DE9111403U1 - Multilayer plastic pipe and device for its manufacture - Google Patents

Description

Multilayer plastic pipe and device for its manufacture

The subject matter of the invention is a multi-layered pipe made of plastic according to the preamble of claim 1 and a device for producing the pipe according to the preamble of claim 12. Pipes according to the invention are used in particular as sewer pipes for waste water or cables.

A pipe and a device for its manufacture of the type mentioned above are already known from EP-A-0 385 465. The pipe is constructed in two layers, with the smooth inner pipe surface being part of a compact

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Attorney: admitted to the Hamburg courts

Deutsche Bank AG Hamburg, No. Cf5/284«v7 (bank code 200 fOO 0&THgr;) · Postgiro Hamburg 28 42-206 Dresdner Vank.AG tfa.mb^g.'Nr. 933 OO 35-JBLZ 200 800 00)

inner pipe. With the appropriate ring stiffness, such a pipe has a weight saving of around 50% compared to a compact pipe. However, if the pipe is to have certain inner and outer diameters - especially in order to adapt to standard dimensions - then the use of compact material is required that exceeds that required for strength reasons. Recycled material is not used for this pipe because of its impurities, which could affect compliance with the required strength, surface and durability values. However, original raw materials are relatively expensive compared to recyclable material. The composite pipe is extruded using a pipe head extrusion tool, which an extruder feeds with a compact plastic melt. In the tool, the melt is divided into two tubular mass flows, the outer of which is profiled in a corrugator and connected to the smooth inner mass flow. Such a device is described in DE-C-29 11 833 or EP-A-O 243 516. It is used primarily for PVC pipes because it does not allow the plastic mass to linger, which triggers the well-known thermal decomposition processes (burners).

It is also known to produce a plastic pipe with a smooth and compact inner and outer pipe.

between which an intermediate pipe is arranged. The intermediate pipe can be made either from original raw materials or foamed and compact from recycled plastics. PVC can be used as a raw material. However, especially when made from polyolefins (PE and PP), the pipe is manufactured using multi-layer extrusion technology, which is also common in the extrusion of plates or profiles using a feed block. The previously known pipe has a relatively high weight for the required ring stiffness.

Based on this, the invention is based on the object of creating an improved pipe that has a reduced weight for certain dimensions and the strength properties and resilience required for the intended use and also enables the use of recycled plastic. Furthermore, a device for producing the composite pipe, in particular from PVC, is to be created.

The solutions to this problem are specified in claims 1 and 12. Embodiments can be found in subclaims 2 to 11 and 13.

In a multilayer pipe according to the invention

So between the smooth inner pipe surface and the corrugated and compact outer pipe there is an intermediate pipe connected to the inner pipe surface and the outer pipe, which has a different quality than the outer pipe. Different quality means in particular that it has a different structure or a different material composition. The intermediate pipe can have a foam structure, which gives it additional insulating properties. The foamed or compact intermediate pipe can be made of a recycled material such as PVC bottle shredder or of a completely different material than the outer pipe. In all cases the intermediate pipe also ensures that the wall of the line pipe is reinforced without the relatively expensive use of compact outer pipe material having to be increased. This is especially true if the inner pipe surface is part of a compact inner pipe, which also requires a relatively expensive use of material. In terms of strength and durability, the outer pipe and, if applicable, the inner pipe are decisive for the line pipe, with the intermediate pipe providing not only a certain amount of strength, but also the necessary wall thickness. If it is made of recycled material, the intermediate pipe contributes to the disposal of plastic waste, the composition of which does not allow it to be used in conventional pipes with comparable properties.

leaves.

If the intermediate pipe is foamed, it can at least partially engage the corrugations of the outer pipe, thereby improving the bond between the various pipe layers and the insulating effect. Celuka foam is then preferably used. According to the patent publication mentioned at the beginning, the pipe can have thickened sections in the end area to form a socket or spigot, which can be formed primarily by the foamed intermediate pipe. In a foamed intermediate pipe, the inner pipe surface can be a smoothed inner surface of the intermediate pipe. In this case, a compact inner pipe is not required, whereby the resulting foam can be given a greater density by cooling on a tool mandrel and can be compact in an inner layer enclosing the inner pipe surface. Such a pipe is particularly suitable as a cable protection pipe in which the stress on the inner pipe surface is unproblematic due to the lack of a medium flowing through it, the pulling in of cables must be guaranteed and the desired ring stiffness is contributed primarily by the compact outer pipe.

An adhesive can be used between the outer pipe and the intermediate pipe.

...IS

ler, especially if they consist of different materials. The outer pipe, intermediate pipe and/or inner pipe can be made of PVC, PE and/or PP. For example, all pipe layers can be made of the same material, with the intermediate pipe having a foam or compact structure and consisting of original or recycled plastic. However, the above preferred plastics can also be combined in a conduit pipe, with different pipe layers being made of different plastics.

The device according to the invention for producing the line pipe combines the previously known composite pipes with the multi-layer extrusion technology. For this purpose, the mass flow for the intermediate pipe and, if necessary, for an adhesion promoter is applied by an extruder provided through the torpedoes of the extrusion tool to the divided mass flow for the inner pipe. The torpedoes, which are intended anyway for holding the mandrels or sleeves of the tool, are therefore used for the multi-layer extrusion of the intermediate pipe. Conventional technology can thus be prepared for the production of the pipe according to the invention with relatively minor changes.

Further details and advantages of the subject matter of the

...The

The invention is based on the following description of the associated drawings, which show various pipes and a device for their production. The drawings show:

Fig. 1 Pipe with inner pipe, intermediate pipe and outer pipe in a partial section through the pipe wall;

Fig. 2 Pipe with inner pipe, intermediate pipe, bonding agent and outer pipe in a partial section through the pipe wall;

Fig. 3 Pipe with intermediate pipe made of foam and smooth inner surface and outer pipe in partial section through the wall;

Fig. 4 Line pipe with smoothed inner surface and intermediate pipe made of foam filling the corrugated outer pipe in partial section through the pipe wall;

Fig. 5 Pipe with foamed intermediate pipe and outer pipe in a partial section through the wall at the pipe end;

Fig. 6 Extrusion head of the device for producing the duct pipe in a half section;

Fig. 7 Corrugator for producing the line pipe in half section.

In the various embodiments, the corresponding elements have been designated with identical reference numerals.

According to Fig. 1, the pipe has an inner pipe 1 with a smooth inner pipe surface 2, a corrugated outer pipe 3 and an intermediate pipe 4 arranged between the inner pipe and the outer pipe and connecting them. The intermediate pipe 4 is made of foam. The various layers are pressed together at the contact points when heated and are consequently welded together. The intermediate pipe 4 promotes the insulating properties and gives the pipe additional wall thickness without excessively increasing its weight. Strength and durability are determined primarily by the outer pipe 3 and the inner pipe 1. Large-dimensioned sewer pipes, e.g. from DN 160, can be structured in this way.

In the variant of Fig. 2, compared to Fig. 1, additional

An adhesion promoter 5 is arranged between the outer tube 3 and the intermediate tube 4, which promotes a connection between different materials of the outer tube and the intermediate tube. Transparent adhesives are known from film technology for the adhesion promoter 5.

The embodiments do not show a line pipe with a compact intermediate pipe 4, although this is also part of the subject matter of the invention. A recycled material can be used for both the compact and the foamed intermediate pipes.

Fig. 3 shows another pipe whose outer pipe 3 is connected internally to a foamed intermediate pipe 4. This cellular or foam layer is a freely expanding foam produced using chemical blowing agents, which is slowed down, compacted and cooled on the corresponding cooling mandrel surface or on adjacent compact pipe walls. Such a foam is available under the trade name "Celuka". An inner pipe surface 2 is not formed here on an inner pipe, but on an inner surface of the intermediate pipe 4. For this purpose, a thin layer of the inside of the intermediate pipe 4 is compacted and smoothed on a cool mandrel.

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Fig. 4 shows a pipe similar to that in Fig. 3, whereby the foam of the intermediate pipe 4 made of Celuka engages in the corrugations of the outer pipe 3 due to expansion. The inner pipe surface 2 is in turn formed on a compact layer of the intermediate pipe 4. This variant has particularly good insulation properties, including against sound transmission, and can be used as a cable protection pipe or house drain pipe, similar to Fig. 3. If durability and abrasion resistance of the pipe interior are important, the variant in Fig. 4 can also be provided with an inner pipe.

Fig. 5 shows the end of a pipe, which otherwise corresponds to that of Fig. 3. At the end 6, the intermediate pipe 4 is thickened, whereby the pipe has no corrugation on the outside there. This shape is created by smoothed mold jaws 7 of the corrugator, which is also shown. In the smoothed mold jaws, the thickened end 6 for the spigot end or socket is achieved by foaming the intermediate pipe material. The pipe can also be cut into individual pieces inline and one end 6 can be widened to form a socket. This technology is already described in the patent application mentioned at the beginning.

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According to Fig. 6, an extrusion tool 8 for the manufacture of line pipes has a head section 9 in which a plastic melt 10 fed in by an extruder is split into two mass flows 11, 12 for the outer pipe and inner pipe. The extrusion head 9 holds outer sleeves 13, 14 and inner sleeves 15, 16 and a central main mandrel 17, with torpedoes 18, 19 being provided for fixing the position of the inner sleeves 15, 16 and main mandrel 17. The mass flows 11, 12 are guided in the extrusion tool between the outer sleeves 13, 14, inner sleeves 15, 16 and main mandrel 17 in such a way that the mass flows do not linger anywhere and the PVC does not thermally decompose.

A secondary mass flow 20 for the intermediate pipe and 21 for the adhesion promoter are fed to the extrusion tool 8 by provided extruders, which are evenly distributed over the outer circumference of the mass flow 12 for the inner pipe through radial and annular channels of the torpedoes 18, 19.

Thus, in the extrusion tool, the known composite pipe extrusion technique is used with regard to the main mass flow 10 and the divided mass flows 11, 12 and the known multi-layer extrusion process is used with regard to the divided mass flow 12 and the secondary mass flows 20, 21.

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- 12 carried out.

The separated and superimposed mass flows 11, 12, 20, 21 are fed from the head of the extrusion tool 8 to a corrugator 22 as shown in Fig. 7. The outer compact mass flow 11 is fed into the mold jaws 23 of the corrugator after it leaves the tool by means of supplied compressed air or in a vacuum process, where it is demolded and cooled. The separated mass flow 12 with the coextrudate 20 and bonding agent 21 applied to the outside is smoothed on a cooling mandrel 24 and welded to the now profiled mass flow 11 at approximately 25 by means of pressure from the corrugator mold jaws 23 resting on it at the lowest point of the latter, whereby the bonding agent 21 exerts its bonding-promoting effect. The result is a pipe as shown in Fig. 2 as an endless pipe with inner pipe 1, intermediate pipe 4, bonding agent 5 and outer pipe 3.

.../13

Claims (13)

- 13 claims 1. Multi-layered plastic pipe, in particular for waste water or cables, with a smooth inner pipe surface (2) and a corrugated and compact outer pipe (3) connected thereto, characterized in that an intermediate pipe (4) connected to the inner pipe surface and the outer pipe and having a different structure than the outer pipe (3) is arranged between the inner pipe surface (2) and the outer pipe (3). 2. Pipe according to claim 1, characterized in that the intermediate pipe (4) is foamed. 3. Pipe according to claim 2, characterized in that the foamed intermediate pipe (4) engages at least partially from the inside into the corrugations of the outer pipe (3). 4. Pipe according to claim 2 or 3, characterized in that the foamed intermediate pipe (4) consists of a foam produced by means of chemical blowing agents, freely expanding and braked on a cooling mandrel surface or adjacent pipe wall, compacted and cooled. .../14 5. Pipe according to one of claims 2 to 4, characterized in that the foamed intermediate pipe (4) is thickened at at least one pipe end (6). 6. Pipe according to one of claims 2 to 5, characterized in that the inner pipe surface (2) is a smooth inner surface of the foamed intermediate pipe (4). 7. Pipe according to one of claims 1 to 5, characterized in that the inner pipe surface (2) is a smooth inner surface of a compact inner pipe (1). 8. Pipe according to claim 7, characterized in that the intermediate pipe (4) has a different structure than the inner pipe (1) and is compact. 9. Pipe according to one of claims 1 to 8, characterized in that the intermediate pipe (4) contains a recycled material. 10. Pipe according to one of claims 1 to 9, characterized in that an adhesion promoter (5) is arranged between the outer pipe (3) and the intermediate pipe (4). 11. Pipe according to one of claims 1 to 10, characterized .../15 characterized in that the outer pipe (3), intermediate pipe (4) and/or inner pipe (1) are made of PVC, PE and/or PP. 12. Device for producing a multilayer pipe according to one of claims 1 to 11, with a composite pipe extrusion tool (8) fed by an extruder for dividing a main mass flow (10) into two mass flows (11, 12) for the outer pipe and inner pipe and a downstream corrugator (22) with mold jaws (23) for producing a corrugation of the mass flow (11) for the outer pipe (3) and a cooling mandrel (24) for cooling the mass flow (12) for the inner pipe (1) and connecting it to the outer pipe, characterized in that a secondary mass flow (20) for the intermediate pipe (4) is applied by an extruder through a torpedo (18) of the tool to the divided mass flow (12) for the inner pipe (1) on the side facing the divided mass flow (11) for the outer pipe (3). 13. Device according to claim 12, characterized in that a secondary mass flow (21) with the adhesion promoter from an extruder through a torpedo (19) of the tool (8) is applied to the mass flow (20) for the intermediate pipe (4) on the side facing the mass flow (11) for the outer pipe (3).