WO2017036462A1

WO2017036462A1 - Method for producing a multi-layered composite pipe

Info

Publication number: WO2017036462A1
Application number: PCT/DE2016/100399
Authority: WO
Inventors: Brian Corley
Original assignee: Inoex Gmbh
Priority date: 2015-09-02
Filing date: 2016-09-01
Publication date: 2017-03-09
Also published as: DE102015114637B3; CN108136465B; CN108136465A

Abstract

The invention relates to a method for producing a multi-layered composite pipe which comprises: a central metallic barrier layer for blocking penetration of gas; a medium-guiding inner layer; and an outer protective layer, in which: said metallic barrier layer is designed as a barrier layer that is closed in the peripheral direction, or as a metal pipe; the inner layer is extruded into the tubular barrier layer by means of an internal main extruder, an internal starting material being fed to said internal main extruder; and the outer protective layer is extruded onto said barrier layer by means of an external main extruder, an external starting material being fed to said external main extruder. According to the invention, a length/weight (LM1) of the composite pipe can be controlled, said control comprising at least the following steps: specifying a total throughput (n, rs) as the sum of an internal throughput (n2, rs2) of the internal starting material and an external throughput (n6, rs6) of the external starting material (St1); controlling an outer diameter of the protective layer by measuring the outer diameter and adjusting the external throughput (n6, rs6) for the protective layer (St2, St3, St4, St5); determining the internal throughput (n2, rs2) from the total throughput (n, nm) and the adjusted external throughput (n6, nm6) (St6); and adjusting the internal throughput (n2, rs2), (St6, St7, St8, St9).

Description

Method for producing a multilayer composite pipe

The invention relates to a method and an apparatus for producing a multilayer composite pipe. Such a composite pipe is used in particular for conducting liquids or gases which are to be sealed securely against the environment or the outside space. The composite tube in this case has a central metallic gas barrier layer, in particular oxygen barrier layer, the z. B. is formed of aluminum. The middle metallic barrier layer thus forms a metal tube which securely blocks a gas passage in the radial direction. Radially inside the barrier layer or the metal tube, a medium-conducting inner layer is formed, which is designed for example as a water-removing inner layer for aqueous media or to guide other liquids such as gasoline, solvents, etc. On the metallic barrier layer or the metal tube, an outer protective layer is applied. The medium-carrying inner layer and the outer protective layer are generally extruded as plastic layers, for example made of polyethylene or else polyamide. For better adhesion, an inner adhesion promoter layer is applied between the metallic barrier layer and the medium-guiding inner layer; For example, when using polyethylene as the material for the inner media-carrying layer, the inner primer layer may be polyethylene-based. Accordingly, an outer adhesion promoter layer is applied to the outer side of the metallic barrier layer for adhesion promotion to the outer protective layer. The production of the entire plastic-metal composite pipe can be made in a single-stage manufacturing process in which a metal band formed and longitudinally welded sicherheitsüberlappt, butt welds in some cases without overlap to form the metal tube and immediately following the inner primer layer and the inner layer in the metal tube and further extruding the outer primer layer and protective layer onto the metal tube. Here, advantageously, the same or very similar plastics for inner and outer layers are used.

Thus, in this single-stage manufacturing process, the metal forming and the extrusion of the other layers take place in quick succession, by forming the metal strip around an extrusion tool around the pipe and z. B. is welded overlapped and the two inner layers are extruded into the freshly shaped metal strip and the two outer layers are extruded onto the freshly shaped metal tube.

EP 0353977 A1, EP 0581208 A1 and WO 00/44546 A1 describe such composite pipes and methods and devices for their production.

Process critical for this production process are in particular the shaping and the overlapping welding of the metal strip. Fluctuations in the molding process lead to a different width of the overlap and thus to a fluctuation in the diameter of the metal tube.

A modified process for producing a plastic-metal composite pipe is described in EP 1986798 A1. In this case, the metal layer is not produced by a shaped and welded strip, but instead is seamlessly extruded by pressing a metal wire through a shaping die. trudiert. Again, the production process is subject to fluctuations that lead to fluctuations in the dimensions of the metal layer.

Since the inner layers and outer layers are extruded in-line in the single-stage production processes with fixed material throughputs in the process, a fluctuating diameter of the metal layer correspondingly means a fluctuation in the entire pipe diameter, while the wall thickness of the individual layers continues to fluctuate. The variations in the outer diameter of the metal tube are for example in the range of up to 0.2 mm, which can lead to a very high reject rate in the manufacturing process with permissible total tolerances for the outer diameter of the composite pipe of 0.15 mm. However, process engineering measurements and checks in such a one-step process are very problematic. The metal layer generally prevents measurement of the inner layers, except by elaborate methods such as X-ray studies.

In principle, gravimetric dosages are known in the supply of a plastic starting material for plastic pipes, in particular multilayer plastic pipes. Such gravimetric dosages generally control the mass flow rate of the extruders, ie the delivery rate of the starting material. In conjunction with the measurement or regulation of the speed at which the pipe is produced, a length weight control (meter weight control) is thus possible.

Furthermore, external calibrations for fixing an outer diameter of a pipe are known. For a metal-reinforced plastic pipe, however, an external calibration is not possible because the rigid metal layer does not allow the plastic melt to be applied to a calibration. In order to remain within the allowable tolerances for outer diameter and inner diameter of the tube despite the varying diameter of the inner metal layer, the medium-carrying inner layer and the outer protective layer are generally formed as a compromise with a wall thickness in the middle of the tolerance field. In this case, however, more material is used than necessary, and greater fluctuations in the diameter of the inner metal layer still lead to exceeding or falling below the permissible tolerances for the composite pipe.

The invention has for its object to provide a method and apparatus for producing a multilayer composite pipe, which allow safe and yet material-saving production.

This object is achieved by a method according to claim 1 and an apparatus according to claim 19. In this case, furthermore, the composite tube producible by the method is created.

The inventive method can be carried out in particular with a device according to the invention. The device according to the invention can be provided in particular for carrying out a method according to the invention.

According to the invention, a control method is thus provided in which the external throughput for forming the outer protective layer and the inner throughput for the formation of the medium-guiding inner layer are adjusted or metered, the throughputs being included in the control. In this case, the outer protective layer is initially regulated by the metrologically well-feasible measurement of an outer diameter of the outer protective layer, which thus advantageously also represents the outer diameter of the entire composite tube. In this case, a regulation of the outer throughput of the outer protective layer takes place by measuring the outer diameter and adjusting the outer throughput. Subsequently, the inner throughput of the inner layer is adjusted as a function of the previously regulated, current outer throughput. Thus, an inner target throughput for the inner layer can be formed and adjusted currently depending on the regulation of the outer protective layer. The adjustment of the internal throughput can be done by a control or even simple difference formation.

According to the invention, it is thus recognized that reliable and material-use-reducing control is already possible by way of reliable measured variables, namely the outer diameter of the outer protective layer or of the composite tube and an inner throughput and outer throughput, without the Example, a direct measurement of the inner layer by X-ray and other expensive, expensive process is required. According to the invention, some advantages are achieved. The overall

Length weight of the composite tube can be kept low and safely controlled according to the invention. With an increase in the wall thickness of the outer protective layer, a reduction in the wall thickness of the inner layer can accordingly be set directly in order to adjust the overall length weight, and vice versa, an enlargement of the wall thickness of the outer protective layer can be achieved. thickness of the inner layer can be adjusted. Thus, the cost of materials, weight and costs are reduced. In addition, tight manufacturing tolerances can be maintained and production scrap can be avoided.

Furthermore, the method and the device according to the invention can be exercised with little effort, since dosages, in particular gravimetric dosages for the inner layer and the outer protective layer, are generally customary anyway and the inclusion of the determined throughputs does not require any relevant metrological effort. Also, a measurement of the outer diameter is connected by, for example, a (laser) optical measuring device with no major effort.

By such optical measurement can also rather

Out of roundness or ovality can be determined and checked by measuring at several circumferential positions, so that a further quality assurance is possible.

The composite pipe designed in accordance with the invention is therefore distinguished, in particular, by a high constancy of its layers and, in particular, its overall length weight. It can thus be formed thin-walled at predetermined tolerances, or be made with very tight tolerances.

According to an advantageous embodiment, first of all a total throughput for the two main extruders, that is to say the inner main extruder for extruding the inner layer and the outer main extruder for extruding the outer protective layer, is determined and set as default. This total throughput can be determined in particular directly from the required total length weight (total meter weight) of the composite pipe. The contribution of the length weight of the

Metal tube is known, for example, in an overlapped by welding a metal strip made of metal strip - regardless of the width of the overlap - by the supplied metal strip. From the outer throughput set in the first control method while measuring the outer diameter of the protective layer, an actual set value for the inner throughput can then be formed as difference formation between the predetermined total throughput and the current outer throughput, which thus follows, for example, by activation the screw speed of the inner main extruder is set or adjusted.

The adjustment of the inner throughput and outer throughput can be done in different embodiments. One embodiment uses gravimetric metering via weighing devices that weigh a continuous feedstock and thus determine a feed rate as a mass per time. The feeding can be done in free fall, so that the starting material, for example a plastic powder, plastic granules or plastic pellets, from reservoirs on the respective weighing device to the main main extruder or external main extruder drops, whose speeds are permanently controlled so that the desired inner and Outer throughput is achieved exactly. In such an embodiment, the total throughput can thus be set as total delivery rate of dimension mass per time.

According to a further embodiment, melt pumps which are inserted between the respective extruder screw and the extruder nozzle (annular gap nozzle for extruding the annular material) can be used for the two main extruders. Such melt pumps can be designed in particular as gear pumps and are characterized by a very constant, speed-independent volume flow rate and thus also mass throughput per revolution. If identical melt pumps are used for the main inner extruder and the outer main extruder, the total throughput can thus be set as the total speed, that is to say the sum of the inner and outer rotational speeds; otherwise melt pumps with different throughput per revolution can also be used, using an adjustment factor to determine the total throughput. Thus, the melt pumps are controlled by the control signals of the control device and set corresponding speeds. It is recognized that z. B. a control of the rotational speeds of the extruder screws may not be sufficient without additional gravimetric weighing of the throughput, as these mass flow rates are not sufficiently independent of speed, but are influenced by the back pressure upstream of the extruder nozzle or a return flow from the extruder nozzle.

Furthermore, it is recognized that in many embodiments inclusion of the primer layers is initially not required because they do not contribute to the relevant extent to the total length weight and variations of the metal pipe also do not affect a relevant extent in a change in their wall thickness.

Alternatively, or with special training, however, the regulation of the adhesive layers can be included.

The invention will be explained in more detail below with reference to the accompanying drawings of some embodiments. 1 is a perspective, sectional view of a five-layer composite tube according to an embodiment of the invention; FIG. 2 shows a device for producing the composite pipe; FIG.

3 shows a flowchart of a method according to the invention for producing the composite pipe; and

Fig. 4 is a comparison with FIG. 2 modified embodiment.

A five-layer composite pipe 1, according to Figure 1 - from the inside to the outside - a media-leading, z. B. water-bearing, inner layer 2 of, for example, polyethylene, an applied on the inner layer 2 inner primer layer 3 with a thickness of, for example, b3 = 0, 15 - 0.2 mm, an applied on the inner adhesion promoter layer 3 oxygen barrier layer 4 of a Metal, in particular aluminum, an applied on the barrier layer 4 outer adhesive layer 5 and an applied on the outer adhesive layer 5 outer protective layer 6 in turn, for example, on polyethylene. The layers 2, 3, 4, 5, 6 are thus each tubular in themselves, they have outer diameters d2, d3, d4, d5, d6 and layer thicknesses (wall thicknesses) b2, b3, b4, b5, b6.

The adhesion promoter layers 3 and 5 serve to promote the adhesion of the middle, metallic barrier layer 4 with the respective plastic layer, that is to say the inner layer 2 or the protective layer 6, and are formed, for example, from a polyethylene-based material. When using the composite tube 1 for more aggressive liquids, for example as a gasoline line, the inner layer 2 can also be made of polyamide, for example. The barrier layer 4 is formed in the illustration shown as a safety overlapped longitudinally welded tube; the further layers 2, 3, 5 and 6 are extruded. The production is advantageously carried out in a single-stage production process with a device 8 shown in FIG. 2 for producing the five-layer composite pipe 1.

The aluminum forming takes place in a forming device 10, which is a metal semi-finished 1 1, z. B. an aluminum strip is fed continuously. The metal semi-finished product 1 1 is in this case formed around an extrusion tool 14 indicated in FIG. 2 around the metal tube, that is to say to the tubular barrier layer 4. If a metal band used so it is either formed with an overlap 13 and welded in a weld 12 overlaps or without overlap 13 with only one

Weld 12 butt welded.

The inner primer layer 3 and the media-carrying inner layer 2 are extruded into the freshly shaped tubular barrier layer 4. The outer primer layer 5 and the outer protective layer 6 are extruded onto the tubular barrier layer 4.

The extrusion die 14 is shown schematically in broken lines in FIG. 2 and has individual extruders 14-i with i = 2, 3, 5, 6 for the layers 2, 3, 5, 6, each of which has an extruder screw 15-i and a nozzle 16-i, with i = 2, 3, 5, 6 having an annular gap to form the layers 2, 3, 5, 6 as ring layers around the barrier layer 4. In this case, the nozzles for the two outer plastic layers as well as for the two inner plastic layers are usually designed in each case as coextrusion nozzles. Such a single-stage production process is subject to fluctuations and tolerances. Process critical is already the formation of the metal tube from the metal semi-finished 1 1. Thus, in the case of forming and welding a metal strip, variations in the width of the overlap 13 and the width of the weld 12, respectively, lead to variations in the diameter d4 of the barrier layer 4, ie, the metal tube. Since the inner layers 2 and 3 and the outer layers 5 and 6 are extruded in-line in the process, a fluctuation of the diameter d4 of the barrier layer 4 - without an adaptation of the layer thicknesses b2 of the inner layer 2 and b6 of the protective layer 6 - results in a fluctuation of the Through the device of Figure 2 and the method of Figure 3, it is possible, the length-weight (meter weight, mass per unit length) LM1 of the Compound 1 within the allowable control deviations to regulate, with a larger diameter d4 of the barrier layer 4, the length weight LM6 of the outer protective layer 6 is reduced and the length weight LM2 of the inner layer 2 is increased.

Accordingly, with a smaller diameter d4 of the barrier layer 4, the length weight LM6 of the outer protective layer 6 is increased and the length weight LM2 of the inner layer 2 is reduced.

The main extruders 14-2 and 14-6 of the inner layer 2 and the outer protective right 6 are assigned a gravimetric dosage. According to FIG. 2, inner feed material 20, for example a plastic granulate, plastic powder or plastic pellets, is removed from a supply store 21 and fed via an internal weighing device 24 to the main main extruder 14-2. The inner weighing device 24 of the inner main extruder 14-2 determines the feed rate sr2, for example, a time feed amount as mass per time (kg / h), and outputs a first measurement signal S1 to a controller 30. The feed material 20 is subsequently fed to the inner main Extruder fed 14-2, taken up by this, melted, fed through its extruder screw 15-2 to its nozzle 16-2 and squeezed out. The speed of the extruder screw 15-2 determines the feed rate sr2.

The same applies to the outer main extruder 14-6: starting material 35 is fed from a supply store via an external weighing device 42 to the outer main extruder 14-6, wherein the outer weighing device 42 outputs a second measuring signal S2 to the control device 30.

The control device 30 in turn outputs a first control signal S3 to the inner extruder screw 15-2 and a second control signal S4 to the outer extruder screw 15-6, each for setting one of the rotational speed and thus the feed rates sr2 and sr6.

Furthermore, a measurement of the formed composite pipe 1, z. Example, as a multi-axis outer diameter measurement, in particular laser measurement with an optical measuring device 50 preferably three or more circumferentially distributed positions, so that not only an average outer diameter d6 of the outer protective layer 6, but optionally also an ovality or out-of-roundness can be determined. The measuring device 50 thus outputs a third measuring signal S5 to the control device 30, which is used to correct the length weight LM6 of the outer protective layer 6. The adhesion promoter layers 3, 5 are not regulated in this embodiment. Their training takes place via the secondary extruders 16-3 and 16-5. This can be done without the use of gravimetric dosing by setting constant speeds of the extruder screws 15-3 and 15-5. When gravimetric doses are also used for the secondary extruders 16-3 and 16-5, the starting material 33 of the inner adhesion promoter layer 3 is fed via a weighing device 22 to the inner secondary extruder 16-3 or from the inner secondary extruder 16-3 according to the rotational speed of its extruder screw 15-3. 3, and outputs a measurement signal S6 to the controller 30, which in turn outputs a control signal S7 to the inner slave extruder 16-3. Here, it is preferable to specify a constant feed rate sr3 of the starting material 33 and to keep it constant via the actuating signal S7. Correspondingly, starting material 34 of the outer adhesive layer 5 is fed via a weighing device 43 to the outer secondary extruder 14-5 and a measurement signal S6 of the weighing device 43 is output to the control device 30, which in this embodiment via the control signal S9 to the outer secondary extruder 14-5 a constant feed rate Set sr5. FIG. 3 shows the steps of the control method. After a start in

Step StO, in St1, a default for the total feed rate n formed as the sum of the inner feed rate n2 for the inner main extruder 14-2 and the outer feed rate n6 for the outer main extruder 14-6 is given.

n = n2 + n6.

Thereafter, in step St2, the actual outer diameter d6_ist of the composite tube 1 or the outer protective layer 6 is measured by means of the measuring device 50 and evaluated in step St3 in step St2. If according to of the left branch 3a, the outer diameter d6_ist is smaller than a lower limit d6_u, subsequently, according to step St4, by controlling the rotational speed for the extruder screw 15-6 by means of the second control signal S4, the outer feed rate n6 in kg / s to the outer main Extruder 14-6 increased; however, if it is determined according to the right branch 3b that the detected outer diameter d6 is larger than an upper limit d6_o, the outer feed rate n6 is reduced by the second set signal S4 in step St5. In both cases, again in step St2, the outer diameter d6_ist is measured again and subsequently evaluated in the decision step St3.

If, according to the lower branch 3c, a current outer diameter d6_ist is determined within the limits d6_u, d6_o in step St3, then the adjustment of the inner feed rate n2 for the inner main extruder 14-2 to the currently set outer takes place in steps St6 to St9 Feed rate n6 according to

n2 = n - n6.

This is shown in FIG. 3 as regulation of the feed rate n2.

For this purpose, in step St6, first of all, from the total feed rate n set in step St1 and the feed rate n6 set in steps St2-St5, a desired value n2_soll for the inner feed rate n2 of the inner main extruder 14-2 is determined from n2_soll = n - n6_ist, with n6 as the currently set external feed rate. The set value n2_soll is subsequently set in steps St7, St8 and St9 in turn to step St6, in particular regulated:

If it is measured in step St7 that the inner feed rate n2_act is too small by the inner main extruder 14-2, the inner feed rate n2 of the inner feed rate n2 of the inner feed rate n2_ist is calculated according to the left branch from step St8. increased in the main extruder 14-2; on the other hand, if it is determined in step St7 that the inner feed rate n2 of the inner main extruder 14-2 is too large, then, according to step St9, the inner feed rate n2 is reduced; The method is in each case led back to step St6. In step St7, a comparison is thus made as to whether

n2_u> n2_ist> n2_o is,

upon satisfaction of this condition, the method is subsequently reset before step St2. The steps St6 to St9 can thus in principle also be represented simplified as a difference formation n2 = n-n6.

By specifying the total feed rate n in step St1, the total length weight or total meter weight of the entire composite pipe 1 can thus be kept constant.

An increase in the outer layer thickness (wall thickness) b6 of the outer protective layer 6 thus leads directly to a reduction or reduction of the inner layer thickness b2 of the media-carrying inner layer 2, and vice versa.

FIG. 4 shows an alternative embodiment to FIG. 2. Referring to FIG. 4, the internal flow rate and external flow rate of the starting materials 20, 35 are adjusted to the main extruders 14-2 and 14-6, but via melt pumps 60, 61, the between the extruder screws 15-2 and 15-6 and the extruder nozzles (annular gap nozzles) 16-2 and 16-6 are installed. Such melt pumps 60, 61 are preferably operated with a constant melt pre-pressure from the extruder and are characterized by a very constant, speed-independent volume throughput per revolution, that is, in known or zurückgerechneter

Melt density also mass throughput per revolution. According to the second embodiment, the melt pumps 60, 61 are thus each driven in such a way via the inner actuating signal S3 and the outer actuating signal S4 that their respective rotational speed rs2, rs6 is set.

If the melt pumps 60 and 61 have the same design, a total rotational speed rs, which is the sum of the internal rotational speed rs2 of the inner main pump 60 of the internal main body 60, can be set in step St1 instead of the total supply rate n according to the flowchart in FIG Extruder 14-2 and external speed rs4 of

Melting pump 61 of the outer extruder 14-6 represents: rs = rs2 + rs6, so that in the flowchart of Figure 3 below in the first loop of steps St2 to St5 as a manipulated variable, the external speed rs6 is set to the outer diameter d6 in the allowable tolerance range and then, in steps St6 to St9, the internal speed rs2 = rs-rs6 is adjusted.

Are used for the inner layer 2 and the outer layer 6 plastics with different density p, i. an inner density p2 of the inner layer 2 and an outer density p6 of the outer layer 6, this can be taken into account in both embodiments via a correction factor p2 / p6.

Other embodiments may, as a modification to FIGS. 2 and 4, also include a regulation of the adhesion promoter layers 3 and 5. For the effect of the adhesion promoter layers 3 and 5, it is important that the thickness of the adhesion promoter layers 3, 5 is within a certain desired range, usually between 0.1 and 0.2 mm. Too thin a primer layer does not ensure sufficient adhesion between the layers, while too thick a primer layer carries the risk of a cohesive failure in the primer layer. For this reason, the primer layers 3 and 5 z. B. not proportional to the changes of the protective layer 6 and the media-carrying inner layer 2 adapted. It is advantageous, however, that the bonding layers 3 and 5, regardless of their position in the composite pipe 1, always have the same thickness (thickness) b3 or b5, ie more material upon displacement of an adhesion promoter layer and more material during a displacement of one of the adhesion promoter layers 3 , 5 less material is used inside.

According to a first embodiment, a more precise control of the adhesion promoter layers 3 and 5 can be carried out by calculating the position of the metal layer 4 in the composite tube, as described below as a modification of the embodiment of FIGS. 2 and 3. For this purpose, it is assumed that the adhesion promoter has a very similar density as the materials for outer layer 6 and inner layer 2. This is the case for most used for the applications linear low density polyethylene (LLDPE) or polyethylenes with increased heat resistance (PE-RT) and the chemically based adhesion promoters.

Instead of the throughputs n6 and n2, the throughputs of the two outer layers na and the two inner layers ni with the associated length weights LMa and LMi (in kg / m) are considered in the control loop according to FIG. 2 as: na = n5 + n6 ni = n2 + n3 and

LMa = LM5 + LM6 = (n5 + n6) / v

LMi = LM2 + LM3 = (n2 + n3) / v where v is the take-off speed of the composite pipe 1.

With a - by the control circuit described in Fig. 2 - determined

Material used for the outer layer na can be calculated permanently the exact position of the metal layer in the composite tube. The outer diameter d6 of the composite pipe 1 is known by the permanently measuring measuring device 50. With the length weight LMa and the material density p, the outer diameter d4 of the metal layer 4 (equal to the inner diameter di5 of the adhesion promoter layer 5) can be calculated:

LMa / p = π / 4 x (d6 ² -

Thus, it is easy to calculate which length weight LM5 and therefore which throughput n5 should be set by means of the gravimetry of the secondary extruder 14-5 for a given layer thickness b5 of the outer adhesion promoter layer:

LM5 = π / 4 x ((d4 + b5) ² -d4 ² ) xp The required length weight LM6 and thus also the throughput n6 for the protective layer 6 are thus calculated:

LM6 = LMa - LM5

Since the outer diameter d3 of the inner adhesion promoter layer 3 can be calculated at the same time by the known thickness b4 of the metal layer 4: d3 = d4-b4 can in analogous calculation for a given thickness b3 of the inner adhesion promoter layer 3, the length weights LM3 and LM2 and thus the throughputs n3 and n2 of the two inner layers 3 and 2 are determined.

Claims

claims

A method of producing a multilayer composite pipe (1) comprising a middle metal barrier layer (4) for blocking a gas passage, a medium-conducting inner layer (2) and an outer protective layer (6),

wherein the metallic barrier layer (4) is formed as a circumferentially closed barrier layer or metal tube, the inner layer (2) is extruded through an inner main extruder (14-2) into the tubular barrier layer (4), the inner main extruder (14-2) an inner starting material (20) is guided, and

the outer protective layer (6) is extruded onto the barrier layer (4) by an outer main extruder (14-6), wherein an outer starting material (35) is supplied to the outer main extruder (14-6),

characterized in that

a regulation of a length weight (LM1) of the composite pipe (1) is provided, wherein the control has at least the following steps:

Specification of a total throughput (n, rs) as the sum of an inner throughput (n2, rs2) of the inner starting material (20) and an outer throughput (n6, rs6) of the outer starting material (35) (St1),

Controlling an outer diameter (d6) of the protective layer (6) by measuring the outer diameter (d6) and adjusting the outer throughput (n6, rs6) for the protective layer (6) (St2, St3, St4, St5),

Determine the internal flow rate (n2, rs2) from the total flow rate (n, nm) and the set external flow rate (n6, nm6) (St6), and Adjust the internal flow rate (n2, rs2) (St6, St7, St8, St9).

A method according to claim 1, characterized in that the starting material (20) of the inner layer (2) and the starting material (35) of the protective layer (6) are each plastic material, preferably the same plastic material.

A method according to claim 1 or 2, characterized in that for forming the metallic barrier layer (4) a metal strip (1 1), for example aluminum strip, continuously formed into a closed tube and longitudinally overlapping wound and in an overlapping region (13) of its Connected edges, in particular in a weld (12) is longitudinally welded.

A method according to claim 1 or 2, characterized in that for the formation of the metallic barrier layer (4) a metal strip (1 1), for example aluminum strip, continuously formed into a closed tube and longitudinally butt-wound and connected in a joint area of its edges, in particular in a weld (12) is longitudinally welded.

A method according to claim 1 or 2, characterized in that to form the metallic barrier layer (4) a semi-finished metal product (11), for example aluminum wire, is extruded by pressing through a forming device 10, for example a nozzle, into a seamless tube.

Method according to one of the preceding claims, characterized in that

the specification of the total throughput (n, rs) is made by

- First, a total length weight (LM) of the composite tube (1) is given,

a sum of the length weights (LM2, LM6) of the inner layer (2) and the protective layer (6) is formed from the total length weight (LM) taking into account the length weight (LM4) of the barrier layer (4),

- From the sum of the length weights (LM2, LM6), a density of the solid starting materials (20, 35) of the inner layer (2) and the protective layer (6) and a withdrawal speed (v) of the composite tube (1) the total throughput (n, rs) is determined.

7. The method according to any one of the preceding claims, characterized in that the method for producing the multilayer composite pipe (1) is in one stage, wherein during or immediately after the formation of the barrier layer (4) as a closed tube, the inner layer (2) and the outer layer (6) are applied, preferably by an extrusion die (14) with extrusion nozzles (16-2, 16-6) formed as annular gaps, wherein the closed tube of the barrier layer (4) around the

Extrusion tool (14) is formed around.

8. The method according to any one of the preceding claims, characterized in that as inner flow rate (n2) an inner feed rate (n2) of the inner starting material (20) to the inner main extruder (14-2) and as an outer throughput (n6) a outer feed rate (n2) of the outer raw material (35) is set to the outer main extruder (14-6),

wherein the total flow rate (n) is formed as the total feed rate (s) formed as the sum of the inner feed rate (n2) and the outer feed rate (n6).

9. The method according to claim 8, characterized in that the inner starting material (20) via an inner weighing device (24), in particular an inner gravimetric weighing device (24), the inner main extruder (14-2) is supplied, wherein the inner Feed rate (n2) by controlling a speed of an internal

Extruder conveyor unit, z. B. an extruder screw (15-2), by means of an inner control signal (S3) is set.

10. The method according to claim 8 or 9, characterized in that the outer starting material (35) via an outer

Weighing device (42), in particular an outer gravimetric weighing device (42), the outer main extruder (14-6) is supplied, wherein the external feed rate (n6) by controlling a rotational speed of an outer extruder conveyor unit, for. B. an extruder screw (15-6) by means of an external control signal (S4) is set.

1 1. Method according to one of claims 1 to 7, characterized in that between an extruder conveyor unit, for. Extruder screw (14-2, 14-6), and an extruder nozzle (16-2, 16-6) of the main inner extruder (14-2) and the outer main extruder (14-6), one each Melting pump (60, 61) is provided, wherein the inner throughput as the inner speed (rs2) of the inner melt pump (60) and the outer flow rate as outer speed (rs6) of the outer melt pump (61) is set, and the total Throughput (rs) as the sum of the external speed (rs6) and the internal speed (rs2) is formed.

12. The method according to any one of the preceding claims, characterized in that the adjustment of the internal throughput (n2, rs2) is provided as difference formation or as a control, wherein an inner nominal throughput (n2_soll, rs2_soll) is first determined from the total throughput (n, rs) and the outer throughput (n6, rs6) set in the first control of the outer diameter (d6) of the protective layer (6) (St6 )

Subsequently, the current internal actual throughput (n2_act, rs2_ist) is compared with the internal target throughput (n2_soll, rs2_soll) (St7), and

Subsequently, depending on the comparison, the internal actual throughput (n2, rs2) is optionally adjusted (St8, St9).

13. The method according to any one of the preceding claims, characterized in that on the inside of the barrier layer (4) formed to the tube an inner adhesion promoter layer (3) is extruded, on which the inner layer (2) is extruded, and / or

on the barrier layer (4) an outer adhesive layer (5) is extruded, on which the outer protective layer (6) is extruded.

14. The method according to claim 13, characterized in that the inner adhesive layer (3) and / or the outer adhesive layer (5) in the regulation of the total length weight (LM) are not adjusted or changed.

15. The method according to claim 13, characterized in that the inner adhesive layer (3) and / or the outer adhesive layer (5) in the regulation of the total length weight (LM) are controlled with.

16. The method according to claim 15, characterized in that the adhesion promoter layers (3, 5) are regulated to predetermined wall thicknesses (b3, b5) by the current position of the metal layer (4) in the composite pipe (1) is determined

the outer diameter (d6) of the protective layer (6) measured with the measuring device (50)

the feed rates for the protective layer (6) and the outer adhesive layer determined by the weighing devices (42, 43)

(5) and

a take-off speed (v) of the composite pipe (1),

wherein, starting from the outer diameter (d6) of the composite tube (1) and an inner diameter (d3) of the metal layer (4), the further layer structure (2, 3, 5, 6) of the composite tube (1) with measured outer diameter (d6), predetermined wall thicknesses (b3, b5) of the adhesion promoter layers (3,5) and predetermined total length weight (LM1) is calculated. 17. The method according to any one of the preceding claims, characterized in that the measurement of the outer diameter (d6) (St1) as an optical measurement, for. B. laser-optical measurement of the outer diameter (d6) of the formed composite pipe (1), in particular over a plurality of circumferentially distributed locations to take into account an ovality.

18. Composite pipe (1), which is produced by a method according to one of the preceding claims. 19. Device (8) for producing a multilayer composite pipe (1), comprising:

- A control device (30) for receiving measurement signals (S1, S2, S5, S6, S8) and output of control signals (S3, S4, S7, S9),

- A forming device (10) for receiving a Metallhalbzeu- ges (1 1) and forming the metal semi-finished product (1 1) for generating a circumferentially closed tubular barrier layer

(4)

an extrusion die (14) having an inner main extruder (14-2) for extruding a medium-carrying inner layer (2) into the barrier layer (4) and an outer main extruder (14-6) for extruding an outer protective layer (14) 6) on the barrier layer (4) in a one-step extrusion process,

a measuring device (50) for measuring an outer diameter (d6) of the protective layer (6) and outputting a measuring signal (S5) to the control device (30),

wherein the control means (30) is adapted to control a rotational speed of an inner extruder feed unit (15-2) of the inner main extruder (14-2) by an inner actuating signal (S3), for adjusting an internal throughput of the inner Ausgangsmate- rials (20)

wherein the control device (30) is designed to control an external speed of an extruder feed unit (15-5) of the outer main extruder 15-6 by an external control signal (S4) for setting an external flow rate of the outer starting material (20 )

wherein the control device (30) is designed to control a length weight (LM1) of the composite tube (1),

the control having at least the following steps:

Specification of a total throughput (n, rs) as the sum of an internal throughput (n2, rs2) of the inner starting material (20) and an outer throughput (n6, rs6) of the outer starting material (35),

Controlling an outer diameter (d6) of the protective layer (6) by measuring the outer diameter (d6) and adjusting the outer throughput (n6, rs6) for the protective layer (6), Determine the internal flow rate (n2, rs2) from the total flow rate (n, nm) and the set external flow rate (n6, nm6), and

Adjustment of the internal flow rate (n2, rs2).