Polyol: PolyBd®R45 HT 100 g
• Maleic anhydride 1 g
• Chain extender (short polyol): Voranol RA 100 17.5 g
• Filler: calcium carbonate: Omnya 90 T 100 g
• adhesion promoter: epoxy silane: Silane A 187 1.1 g
• Isonate 143 M (NCO / OH = 1.05) 36 g

It is obtained by mixing a first part containing the polyol, the chain extender, the carbonate the silane and the MAH and of a second part containing isocyanate.

The first part is homogenized and degassed under vacuum (1 hour, 80 ° C at 1,360 Pa absolute pressure). Then we mix the two solutions and the mixture is placed at room temperature (20 ° C) on the exterior surface a galvanized steel pipe with an outside diameter of 115, a thickness of 6.5 mm, length. 3 m.

Then let it crosslink.

The thickness of the polyurethane layer is 0.5 to 1 mm.

Using an induction furnace, the tube thus coated is heated polyurethane at 180 ° C-190 ° C then covered with a layer of binder (OREVAC 1) 200 to 300 µm thick then a layer of 2.50 to 3 mm of HDPE. The binder and HDPE are each deposited by a flat die producing a ribbon continuous that is wrapped around the tube by the rotation of the tube on itself. The tube coated is then cooled with water for 5 minutes.

Peel tests at a temperature of 23 ° C according to the standard DIN 30670 were realized. On a sample extracted from a coated galvanized steel tube and whose heating temperature before coating by the binder and HDPE by induction was around 190 ° C (± 5 ° C), we obtained a force of average coat of 175 N / cm. The rupture is cohesive in polyurethane.

Claims (7)

1. Coated metal surface including successively, starting at the metal, at least one layer of polyurethane and at least one layer of thermoplastic polymer, it being possible for a binder to be placed between the polyurethane and the thermoplastic polymer, said polyurethane resulting from the reaction of at least one polyol with at least one polyisocyanate and optionally with at least one chain extender, said polyol being chosen from polydienes-polyols.
2. Coated metal surface according to claim 1, chosen from the external surface of pipes, cables or assemblies of twisted cables of stay wires, electrical cables and telecommunications cables.
3. Coated metal surface according to claim 2, in which said polyol is a polybutadiene with hydroxyl ends.
4. Coated metal surface according to any one of claims 1 to 3, in which the binder is a polyolefin grafted with maleic anhydride.
5. Coated metal surface according to any one of claims 1 to 4, in which the layer of thermoplastic polymer is chosen from polyamides, polyolefins, fluoropolymers, styrene-based resins and polyesters.
6. Process for the manufacture of the coated surface of any one of claims 1 to 5, in which the polyurethane is deposited before the end of the polymerization on the metal surface and the polymerization is then finished optionally by heating, the external surface of the layer of polyurethane is heated and is then covered optionally with the binder and then the thermoplastic polymer and subsequently cooling is carried out.
7. Device including bundles of wires or of steel strands which have a coating according to one of claims 1 to 5 and which form a cable and are surrounded by a metal clamp consisting of two substantially hemicylindrical shells which are tightened around the cable by means of bolts, the said clamp being provided with at least one hook.