Clad pipeline

Translation of description of equivalent WO 2009027429 A2

Coated pipe

The invention relates to the use of a metallic conduit, whose surface is coated with a polyamide layer, for preparing a trenchless or sand beds freely laid pipeline, and the pipeline produced in this way.

Dispensing, disposal or product lines of metal are currently, for example, a polyolefin such as polyethylene or polypropylene sheathed (WO 2002/094922; US 2002/0066491; EP-A-0346101).. The coatings or wrappings are used primarily to prevent corrosion; They are described by appropriate standards. For the

Polyolefin coatings are the example, the DIN EN 10288 or DIN 30678th In the case of Polyolefinumhüllung this layer is produced for example by means of hose or wrapping extrusion. To promote adhesion, epoxy and adhesive layers may be applied one after the other prior to extrusion.

Another prior art defined by the DIN EN 10310 (German version EN 10310: 2003) is regulated, provides for the coating of steel pipes before for onshore and offshore pipelines using polyamide powder. The polyamide coating is applied by dipping in a Fluidadbett, spraying or roll coating. Due process can be applied using powder coating only relatively thin layers on the metal, which are unsuitable for a grave loose laying of pipelines. A particular disadvantage is that, for the coating a powder of a relatively low molecular weight polyamide must be used to ensure a good flow of the melt on the hot metal surface. but a thus-obtained coating has an insufficient mechanical strength; it is primarily used to prevent corrosion. A particular disadvantage is also, that it is not possible in this manner to apply a polyamide layer on a tube which already contains a coating of a polyolefin or an adhesive layer.

Moreover, thermoset coatings on epoxy or polyurethane are known; they serve only to prevent corrosion and provide no protection against mechanical damage is. In sand bedded free installation or at a grave loosely laid, for example by means Pflüg-, drilling or pressing method, but the pressure applied by the prior art corrosion protection is not sufficiently mechanically robust. By pushing or frictional stress while laying the polymer layer is in places so damaged that the metal comes into contact with water. Then through the onset of corrosion, the service life of the pipe is considerably reduced. The same applies for. Example, when mechanical stresses caused by the inadvertent hitting an excavator bucket during repair work in the later operation. Pipelines with such anticorrosion coatings must be embedded in stone-free material. In the prior art thus coated or coated pipelines are often protected by an additionally applied cement mortar shell from mechanical damage.

The application of the cement mortar layer is done in a separate operation. After applying the mortar layer must cure for at least five days before the tubes can be further handled. This step is therefore very time-consuming and therefore costly. Prior art mortar shell found for example in the following publications: US 5,580,659, DE 42 08 047 Cl, DE 42 01 113 Cl, DE 33 05 158 Al, US 4,454,172 and US 4361 336. National are the requirements the cement mortar shell in DVGW GW regulated 340th However, such mortar layers increase the weight of the pipes considerably; thus handling becomes difficult. The weight-based charge capacity of the transport vehicles decreases.

The object of the invention is therefore to provide a coated metal pipe available, which retains even without additional protective measures under mechanical stress, eg. As in a grave loose or sand bed-free installation, the integrity of the coating, so that the metal tube effective against corrosion is protected. In addition, a firm adhesion to the pipe or to it, possibly existing coatings to be achieved. Overall, a tube is to be provided, which is easy to handle and inexpensive to produce.

These and other of the application documents visible objects are achieved by the use of a metallic conduit for producing an underground trenchless and / or sand beds freely laid pipeline, the pipe with an extruded Layer is wrapped from a polyamide molding composition.

The Betriff "underground" also includes the laying in the bottom of a water body, eg. As in the seabed, with.

The tube consists for example of steel, stainless steel, copper, aluminum, cast iron, galvanized steel, metal alloys such. B. GALFAN coated steel or any other metal. The tube may be prepared by all methods of the prior art.

The polyamide is produced from a combination of diamine and dicarboxylic acid from a CO- amino carboxylic acid or the corresponding lactam. Basically, any polyamide can be used, for example PA46, PA6, PA66 or copolyamides on this basis with units derived from terephthalic acid and / or isophthalic acid (commonly referred to as PPA refers). In a preferred embodiment, the monomer units contain an average of at least 8, at least 9 or at least 10 C-atoms. For mixtures of lactams here the arithmetic mean is considered. In a combination of diamine and dicarboxylic acid, the arithmetic mean of the carbon atoms of diamine and dicarboxylic acid in this preferred embodiment, at least 8 must be at least 9 or at least 10th Suitable polyamides are for example: PA610 (prepared from hexamethylenediamine [6 carbon atoms] and sebacic acid [10 carbon atoms], the average number of carbon atoms in the monomer units is here thus 8), PA88 (prepared from octamethylenediamine and 1.8-octanedioic acid) , PA8 (producible from capryllactam), PA612, PA810, PA108, PO9, PA613, PA614, PA812, PA128, Palolo, Palo, PA814, PA148, PA1012, PAI l, PA1014, PA1212 and PA12. The preparation of polyamides is known in the art. Of course, can be used copolyamides based thereon, optionally, monomers such as caprolactam can be used.

The polyamide may also be a polyether ester amide or a polyetheramide. Polyether amides are, in principle, for. Example, from DE-OS 30 06 961.. They contain as comonomer ether diamine a polyethylene. Suitable polyether diols are through conversion of the corresponding polyether by reductive amination or coupling to acrylonitrile with subsequent hydrogenation accessible (for example, EP-AO 434 244;. EP-AO 296 852). They generally have a number average molecular weight 230-4000; their polyetheramide is preferably from 5 to 50 wt .-%.

Commercially AVAILABLE polyether starting from propylene glycol are as JEFFAMIN^® D types commercially available from the Fa. Huntsman. Basically, polyether are starting from 1.4-butanediol or 1,3-butanediol, or mixed polyether built up, for example with random or blockwise distribution of originating from the diol units, well suited.

Mixtures of various polyamides, sufficient compatibility can also be provided, used. Acceptable polyamide combinations are known in the art; For example, the combination PA12 / PA1012, PA12 / PA1212, PA612 / PA12, PA613 / PA12, PA1014 / PA12 and PA610 / PA12 are listed. If in doubt, compatible combinations can be determined by routine tests.

In a preferred embodiment, a mixture of 30 to 99 wt .-%, particularly preferably 40 to 98 wt .-% and especially preferably 50-96 wt .-% of polyamide in the narrow sense as well as 1 to 70 wt .-%, particularly preferably 2 to 60 wt .-% and especially preferably 4 to 50 wt .-% polyetheresteramide and / or polyether amide used. Polyether amides are preferred here.

In addition to polyamide molding composition can comprise further components such. As impact modifiers, other thermoplastics, plasticizers, and other conventional additives. The only requirement is that the polyamide forms the matrix of the molding composition.

Suitable impact modifiers are ethylene / α-olefin copolymers, preferably selected from a) ethylene / C₃- To C₂-α-olefin copolymers having 20 to 96, preferably 25 to 85 wt .-% ethylene. As C3-Ci₂-OC-01efin for example, propene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene or 1-dodecene is used. Typical examples are ethylene

Propylene rubber and LLDPE and VLDPE. b) ethylene / C₃- To C₂-α-olefin / unconjugated diene terpolymer with 20 to 96, preferably 25 to 85 wt .-% of ethylene and up to a maximum of about 10 wt .-% of an unconjugated diene, such as bicyclo (2.2.1) heptadiene, 1,4-hexadiene, dicyclopentadiene or 5-ethylidene norbornene. As C₃- To C₂-CC-OIeFm for example, propene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene or 1-dodecene are also suitable.

The preparation of these copolymers or terpolymers, for example with the aid of a Ziegler-Natta catalyst, is prior art.

Other suitable impact modifiers include styrene-ethylene / butylene block copolymers. In this case, preferably, styrene-ethylene / butylene-styrene block copolymers (SEBS) are used which are obtainable by hydrogenating styrene-butadiene-styrene block copolymers. It is also possible to use diblock systems (SEB) or multiblock systems are used. Such block copolymers are known in the art.

These impact modifiers preferably contain anhydride groups, which are introduced in a known manner by thermal or free-radical reaction of the backbone polymer with an unsaturated dicarboxylic acid, an unsaturated dicarboxylic acid or an unsaturated dicarboxylic acid in a concentration sufficient for good bonding to the polyamide. Suitable reagents are, for example, maleic anhydride, maleate, fumaric acid, citraconic anhydride, aconitic or itaconic. In this manner, are preferably grafted onto the impact modifier 0.1 to 4 wt .-% of an unsaturated anhydride. According to the prior art, the unsaturated dicarboxylic anhydride or its precursor can also be grafted together with another unsaturated monomer such as styrene, methylstyrene or indene CC.

Other suitable impact modifiers are copolymers containing units of the following monomers: a) from 20 to 94.5 wt .-% of one or more α-Olefϊne having 2 to 12 carbon atoms, b) 5 to 79.5 wt .-% of a or more acrylic compounds selected from

- Acrylic or methacrylic acid or salts thereof,

- Esters of acrylic or methacrylic acid with a Cl to C12 alcohol, which may optionally bear a free hydroxy or epoxy,

- Acrylonitrile or methacrylonitrile,

- Acrylamides or methacrylamides, c) from 0.5 to 50 wt .-% of an olefinically unsaturated epoxide, carboxylic anhydride, carboximide, oxazoline or oxazinone.

This copolymer is composed, for example, from the following monomers, this enumeration is not exhaustive: a) α-olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene or 1-dodecene ; b) acrylic acid, methacrylic acid or their salts, for example with Na^® or Zn^2Θ as a counter ion; 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, hydroxy ethyl acrylate, 4-hydroxybutyl methacrylate,

Glycidyl acrylate, glycidyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide, N-methyl acrylamide, N, N-dimethylacrylamide, N-ethylacrylamide, N-hydroxyethylacrylamide, N-propylacrylamide, N-butylacrylamide, N- (2-ethylhexyl) acrylamide, methacrylamide, N - methylmethacrylamide, N, N-dimethylmethacrylamide, N-ethylmethacrylamide, N-hydroxyethylmethacrylamide, N-propylmethacrylamide, N-butylmethacrylamide, N₅N-

Dibutylmethacrylamid, N- (2-ethylhexyl) methacrylamide; c) vinyloxirane Allyloxiran, glycidyl acrylate, glycidyl, anhydride, aconitic, itaconic, also arising from these anhydrides by reaction with water dicarboxylic acids; Maleimide, N-methyl maleimide, N-ethylmaleimide, N-butylmaleimide, N-phenyl, Aconitsäureimid, N-

Methylaconitsäureimid, N-Phenylaconitsäureimid, Itaconsäureimid, N-Methylitacon- acid imide, N-Phenylitaconsäureimid, N-acryloylcaprolactam, N-Methacryloylcaprolactam, N-Acryloyllaurinlactam, N-Methacryloyllaurinlactam, vinyl oxazoline, isopropenyl oxazoline, Allyloxazolin, Vinyloxazinon or Isopropenyloxazinon.

In one use of glycidyl acrylate or glycidyl these act simultaneously as acrylic compound b), so that when a sufficient amount of the glycidyl (meth) acrylate to be contained no further acrylic compound need. In this particular embodiment, the copolymer contains units of the following monomers:

a) from 20 to 94.5 wt .-% of one or more α-olefins having 2 to 12 carbon atoms, b) 0 to 79.5 wt .-% of one or more acrylic compounds, selected from

- Acrylic or methacrylic acid or salts thereof,

- Esters of acrylic or methacrylic acid with a Ci to Ci₂-Alcohol,

- Acrylonitrile or methacrylonitrile,

- Acrylamides or methacrylamides, c) from 0.5 to 80 wt .-% of an ester of acrylic acid or methacrylic acid, the a

contains epoxy group, the sum of b) and c) at least 5.5 wt .-% results.

The copolymer may contain a small amount of other copolymerized monomers, provided these do not affect the properties significantly, such as

Maleate, fumarate, diethyl itaconate or styrene.

The preparation of such copolymers is known in the art. A variety of different types of these is obtainable as a commercial product, for example LOTADER® (Arkema; ​​ethylene / acrylate / third component or ethylene / glycidyl). In a preferred embodiment, the molding composition of the layer contains according to this I. the following components:

1. contains from 60 to 96.5 parts by weight of the polyamide, 2. 3 to 39.5 parts by weight of an impact, the acid anhydride groups, wherein said impact modifier is selected from ethylene / α-olefin copolymers and styrene-ethylene / butylene block copolymer, 3. 0.5 to 20 parts by weight of a copolymer comprising units of the following monomers: a) from 20 to 94.5 wt .-% of one or more α-olefins having 2 to 12 carbon atoms, b) 5 to 79.5 wt .-% of one or more acrylic compounds, selected from

Acrylic or methacrylic acid or salts thereof, Esters of acrylic or methacrylic acid with a Ci to Ci2 alcohol, which may optionally bear a free hydroxy or epoxy, acrylonitrile or methacrylonitrile, acrylamides or methacrylamides, c) 0.5 to 50 wt .-% of an olefinically unsaturated epoxide, carboxylic anhydride,

Carboximide, oxazoline or oxazinone,

wherein the sum of the parts by weight of the components is according to 1., 2. and 3. 100th

In a further preferred embodiment, the molding composition contains this:

1. 65 to 90 parts by weight and particularly preferably 70 to 85 parts by weight of the polyamide,

2. 5 to 30 parts by weight, particularly preferably 6 to 25 parts by weight, and particularly preferably 7 to 20 parts by weight of impact modifier,

3. 0.6 to 15 parts by weight and particularly preferably 0.7 to 10 parts by weight of the copolymer, which preferably contains units of the following monomers: a) from 30 to 80 wt .-% α-olefin (s), b) 7 to 70 wt .-% and particularly preferably 10 to 60 wt .-% of the acrylic compound (s), c) 1 to 40 wt .-% and particularly preferably 5 to 30 wt .-% of the olefinically unsaturated epoxide, carboxylic anhydride, carboximide, oxazoline or

Oxazinone.

Other impact and nitrile rubber (NBR) or hydrogenated nitrile rubber can be (H-NBR), which may optionally contain functional groups, also uses. Corresponding molding compositions are described in US2003 / 0220449A1.

Other thermoplastics that may be included in accordance with I. in the molding composition of the layer, are primarily polyolefins. They can, in one embodiment, as described above for the impact modifiers that contain anhydride groups, and then optionally present together with an unfunctionalized impact modifier. In another

Embodiment they are not functionalized and are in the molding composition in combination with a functionalized impact modifier or a functionalized Polyolefϊn ago. Of the Term "functionalized" means that the polymers are provided in accordance with the prior art with groups which can react with the polyamide end groups, for example, acid anhydride groups, carboxyl groups, epoxy groups or oxazoline groups Here the following compositions are preferred..:

1. 50 to 95 parts by weight of the polyamide,

2. 1 to 49 parts by weight of functionalized or unfunctionalized polyolefin and

3. 1 to 49 parts by weight of functionalized or unfunctionalized impact modifier, wherein the total parts by weight of the components according to 1., 2. and 3. 100.

The polyolefin is, for example, polyethylene or polypropylene. In principle, any commercially available type can be used. For example, are: Linear polyethylene of high, medium or low density, LDPE, ethylene-acrylic ester copolymers, ethylene-vinyl acetate copolymers, isotactic or atactic homopolypropylene, random copolymers of propylene with ethylene and / or butene-1, ethylene propylene block copolymers and the like. The polyolefin may be prepared by any known methods, for example Ziegler-Natta, Phillips according to the method by metallocenes or free-radically. The polyamide may be in this case, for example, PA6 and / or PA66.

In one possible embodiment, the molding composition comprises 1 to 25 wt .-% plasticizer, particularly preferably 2 to 20 wt .-% and especially preferably 3 to 15 wt .-%.

Plasticizers and their use in polyamides are known. A general overview of plasticizers suitable for polyamides, Gächter / Müller, Plastics Additives, C. Hanser Verlag, 2nd edition, p 296 can be removed.

Suitable as plasticizers, conventional compounds such. As esters of p-hydroxybenzoic acid with 2 to 20 C atoms in the alcohol component or amides of arylsulfonic acids having 2 to 12 carbon atoms in the amine component, preferably amides of benzenesulfonic acid.

Plasticizers are inter alia p-hydroxybenzoate, p-hydroxybenzoic octyl p-hydroxybenzoate, i-hexadecyl, toluenesulfonic n-octylamide, benzene sulfonic acid-n-butyl amide or benzene-2-ethylhexylamide questioned.

In addition, the molding composition can include customary amounts of additives required for adjusting certain properties. Examples include pigments or fillers such as carbon black, titanium dioxide, zinc sulfide, silicates or carbonates, reinforcing fibers such as glass fibers, processing aids such as waxes, zinc stearate or calcium stearate, flame retardants such as magnesium hydroxide, aluminum hydroxide or melamine cyanurate, antioxidants, UV stabilizers, and additives to the product antistatic properties or electrical conductivity imparting such. as carbon fibers, graphite, stainless steel fibers or conductive.

A good mechanical strength of the polyamide coating is in particular obtained when the viscosity of the applied polyamide molding composition at 240 ⁰C and a shear rate of 0.1 l / s at least 2000 s paper, preferably at least 2300 pa- s, particularly preferably at least 3000 Pa-s, particularly preferably at least 5000 Pa-s and most preferably at least 8000 Pa-s. The viscosity is determined in a cone plate viscometer according to ASTM D 4440-3.

High viscosity of the polyamide molding composition is generally associated with a high molecular weight of the polyamide. A measure of the molecular weight of the polyamide is the solution viscosity. In the invention, it is preferred that the relative

Solution viscosity η_rei of the polyamide in the applied molding composition, measured in a 0.5 wt .-% solution in m-cresol at 23 ⁰C according to ISO 307, at least 1.8, more preferably at least 2.0, particularly preferably at least 2.1 and most preferably at least 2.2.

A known method for preparing such polyamides is the solid-phase postcondensation of the granulated low-viscosity polyamides to high-viscosity polyamide at a temperature which is lower than the melting temperature. The method is described for example, in CH 359 286 and US 3,821,171. Normally, the solid-phase postcondensation of polyamides in a batch or continuous dryer is carried out under inert gas or vacuum. This method allows the preparation of polyamides having very high molecular weight. Another possibility for the production of high viscosity polyamides is the continuous after-condensation in the melt by using different types of screw apparatus. WO 2006/079890 indicates that high-viscosity polyamide molding compounds can be obtained by mixing a high molecular weight polyamide and a low molecular weight polyamide.

Moreover, access to high-viscosity polyamides or polyamide molding compositions by using constructive additives is possible; suitable additives or methods are described for example in the following publications: WO 98/47940, WO 96/34909, WO 01/66633, WO 03/066704, JP-A-01/197526, JP-A-01/236238, DE- B-24 58 733, EP-AI 329 481, EP-AI 518 901, EP-A-1512710, EP-AI 690 889, EP-AI 690 890 and WO 00/66650.

The molding compositions prepared according to this prior art, however, usually need during extrusion a very high power consumption and a very high torque and the pressure at the nozzle is very high. In addition occurs at the high shear forces in a discernible chain scission, leading to a reduction in molecular weight during processing.

For these reasons, it is preferable in the invention that the polyamide molding composition is first condensed during the processing operation with the aid of a molecular weight constituent additive. The invention therefore also provides the claimed use of a tube, wherein the extruded layer was applied from a polyamide molding composition by means of the following steps:

a) A polyamide molding composition was provided; b) a premix of the polyamide molding composition and of the constituent additive, for example a compound having at least two carbonate units was produced, c) the mixture was optionally stored and / or transported, and d) the mixture was subsequently used for extrusion, the first in this step, Condensation was carried out.

It has been found that in this manner of addition during the processing of a significant increase in melt stiffness occurs, combined with low engine load. Thus, Despite high melt viscosity, high throughputs are achieved during processing, resulting in an improvement in the economics of the production results. The method is described by way of example for the case where the constituent additive is a compound having at least two carbonate units.

Preferably have the starting compounds have molecular weights M_n of more than 5000, in particular greater than 8000. Polyamides are used, at least partially present their end groups as amino groups. For example, there are at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80% or at least 90% of the end groups as amino end groups. The preparation of polyamides with high amino end using diamines or polyamines as regulator is prior art. In the present case, in the preparation of the polyamide preferably an aliphatic, cycloaliphatic or araliphatic diamine having 4 to 44 carbon atoms used as regulators. Suitable diamines are, for example, hexamethylene diamine, decamethylene, 2,2,4- or 2,4,4-trimethylhexamethylenediamine, dodecamethylenediamine, 1.4-diaminocyclohexane, 1.4- or 1.3-dimethylamino cyclohexane, 4,4'-Diaminodicyclo- hexylmethan, 4.4 diamino-3.3 '-dimethyldicyclohexylmethan, 4.4 '-Diaminodicyclohexylpropan, isophorone diamine, metaxylylenediamine or paraxylylenediamine.

In a further preferred embodiment, a polyamine is used as a controller and at the same branching agents in the production of the polyamide. Examples are diethylenetriamine, 1,5-diamino-3- (beta-aminoethyl) pentane, tris (2-aminoethyl) amine, N, N-bis (2-aminoethyl) -N ', N' bis [2- [bis (2 aminoethyl) amino] ethyl] - 1, 2-ethanediamine, dendrimers, and also polyethyleneimines, in particular branched polyethyleneimines, which are obtainable by polymerization of aziridines (Houben-Weyl, Methods of organic Chemistry, volume E20, pages 1482-1487, Georg Thieme Verlag Stuttgart, 1987) and the following distribution of amino groups generally have:

25 to 46% of primary amino groups, 30-45% secondary amino groups and

16 to 40% tertiary amino groups. The compound having at least two carbonate units is used in a proportion of 0.005 to 10 wt .-%, calculated in relation to the polyamide used. Preferably this ratio is in the range of 0.01 to 5.0 wt .-%, particularly preferably in the range of 0.05 to 3 wt .-%. The term "carbonate" here means esters of carbonic acid in particular with phenols or with alcohols.

The compound having at least two carbonate units may be low molecular weight, oligomeric or polymeric. They may consist entirely of carbonate units or can have other units. These are preferably oligo- or polyamide, -ester, -ether-, -ether- esteramide or -etheramideinheiten. Such compounds can be prepared via known oligo- or polymerization processes or by polymer-analogous reactions.

In a preferred embodiment, the compound having at least two carbonate units is a polycarbonate, for example based on bisphenol A, or a block copolymer comprising a polycarbonate block.

The metered addition of the compound used as an additive with at least two carbonate units in the form of a masterbatch enables more accurate dosing of additive, since larger amounts are used. It also turned out that one achieves improved extrudate through the use of a masterbatch. The masterbatch comprises a matrix material preferably the polyamide, which is condensed in the inventive method, or a polyamide compatible therewith, but may also be incompatible polyamides out under the reaction conditions, a partial connection to the polyamide whose molecular weight, which causes compatibilization. The polyamide used as the matrix material in the masterbatch preferably has a molecular weight M_n of greater than 5,000 and especially greater than 8000. In this case, those polyamides, preferred are present whose end groups mainly as carboxylic acid groups. Example, at least 80%, at least 90% or at least 95% of the end groups as acid groups.

The concentration of the compound having at least two carbonate units in the masterbatch is preferably 0.15 to 50 wt .-%, particularly preferably 0.2 to 25 wt .-% and especially preferably from 0.3 to 15 wt .-%. The preparation of such a masterbatch in the usual manner known to the expert.

Suitable compounds having at least two carbonate units and suitable masterbatches in WO 00/66650, which are incorporated herein by reference, described in detail.

The invention is applicable to polyamides, of the preparation, at least 5 ppm of phosphorus in the form of an acidic compound. In this case, a salt of a weak acid, the polyamide molding composition prior to compounding or during compounding 0.001 to 10 wt .-%, based on the polyamide, is added. Suitable salts are disclosed in DE-A 103 37 707, which is incorporated herein by reference.

However, the invention is equally applicable in polyamides, of the preparation, less than 5 ppm of phosphorus or no phosphorus in the form of an acidic compound. In this case, although may, but need not, a corresponding salt of a weak acid may be added.

The compound having at least two carbonate units is used as such or as a master batch preferably only after the compounding process, i.e. after the preparation of the

Polyamide molding composition, but added the latest during processing. Preferably mixing in processing the polyamide whose molecular weight or the polyamide whose molecular weight molding compound granules with the granules or powder of the compound having at least two carbonate units or the corresponding masterbatch. It can also be a mixture of pellets of the finished compounded polyamide molding composition with the compound having at least two carbonate units or with the masterbatch are then transported or stored and processed afterwards. Accordingly, also be dealt with powder mixtures. It is crucial that the mixture is melted until processing. Thorough mixing of the melt during processing is recommended. The masterbatch can be just as good, however, as

Melt stream can be metered by means of an auxiliary extruder into the melt of the processed polyamide molding composition and then mixed thoroughly. Instead of the compound having at least two carbonate units, any other suitable construction additive are used, for example, one disclosed in the above literature. Suitable mixing ratios are also here 0.005 to 10 wt .-%, calculated in relation to the polyamide, preferably 0.01 to 5.0 wt .-%, particularly preferably 0.05 to 3 wt .-%.

The coated polyamide layer must be at least thick enough that they can be produced under the conditions of the application as a closed layer. the layer thickness is preferably at least 1.0 mm, particularly preferably at least 1.2 mm and most preferably at least 1.4 mm.

The polyamide layer can be applied directly on the metal surface. In general, but is between the metal surface and the polyamide layer at least one further layer. For example, it may be the following layers:

- A ceramic layer, for example, according to WO 03/093374;

- A primer layer, for example made of epoxy resin (US 5580659) or a water-based mixture of epoxy resin and polyacrylate (WO 00/04106);

- A layer of a polyolefin which carries functional groups. As functional groups, for example carboxyl groups or acid anhydride groups come (WO 02/094922),

Epoxy or alkoxysilane (EP-AO 346 101) in question. The polyolefin layer may also be foamed. The polyolefin is preferably polyethylene or polypropylene;

- A different composite bonding agent which is to ensure that under mechanical stress of the composite polyamide layer and the base material is not impaired;

- A textile reinforcement in the form of cloth or mat, for example of glass fibers or aramid fibers (Kevlar).

Preferred layer arrangements are as follows: metal / ceramic layer / polyamide layer;

Metal / ceramic layer / primer layer / polyamide layer;

Metal / ceramic layer / primer layer / tie / polyamide layer; Metal / primer layer / polyamide layer;

Metal / primer layer / tie / polyamide layer;

Metal / primer layer / Polyolefmschicht / polyamide layer.

In each case, at least one further layer may outwards to the polyamide layer to connect, for example, a foam sheathing for thermal insulation.

A possible ceramic layer, primer layer and / or Polyolefmschicht is applied to the tube by any method. Suitable methods are known in the art.

The polyamide layer is applied such as the art is also for Polyolefmschicht, for example by means of hose or wrapping extrusion. In one possible variant, the polyamide layer can be applied together with a likewise Polyolefϊnschicht generated and applied by coextrusion of a multilayer composite.

The outer diameter of the metal pipe is preferably at least 25 mm and a maximum of 4800 mm, and more preferably at least 32 mm and a maximum of 2500 or 1500 mm.

The individual pieces of pipe are intended connected to a pipeline.

The pipeline in question, a transport line, a distribution line or service line be and be designed either as a line or as a gravity sewer. It is used, for example, the transport of district heating, fresh water, sewage, gas, air, oils, such as crude oil, light oil or heavy oil, fuels such as kerosene or diesel, petrochemicals, brine, lyes, or abrasive media, recovery or injection materials or dusts and can, for example, be a supply or disposal pipe.

The pipeline is laid without trenches and / or sand beds free by known methods.

Examples include horizontal drilling, the pipe bursting, plowing, milling and micro-tunneling. The horizontal drilling ( "Horizontal Directional Drilling"; HDD method) is a grave loose piping method in which first a controlled pilot bore is being driven on to be drilled path Then it expanded in one or more operations Thereafter, the pulled in tubing of the target pit.. from drawn into the drill hole. the HDD method is, for example, at river crossings, used crossings of paved areas, landings in the coastal area or mountain crossings. the prior art currently allowed drilling lengths up to 3000 m. the process is such. as the DVGW described by the GW 321st

The pipe bursting is a grave-impact method for pipe renewal, in which the old

Pipeline route is used. The old pipe is destroyed and confiscated the new pipeline to the existing route. After insertion of the rod into the old pipe the bursting head or the roller cutter is attached to destroy the old pipe. An arranged behind expander increases the route to the desired diameter. Here to increase the initial nominal size is possible. The Neuleitung is drawn simultaneously with bursting and expander. The burst lining is described in the leaflet RSV 8 of Pipe Rehabilitation Association e. V..

When plowing the plow cuts with his sword an installation slot in the ground. Displacing presses apart the ground. In the same work step, the tube is introduced into the slot. The tube lane is then closed again immediately. In this method, the laying depth is limited to about 2 meters.

When milling a narrow trench is cut by a special device, in which the tube is placed in the same operation. The excavated soil is used as backfill. The cutter can be used up to a burial depth of about 2 meters. For plowing and milling is currently a DVGW in development (GW 324).

Under Microtunneling means a remotely operating process for the propulsion of tubes, in which, starting from a starting shaft (press pit) by means of a propulsion unit with press and drill a channel tube is advanced. The soil is thereby degraded via a hydraulically driven drill head. To reduce the friction and to short-term support of the soil against burglary is in the head a conveying medium (in case of loose, non-cohesive soil Bentonitflüssigkeit; sufficient for cohesive or rocky ground water) is injected. Overburden is via screw conveyors and lines, which run already pressed tube, promoted in the press pit and from there upwards (above ground). Here, a separation between the floor and liquid. The fluid is then reused.

Incidentally, the IRB Literaturdokumentation 3366, "grave pipe installation" (Publisher: Fraunhofer Information Centre for Planning and Building IRB, Stuttgart) was, ISBN 978-3- 8167-3291-4, Fraunhofer IRB Verlag referenced.

Due to the high mechanical strength, good abrasion resistance, very high scratch resistance and the optimum thickness of the applied layer of polyamide, a good corrosion protection and the need for grave loose and sand beds laying techniques resistance strength of the outer shell can be simultaneously ensured in accordance with the invention.