Clad pipeline

The present invention relates to the use of metal conduits whose surface is coated with a polyamide layer for producing conduits laid without excavation or sand layers, as well as conduits thus produced.

Metal supply tubes, processing tubes or manufacturing tubes are currently coated with, for example, polyolefins, such as polyethylene or polypropylene (WO2002 / 094922; US2002 / 0066491; EP-A-0346101). The coating or jacket acts primarily on anticorrosion; the coating or coating is described by the corresponding standard. For polyolefin jackets, the standard is, for example, DIN EN 10288 to DIN 30678. For polyolefin jackets, the layer is produced, for example, by tube extrusion or screw extrusion. Epoxy-and an adhesive layer can be applied in sequence prior to extrusion to promote adhesion.

Other prior art specified by DIN EN 10310 (German version EN 10310: 2003) envisions coating steel pipes with polyamide powder for conduits laid underground or in water. The polyamide coating is applied by immersion in a fluid layer, spraying, or by roller coating. Restricted by the method, only a relatively thin layer can be applied on the metal when using a powder coating, such a layer is unsuitable for non-excavation laying of conduits. In particular, it is disadvantageous that powders from relatively low molecular weight polyamides must be used for coating to ensure good fluidity of the melt on hot metal surfaces. The coating thus obtained has insufficient mechanical strength; the layer acts in anticorrosion in the first place. In particular, it is also disadvantageous that it is not possible to apply the polyamide layer to the tube already containing the coating from the polyolefin or adhesion accelerator layer as described above.

In addition, epoxide-or polyurethane-based thermosetting resin coatings are also known; the coating acts only on anticorrosion and does not provide any protection against mechanical damage. For example, in the case of plow work-, drilling-or laying without a sand layer by the press-fitting method or non-cutting laying, the corrosion resistance exhibited by the prior art is insufficient in mechanical resistance. Impact during laying-or frictional loading partially damages the polymer layer and causes the metal to come into contact with water. The resulting corrosion significantly reduces the life of the conduit. For example, the same applies to the mechanical load caused by an unintended collision of the dredging excavator in the repair work in the later operation. A conduit with such an anticorrosive coating must be embedded in a rock-free material. In the prior art, conduits so coated or with a jacket are often protected from mechanical damage by an additionally applied cement mortar jacket.

The application of the cement mortar layer is carried out in a separate working process. After application of the mortar layer, the layer must be cured for at least 5 days, after which the tube can be further handled. Therefore, the process is extremely time consuming and, by extension, costly. Prior arts relating to mortar jackets are found, for example, in the following references: US5580659, DE4208047C1, DE4201113C1, DE3305158A1, US4454172 and US4361336. In Japan, the DVGW Working Sheet GW340 stipulates requirements for cement mortar jackets. However, this type of mortar layer increases the mass of the tube not a little, which makes it more difficult to handle. It also reduces the mass-dependent loading capacity of transportation vehicles.

Therefore, the subject of the present invention is that metal pipes are effectively protected against corrosion during mechanical loads, for example during non-excavation or laying without sand layers, because the integrity of the coating is maintained without additional protective measures. It was to provide a coated metal conduit to be made. In addition, it is desirable to achieve a firm adhesion to the tubing or the coating that may be present on the tubing. As a whole, it is desirable to provide a tube that is easy to handle and can be manufactured at low cost.

The above and other issues obvious from the present application are solved by the use of metal conduits for making conduits that are laid underground without excavation and / or sand layers, where the tubes are polyamide molding materials. Covered with an extruded layer from.

The concept of "underground" also includes laying at the bottom of the body of water, for example on the seabed.

The pipe consists of, for example, steel, specialty steel, copper, aluminum, cast iron, galvanized steel, metal alloys, for example GALFAN coated steel or other metals. The tube can be manufactured by any method of the prior art.

Polyamides can be made from ω-aminocarboxylic acids or corresponding lactams from combinations of diamines and dicarboxylic acids. In principle, all polyamides, such as PA46, PA6, PA66, or copolyamides based on units derived from terephthalic acid and / or isophthalic acid (commonly referred to as PPA) can be used. .. In one advantageous embodiment, the monomer unit has an average of at least 8, at least 9 to at least 10 C atoms. Here, in the case of a mixture of lactams, the arithmetic mean is taken into consideration. In the case of a combination of diamine and dicarboxylic acid, the arithmetic mean of the C atoms of the diamine and dicarboxylic acid must be at least 8, at least 9 to at least 10 in the advantageous embodiment described above. Suitable polyamides can be made from, for example: PA610 (hexamethylenediamine [6C atoms] and sebacic acid [10C atoms], so the average of C atoms in the monomeric unit is 8 here), PA88 (octamethylene). Can be made from diamine and 1,8-octanedioic acid), PA8 (can be made from capryllactam), PA612, PA810, PA108, PA9, PA613, PA614, PA812, PA128, PA1010, PA10, PA814, PA148, PA1012, PA11, PA1014, PA1212 and PA12. The production of polyamide is a prior art. As a matter of course, a copolyamide based on this can also be used, and in this case, a monomer such as caprolactam can be used in combination.

The polyamide may be a polyether ester amide or a polyether amide. Polyetheramides are, in principle, known from, for example, DE-OS3006961. The polyether amide contains a polyether diamine as a comonomer. Suitable polyether diamines are available by converting the corresponding polyether diols by reductive amination or binding to acrylonitrile and subsequent hydrogenation (eg EP-A-0434244; EP-A- 0296852). Polyetherdiamines usually have a number average molecular weight of 230-4000 and their proportion in the polyetheramide is advantageously 5-50% by weight.

A commercially available polyether diamine derived from propylene glycol is JEFFAMIN from Huntsman.^(R)Commercially available as D type. In principle, a polyether diamine derived from 1,4-butanediol or 1,3-butanediol, or, for example, a mixed composition of polyether diamines having a random or block-like distribution of units derived from the diol is also sufficient. Suitable for.

Similarly, a mixture of various polyamides can be used, subject to sufficient compatibility. Compatible polyamide combinations are known to those of skill in the art; examples thereof include combinations of PA12 / PA1012, PA12 / PA1212, PA612 / PA12, PA613 / PA12, PA1014 / PA12 and PA610 / PA12. In case of doubt, compatibility combinations can be examined by routine testing.

In one advantageous embodiment, in a narrow sense, 30-99% by weight of the polyamide, particularly preferably 40-98% by weight, particularly preferably 50-96% by weight and 1-70% by weight of the polyether ester amide and / or the polyether amide. Mixtures from 2-60% by weight and particularly preferably 4-50% by weight are used. Here, the polyether amide is advantageous.

In addition to the polyamide, the molding material can contain other components such as impact resistant improvers, other thermoplastic resins, plasticizers and other conventional additives. All that is required is for the polyamide to form a matrix of molding material. Suitable impact improvers are, for example, ethylene / α-olefin-copolymers advantageously selected from: a) Ethylene 20-96, preferably ethylene / C with 25-85% by weight₃-C₁₂-Α-olefin-copolymer. C₃-C₁₂As the -α-olefin, for example, propene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene or 1-dodecene are used. Typical for this are ethylene-propylene-rubber and LLDPE and VLDPE. b) Ethylene 20-96, preferably 25-85% by weight and unconjugated diene, such as bicyclo (2.2.1) heptadiene, hexadiene-1,4, dicyclopentadiene or 5-ethylidenenorbornene up to about 10% by weight Ethylene / C₃-C₁₂-Α-olefin / non-conjugated dienter polymer. C₃-C₁₂Similarly, as the -α-olefin, for example, propene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene or 1-dodecene are suitable.

For example, the production of the copolymer or terpolymer using a Ziegler-Natta catalyst is a prior art.

Other suitable impact modifiers are styrene-ethylene / butylene-block copolymers. Advantageously, styrene-ethylene / butadiene-styrene-block copolymers (SEBS), which can be obtained by hydrogenation of styrene-butadiene-styrene-block copolymers, are used. However, a two-block system (SEB) or a multi-block system can also be used. This type of block copolymer is a prior art.

The impact-resistant improver advantageously comprises a main chain polymer and an unsaturated dicarboxylic acid anhydride, unsaturated dicarboxylic acid or unsaturated dicarboxylic acid mono in a known manner at a concentration sufficient for good bonding to the polyamide. It contains an acid anhydride group resulting from a thermal or radical reaction with an alkyl ester. Suitable reagents are, for example, maleic acid, maleic anhydride, maleic acid monobutyl ester, fumaric acid, citraconic anhydride, aconitic acid or itaconic anhydride. In this way, preferably 0.1-4% by weight of unsaturated anhydride is grafted onto the impact-resistant improver. According to prior art, unsaturated anhydrous dicarboxylic acids or precursors thereof may be grafted with other unsaturated monomers such as styrene, α-methylstyrene or inden.

Other suitable impact modifiers are the following monomer units: a) One or more α-olefins with 2 to 12 C atoms 20 to 94.5% by mass, b) Below: --Acrylic acid or methacrylic acid or its salt Acrylic acid or methacrylic acid and optionally a free hydroxyl-or epoxy functional group C₁-C₁₂-Ester with alcohol --Acrylonitrile or methacrylonitrile --Acrylamide or methacrylamide 1 or more acrylic compounds selected from 5-79.5% by mass, c) Olefinically unsaturated epoxide, carboxylic acid anhydride, carboxylic acid imide, oxazoline or oxadinone 0.5-50% by mass It is a copolymer containing.

The copolymer is composed of, for example, the following monomers, but the following enumeration is not exhaustive: a) α-olefins such as ethylene, propene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene or 1-dodecene; b) Acrylic acid, methacrylic acid, or a salt thereof, such as Na as a counterion.⁺Or Zn²⁺Salts with; methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, n-hexyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, dodecyl acrylate, methyl methacrylate, ethyl methacrylate , N-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, hydroxyethyl acrylate, 4-hydroxybutyl methacrylate, glycidyl acrylate, glycidyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide, N-methylacrylamide, N, N-dimethylacrylamide, N-ethylacrylamide, N-hydroxyethylacrylamide, N-propylacrylamide, N-butylacrylamide, N- (2-ethylhexyl) acrylamide, methacrylicamide, N-methylmethacrylate, N, N-dimethylmethacrylate Amid, N-ethylmethacrylate, N-hydroxyethylmethacrylate, N-propylmethacrylate, N-butylmethacrylate, N, N-dibutylmethacrylate, N- (2-ethylhexyl) methacrylate; c) Vinyloxylan, allyloxylane, glycidyl acrylate, glycidyl methacrylate, maleic anhydride, aconitic anhydride, itaconic anhydride, and dicarboxylic acids produced by the reaction of the anhydride with water; maleimide, N-methylmaleimide, N-ethylmaleinimide, N-butylmaleimide, N-phenylmaleinimide, aconitate imide, N-methylaconitate imide, N-phenylaconytic acidimide, itaconic acidimide, N-methylitaconateimide, N-phenyl Imide itaconate, N-acryloylcaprolactam, N-methacryloylcaprolactam, N-acryloyllaurinlactam, N-methacryloyllaurinlactam, vinyloxazoline, isopropenyloxazoline, allyloxazoline, vinyloxadinone or isopropenyloxadinone.

When glycidyl acrylate or glycidyl methacrylate is used, they also act as an acrylic compound b), so if the amount of glycidyl (meth) acrylate is sufficient, other acrylic compounds are included. No need. In the particular embodiment described above, the copolymer is a unit of the following monomers: a) One or more α-olefins with 2 to 12 C atoms 20 to 94.5% by mass, b) Below: --Acrylic acid or methacrylic acid or its salt --Acrylic acid or methacrylic acid and C₁-C₁₂-Ester with alcohol --Acrylonitrile or methacrylonitrile --Acrylamide or methacrylamide 1 or more acrylic compounds selected from 0 to 79.5% by mass c) Epoxy group-containing acrylic acid or methacrylic acid ester 0.5-80% by mass In that case, the sum of b) and c) is at least 5.5% by mass.

The copolymer may contain a small amount of the above-mentioned monomers such as maleic acid dimethyl ester, fumaric acid dibutyl ester, itaconic acid diethyl ester or styrene, as long as other polymerization-introduced monomers do not significantly impair the properties.

The production of this type of copolymer is prior art. Many of these various types are commercially available, such as LOTADER.^(R)It can be obtained under the name (Arkema; ethylene / acrylate / three components or ethylene / glycidyl methacrylate). In one advantageous embodiment, the molding material of the layer according to I. is in this case the following components: 1. Polyamide 60-96.5 parts by mass, 2. Impact resistant component containing an acid anhydride group 3 to 39.5 parts by mass, wherein the impact resistant component is selected from ethylene / α-olefin-polymer and styrene-ethylene / butylene-block copolymer. To be 3. Copolymer containing the following monomer units 0.5 to 20 parts by mass: a) One or more α-olefins with 2 to 12 C atoms 20 to 94.5% by mass, b) One or more acrylic compounds selected from the following 5-79.5% by mass: --Acrylic acid or methacrylic acid or its salt Acrylic acid or methacrylic acid and optionally a free hydroxyl-or epoxy functional group C₁-C₁₂-Ester with alcohol --Acrylonitrile or methacrylonitrile --Acrylamide or methacrylamide c) Olefinically unsaturated epoxide, carboxylic acid anhydride, carboxylic acid imide, oxazoline or oxadinone 0.5-50% by mass At that time, the sum of the mass parts of the components according to 1, 2 and 3 is 100.

In another advantageous embodiment, in this case the molding material comprises: 1. Polyamide 65-90 parts by mass, especially advantageously 70-85 parts by mass, 2. Impact resistance component 5 to 30 parts by mass, especially preferably 6 to 25 parts by mass, especially advantageously 7 to 20 parts by mass, 3. Copolymer containing the following monomer units in an advantageous manner 0.6 to 15 parts by mass, particularly advantageously 0.7 to 10 parts by mass: a) 1 or more α-olefins 30-80% by mass, b) 1 or more acrylic compounds 7 to 70% by mass, particularly advantageously 10 to 60% by mass, c) Olefin-based unsaturated epoxides, carboxylic acid anhydrides, carboxylic acid imides, oxazolines or oxadinones 1-40% by mass, particularly preferably 5-30% by mass.

Further, as the impact resistant component, nitrile rubber (NBR) containing a functional group or hydrogenated nitrile rubber (H-NBR) may be used as the case. The corresponding molding material is described in US2003 / 0220449A1.

Other thermoplastic resins that may be included in the layer molding material according to I. are, in the first place, polyolefins. In one embodiment, the polyolefin may contain an acid anhydride group, as described in detail above in the case of impact-resistant improvers, and in that case, together with a defunctionalized impact-resistant improver. May exist in. In another embodiment, the polyolefin is not functionalized and is present in the molding material in combination with a functionalized impact resistant improver or functionalized polyolefin. The concept of "functionalization" means that the polymer has a group capable of reacting with a polyamide terminal group, such as an acid anhydride group, a carboxyl group, an epoxy group or an oxazoline group, according to the prior art. Here, the following composition is advantageous: 1. Polyamide 50-95 parts by mass, 2. 1 to 49 parts by mass of functionalized or non-functionalized polyolefin, and 3. Functionalized or defunctionalized impact resistance improver 1-49 parts by mass, At that time, the sum of the mass parts of the components according to 1, 2, and 3 shall be 100.

The polyolefin is, for example, polyethylene or polypropylene. In principle, all commercially available types can be used. For example: high, medium or low density straight line polyethylene, LDPE, ethylene-acrylic ester-copolymer, ethylene-vinyl acetate-copolymer, isotactic or atactic homopolypropylene, propene and ethene and / or Random copolymer with butene-1, ethylene-propylene-block copolymer, etc. Polyolefins can be produced by all known methods, such as by Ziegler-Natta, by the Philips method, by metallocene, or by radicals. The polyamide may be, for example, PA6 and / or PA66 in this case.

In one possible embodiment, the molding material contains 1-25% by weight of the plasticizer, particularly preferably 2 to 20% by weight, particularly preferably 3 to 15% by weight.

Its use in plasticizers and polyamides is known. An overview of suitable plasticizers for polyamides can be quoted from Gaechter / Mueller, Kunststoffadditive, C. Hanser Verlag, 2nd Edition, p. 296.

Conventional compounds suitable as plasticizers are, for example, esters of p-hydroxybenzoic acid having 2 to 20 C atoms in the alcohol component, or aryl sulfonic acids having 2 to 12 C atoms in the amine component. Amides, preferably benzenesulfonic acid amides. Plasticizers include p-hydroxybenzoic acid ethyl ester, p-hydroxybenzoic acid octyl ester, p-hydroxybenzoic acid-i-hexadecyl ester, toluenesulfonic acid-n-octylamide, benzenesulfonic acid-n-butylamide or benzene. The sulfonic acid-2-ethylhexylamide is applicable.

In addition, the molding material can still contain the usual amounts of additives required for the adjustment of predetermined properties. Examples of this include pigments or fillers such as carbon black, titanium dioxide, zinc sulfide, silicates or carbonates, reinforcing fibers such as glass fiber, processing aids such as wax, zinc stearate or calcium stearate, flame retardants, etc. For example magnesium hydroxide, aluminum hydroxide or melamine cyanurate, antioxidants, UV stabilizers, and additives that impart antistatic properties or conductivity to the product, such as carbon fiber, graphite fiber, stainless steel or conductive carbon. It is a fiber made of black. The good mechanical resistance of the polyamide coating is particularly advantageous, especially when the viscosity of the polyamide molding material applied is 240 ° C, shear rate 0.1 1 / s, at least 2000 Pa · s, preferably at least 2300 Pa · s. It is obtained when it is at least 3000 Pa · s, particularly advantageously at least 5000 Pa · s, and extremely particularly advantageously at least 8000 Pa · s. The viscosity was measured with a cone plate viscometer according to ASTM D 4440-3.

The high viscosity of the polyamide molding material is usually associated with the high molecular weight of the polyamide. One measure of the molecular weight of polyamide is solution viscosity. Within the scope of the present invention, the relative solution viscosity η of the polyamide in the applied molding material, measured by ISO 307 at 23 ° C in a 0.5 mass% solution in m-cresol._relIt is advantageous that is at least 1.8, particularly favorably at least 2.0, particularly favorably at least 2.1, and extremely particularly favorably at least 2.2.

A known method for producing such a polyamide is post-solid phase condensation from granulated low viscosity polyamide to high viscosity polyamide at a temperature lower than the melting temperature. The method is described, for example, in CH359286 and US3821171. Usually, the post-solid phase condensation of the polyamide is carried out in a batch or continuous operation dryer under an inert gas or vacuum. By the above method, extremely high molecular weight polyamide can be produced.

Another method of producing high viscosity polyamides is continuous postcondensation in the melt using various modes of screwing equipment. WO2006 / 079890 teaches that high viscosity polyamide molding materials can be obtained by mixing high molecular weight polyamides and low molecular weight polyamides.

In addition, the achievement of high viscosity polyamides or polyamide molding materials is possible by the use of augmented additives; suitable additives or methods are described, for example, in the following literature: WO98 / 47940, WO96 / 34909, WO01 / 66633, WO03 / 066704, JP-A-01 / 197526, JP-A-01 / 236238, DE-B-2458733, EP-A-1329481, EP-A-1518901, EP-A1512710, EP-A-1690889, EP-A-1690890 and WO 00/66650.

However, the molding material produced by the prior art usually requires extremely high power consumption or extremely high rotational moment during extrusion, and the pressure at the nozzle is extremely high. In addition, high shear forces result in perceptible chain decomposition, which leads to a reduction in molecular weight during processing.

For the above reasons, within the scope of the present invention, it is advantageous to condense the polyamide molding material with a molecular weight-enhancing additive for the first time during the processing step. Therefore, the use of tubes as required is also the subject of the present invention, in which the extruded layer from the polyamide molding material is subjected to the following method step: a) Process of preparing polyamide molding material; b) The step of making a premixture of the polyamide molding material with an additive additive, eg, a compound having at least 2 carbonate units; c) The steps of optionally storing and / or transporting the mixture, and d) Next, the mixture is extruded, and at that time, condensation is carried out for the first time in this step. It was given by.

In the case of the addition mode, it was found that during processing, at the same time, with a small motor load, a significant increase in melt stiffness occurs. Therefore, it is possible to achieve a high processing amount in spite of the high melt viscosity during processing, which brings about an improvement in the economic efficiency of the manufacturing method. The method is exemplified below when the additive is a compound having at least 2 carbonate units.

Advantageously, the starting compound has a molecular weight of more than 5000, especially more than 8000 M_nHave. In this case, a polyamide in which the terminal group is present at least partially as an amino group is used. For example, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80% or at least 90% of the terminal groups are present as amino terminal groups. The production of polyamides with a relatively high amino-terminal group content using diamines or polyamines as modifiers is a prior art. In this case, an aliphatic, alicyclic or aromatic aliphatic diamine having 4 to 44 C atoms is advantageously used as a regulator in the production of the polyamide. Suitable diamines are, for example, hexamethylenediamine, decamethylenediamine, 2,2,4- to 2,4,4-trimethylhexamethylenediamine, dodecamethylenediamine, 1,4-diaminocyclohexane, 1,4- or 1, 3-Dimethylaminocyclohexane, 4,4'-diaminodicyclohexylmethane, 4,4'-diamino-3,3'-dimethyldicyclohexylmethane, 4,4'-diaminodicyclohexylpropane, isophoronediamine, m-xylylenediamine or paraxylylene It is a range amine.

In another advantageous embodiment, polyamines are used as regulators and at the same time as branching agents in the production of polyamides. Examples of this are diethylenetriamine, 1,5-diamino-3- (β-aminoethyl) pentane, tris (2-aminoethyl) amine, N, N-bis (2-aminoethyl) -N', N'bis [ 2- [Bis (2-aminoethyl) amino] -ethyl] 1,2-ethanediamine, dendrimer and polyethyleneimine, especially branched polyethyleneimine, which polyethyleneimine can be obtained by polymerization of aziridine (Houben). -Weyl, Methoden der Organischen Chemie, E20, pp. 1482-1487, Georg Thieme Verlag Stuttgart, 1987), and usually has the following amino group distribution: Primary amino group 25-46%, Secondary amino group 30-45%, and Tertiary amino group 16-40%.

Compounds with at least 2 carbonate units are used in an amount ratio of 0.005-10% by weight, calculated as a ratio to the polyamide used. Advantageously, the ratio is in the range of 0.01 to 5.0% by mass, and particularly preferably in the range of 0.05 to 3% by mass. The concept of "carbonate" here means an ester of a carbon acid and especially a phenol or alcohol.

The compound having at least 2 carbonate units may be a small molecule, an oligomer or a polymer. The compound may consist entirely of carbonate units or may have other units. The unit is preferably an oligo-or polyamide-,-ester-,-ether-,-ether-esteramide-or-etheramide unit. Such compounds can be produced by known oligomerization or polymerization methods or by polymerization-like reactions.

In one advantageous embodiment, the compound having at least 2 carbonate units is, for example, a polycarbonate based on bisphenol A or a block copolymer comprising a polycarbonate block of this type.

By introducing a compound having at least 2 carbonate units used as an additive in a masterbatch form, a more accurate supply of the additive can be achieved. That is because a relatively large amount is used. In addition, it has been found that improved extrusion quality is achieved by using a masterbatch. The master batch contains, as a matrix material, a polyamide that is also condensed in the method according to the invention or a polyamide that is compatible with it, but incompatible polyamides are also partially to the polyamide that should be condensed under reaction conditions. It binds to, which results in compatibility. Polyamides used as matrix materials in masterbatches have a molecular weight of more than 5,000, especially more than 8,000._nHave. In this case, a polyamide having a terminal group mainly as a carboxylic acid group is advantageous. For example, at least 80%, at least 90% or at least 95% of the terminal groups are present as acid groups.

The concentration of the compound having at least 2 carbonate units in the masterbatch is preferably 0.15 to 50% by weight, particularly preferably 0.2 to 25% by weight, particularly preferably 0.3 to 15% by weight. The production of such a masterbatch is carried out by a conventional method known to those skilled in the art.

Suitable compounds with at least 2 carbonate units as well as suitable masterbatch are described in detail in WO 00/66650 and are explicitly cited herein.

The present invention is applicable to polyamides that are production-constrained and contain at least 5 ppm phosphorus in the form of acidic compounds. In this case, 0.001 to 10% by mass of a weak acid salt is added to the polyamide molding material before or during compounding. Suitable salts are disclosed in DE-A10337707, which is explicitly cited.

However, the present invention is similarly applicable to polyamides containing or not containing less than 5 ppm of phosphorus in the form of acidic compounds due to production restrictions. In this case, a corresponding salt of a weak acid can be added, but it is not always necessary.

Compounds with at least 2 carbonate units are added either as is or as a masterbatch advantageously after compounding, i.e. after the production of the polyamide molding material, but at the latest during processing. .. Advantageously, during processing, the polyamide to be condensed or the polyamide molding material to be condensed is mixed as granules with granules or powders of compounds having at least 2 carbonate units or a corresponding masterbatch. However, it is also possible to produce a granular mixture of the compounded finished polyamide molding material with a compound or masterbatch having at least 2 carbonate units, which can be subsequently transported or stored and then processed. Of course, the powder mixture is also done accordingly. It is important that the mixture is melted for the first time during processing. It is desirable to thoroughly mix the melt during processing. However, it is also good to feed the masterbatch as a melt stream into the melt of the polyamide molding material to be processed using the provided extruder and then mix thoroughly.

Instead of compounds having at least 2 carbonate units, it is also possible to use, for example, all other suitable additive additives disclosed in the above literature. Again, the preferred amount ratio is 0.005 to 10% by weight, preferably 0.01 to 5.0% by weight, particularly preferably 0.05 to 3% by weight, calculated as a ratio to the polyamide used.

The applied polyamide layer must be at least thick enough that the polyamide layer can form as a cohesive layer under the applied conditions. Advantageously, the layer thickness is at least 1.0 mm, particularly preferably at least 1.2 mm, particularly preferably at least 1.4 mm.

The polyamide layer may be applied directly onto the metal surface. However, in general, there is at least one other layer between the metal surface and the polyamide layer. The layer may be, for example, the following layers: --For example, the ceramic layer by WO03 / 093374; --For example, a base layer from an epoxy resin (US5580659) or an aqueous mixture of an epoxy resin and a polyacrylate latex (WO00 / 04106); --A layer from polyolefin with functional groups. Examples of the functional group include a carboxyl group or an acid anhydride group (WO02 / 094922), an epoxy group or an alkoxysilane group (EP-A-0346101). The polyolefin layer may be foamed. Polyolefins are advantageously polyethylene or polypropylene; --Other constituent adhesion promoters that should be guaranteed not to interfere with the bond between the polyamide layer and the underlying material under mechanical stress; -Textile reinforcements in the form of fabrics or mats, for example from fiberglass or aramid fibers (Kevlar).

The advantageous layering is as follows: Metal / ceramic layer / polyamide layer; Metal / ceramic layer / base layer / polyamide layer; Metal / Ceramic layer / Underlayer / Adhesion accelerator layer / Polyamide layer; Metal / Underlayer / Polyamide layer; Metal / Underlayer / Adhesion Accelerator Layer / Polyamide Layer; Metal / base layer / polyolefin layer / polyamide layer.

In each of the above cases, the polyamide layer can be followed outward by at least one other layer, such as a foam jacket for insulation.

The optional ceramic layer, base layer and / or polyolefin layer is applied to the tubing by any of the methods. A preferred method is prior art.

The polyamide layer is applied, for example, by tube extrusion or screw extrusion, as is also the prior art for polyolefin layers. In a possible variant, the polyamide layer can also be made and applied by simultaneous extrusion of the multilayer composite with the polyolefin layer to be applied.

The outer diameter of the metal tube is advantageously at least 25 mm and up to 4800 mm, especially advantageously at least 32 mm and up to 2500-1500 mm.

The individual members of the pipe are connected to the conduit as specified.

The conduit can be a transport conduit, a distribution conduit or a lifeline and can be implemented as a pressure tube or a non-pressure conduit. The conduits are, for example, remote heating heat, fresh water, wastewater, gas, air, oil, such as crude oil, light oil or heavy oil, fuels such as kerosene or diesel, petrochemicals, salt water, alkaline solutions, polishing materials, rubble or press. It may be used for transporting materials or dust and may be, for example, a supply pipe or a treatment pipe.

The conduit is laid uncut and / or without sand layers by known methods. Examples of this are the horizontal boring method, the old conduit crushing method (Berstlining), the plow work, the milling method and the microtunnel method.

The horizontal boring method ("Horizontal Directional Drilling"; HDD method) is one of the non-cutting conduit laying methods. First, a controlled pilot drilling is drilled in the section to be drilled. Subsequently, the drilling is expanded in one or more work paths. After that, the pipeline to be drawn is drawn from the end point stand to the drilling path. The HDD method is used, for example, when crossing rivers, defensive areas, alluvial plains in coastal areas, or crossing mountains. With the conventional technology, it is possible to drill holes up to 3000 m at present. The method is described, for example, in the DVGW Regulations by Working Sheet GW321.

The old conduit crushing method is one of the non-cutting pipe rehabilitation methods using the old pipeline. In this case, the old conduit will be destroyed and the new conduit will be drawn into the existing planned line. After pushing the rod into the old pipe, use a crushing head or roller cutting blade to break the old conduit. An extension placed behind it extends the feature line to the desired diameter. In this case, the original pipe diameter can be increased. The new tube is retracted at the same time as the crush-and the dilator. The old conduit crushing method is described in the manual RSV8 of the Pipe Rehabilitation Association.

In the case of plow work, a plow with a blade is used to drill a laying slit in the ground. Soil is pushed apart by the discharge element. The pipe is introduced into the slit in the same work process. The conduit will continue to be closed again quickly. In the case of the above method, the laying depth is limited to about 2 meters.

In the case of milling, a narrow tube groove is excavated by special equipment, and a tube is introduced into this tube groove in a similar work process. Soil waste is used as a filler. The milling cutter can be used up to a laying depth of about 2 meters. A DVGW working sheet (GW324) is currently under development for plow work and milling.

The microtunnel method is one of the remote control methods for propelling pipes. It starts from the shaft at the starting point (press-in shaft) and propels the groove using propulsion equipment with a press-fit part and a drilling head. It is interpreted as something to do. In this case, the soil is removed by the hydraulic drilling head. To reduce friction and to support the soil in a short period of time against collapse, the drilling head has a support (bentonite solution for loose non-viscous soil; for viscous or rocky soil). Water is sufficient) is sprayed. Waste stone is transported to and upwardly (over several days) through the press-fitting groove through a screw conveyor and-tube extending into the already press-fitted pipe. Here, the soil and the support agent are separated. Support agents will continue to be reused.

Other points are IRB-Literaturdokumentation 3366, "Grabenlose Rohrverlegung" (Herausgeber: Fraunhofer-Informationszentrum Raum und Bau IRB, Stuttgart), ISBN 978-38167-3291-4, Fraunhofer IRB Verlag.

Based on the high mechanical strength, good wear properties, extremely high scratch resistance and optimum thickness of the applied polyamide layer, according to the present invention, it has good corrosion resistance, as well as non-cutting and no sand layer. The resistance of the jacket required for the laying technique can also be guaranteed.