DE102017217544A1 - Piping and method of manufacture - Google Patents

Abstract

The invention relates to a pipe made of plastic and a method for producing a pipe (10) having a cross-sectional three-layer structure (11), wherein the structure at least one outer layer (13), an inner layer (14) and an intermediate middle layer (15) wherein the middle layer contains fibers, wherein the plastic of the outer layer, the inner layer and the middle layer is polyethylene (PE).

Description

The invention relates to a pipeline and a method for producing a pipeline made of plastic with a three-layer cross-sectional structure, wherein the structure has at least one outer layer, an inner layer and an intermediate middle layer, wherein the middle layer contains fibers.

Plastic pipes can be designed in the form of an extruded, injection-molded or blow-molded pipe and serve to create pipe networks for liquid, pasty or gaseous media. Plastics pipelines are widely used in the field of drinking water supply, heating technology, the food industry, apparatus engineering and the chemical industry. In particular, pipelines are known which have a multilayer cross-sectional structure. Due to the different layers, the pipes can be matched in their properties to the respective requirement profile.

So is out of the DE 100 18 324 C2 a pipe made of plastic, in which an inner layer is provided which is equipped with special additives for the protection of polymer chains of the plastic of the pipes. In particular, the additives protect the polymer chains from the influence of aggressive media. In an intermediate layer of the construction, glass fibers, glass spheres or glass powder are incorporated as fillers in this pipeline in order to reduce or completely avoid immigration of the additives from the inner layer. As plastic for the production of the pipeline here polypropylene is used.

Water pressure pipes for the passage of, for example, cold water usually require no multilayer structure or an intermediate layer to protect against harsh chemicals. For water pressure pipes are therefore regularly used single-layer pipes made of plastic. Further, it is known to form these pipes of polyethylene with a wall thickness which withstands at least a pressure of 16 bar at 20 ° C. A use of fillers is not provided here, since they reduce the stability of the pipeline and thus would require a higher wall thickness. Furthermore, such pipelines may also have a cover layer of polypropylene or a special polyethylene for external protection of the pipeline. Polyethylene single-layer pipes are standardized with DIN8074, DIN8075 and EN12201, among others.

A training of pipeline networks by means of such pipes is done regularly by welding the pipes with each other or by means of fittings or fittings. Essential in welding is that the respective pipes and fittings are welded to surfaces that contain no fillers and are made of similar plastic materials in order to achieve the best possible welding result with a durable and tight connection of the welding partners. For pipelines with a cover layer, it is therefore necessary to first peel them consuming, so that the pipeline can be welded with, for example, an electrically heatable sleeve.

Furthermore, it is disadvantageous that in the case of a construction of a pipeline network due to an expansion coefficient of the plastic material used, a thermal expansion or a heat shrinkage of a longer pipeline has to be taken into account. A change in temperature and thus a change in length of the pipe can be done by heating the pipe due to the flowing medium or from outside the pipeline. For longer pipelines therefore constructive measures, such as bends or projections in the pipeline, provided to allow a change in length of the pipe so that the pipeline is not damaged or deformed in an undesirable manner. However, the bends or Versprünge must also be formed by welding pipe sections with fittings in the pipeline or the pipeline network, which has an increased workload to form a pipeline network result.

It is therefore an object of the invention to provide a pipeline, a pipeline network and a method for producing a pipeline through which or a pipeline network can be made simpler and less expensive.

This object is achieved by a pipeline having the features of claim 1, a pipeline network having the features of claim 13 and a method having the features of claim 14.

In the plastic piping of the present invention having a three-layer cross-sectional structure, the structure has at least an outer layer, an inner layer and an intermediate middle layer, the middle layer containing fibers, the plastic of the outer layer, the inner layer and the middle layer being polyethylene (PE).

The use of polyethylene to form the pipeline makes it possible to make the pipeline much more resistant than, for example, a pipeline Polypropylene, as the polyethylene is relatively impact resistant. The pipeline made of polyethylene can therefore also be used in civil engineering for underground installation. It also makes it possible in the first place to form the middle layer with fibers as a filler, since the fibers, in particular extrudable short cut fibers, reduce the pressure resistance of the pipes, which can be compensated for by the use of the polyethylene. By incorporating the fibers in the middle layer, it is possible to utilize the outer layer and / or the inner layer to connect the tubing to another tubing or fitting by welding. The outer layer, the inner layer and the middle layer are load-bearing layers which noticeably influence the strength of the pipeline.

Since the outer layer is made of polyethylene, can be completely dispensed peeling the outer layer for welding the pipe with a fitting.

Since the fibers in the manner of a wick by capillary action can promote a diffusion of media, it is also advantageous that the fibers are surrounded in the middle layer of the outer layer and the inner layer. Although the fibers in principle reduce the pressure resistance of the pipelines compared to pure polyethylene, it has surprisingly been found that a thermal expansion coefficient of the piping through the fibers is substantially improved. That is, a thermal expansion or contraction due to a temperature change of the pipe is comparatively lower than that of a pure polyethylene pipe. This makes it possible to dispense with a formation of pipe networks to a formation of bends or jumps within a pipe as far as possible, since the taking place at a temperature change change in length of the pipe is tolerable small. However, it is possible to design and use the pipe according to EN12201, DIN8074 and DIN8075 in the version valid prior to the priority date of the present application. Overall, piping networks can be made simpler and thus more cost-effective with such a pipeline.

It is particularly advantageous if only the middle layer contains fibers. Thus, a particularly good weldability of the pipeline with, for example, fittings or any other coupling elements for the formation of a pipeline network is guaranteed. The same applies to a butt welding two pipe ends, since then the middle layer can also be completely closed against an environment and absorbed between the outer layer and the inner layer.

Further, the polyethylene (PE) of the outer layer and / or the inner layer may be free of fillers. The outer layer and / or the inner layer can therefore consist of pure polyethylene. In particular, an outer layer of pure polyethylene ensures a particularly good weldability. The fibers may be short fibers of up to 6 mm, preferably up to 4 mm in length. Fibers of this length are still well extrudable and can be easily added to the polyethylene. The fibers can reduce a pipe length change compared to a polyethylene non-fiberized pipe by up to 70%, at least up to 50%.

The fibers may be stone fibers, glass fibers or carbon fibers. It can also be provided that the fibers are impregnated with an adhesion promoter, a so-called size. In principle, all types of fibers can be added to reduce a change in length due to temperature of the middle layer.

Advantageously, a fiber content of the middle layer 5 to 20 wt .-%, preferably 16 to 20 wt .-% amount. The middle layer is then still formed as a load-bearing layer with respect to a compressive strength. An increase in fiber content, however, can not significantly affect a change in length due to temperature, but reduce a pressure resistance of the pipeline.

It is particularly advantageous if the fibers are arranged in the axial direction of the pipeline. The fibers are then oriented substantially in the direction of a longitudinal axis of the pipeline. This fiber orientation can be achieved by extruding the polyethylene of the middle layer together with the fibers. As a result of the extrusion, the fibers then align substantially in the axial direction of the pipeline. Since the fibers are then no longer radially relative to the axial direction of the pipeline, the fibers can not improve the pressure resistance of the pipeline. The axial orientation of the fibers, on the other hand, may favor a decreasing length expansion or length contraction.

A layer thickness of the outer layer, the inner layer and the middle layer may be formed coincident. In principle, however, it is also possible that the outer layer, the inner layer and the middle layer each have different layer thicknesses.

The polyethylene (PE) of the outer layer, the inner layer and / or the middle layer can be a low density polyethylene (LDPE), middle density polyethylene (MDPE), high density polyethylene (HDPE), cross-linked polyethylene (PE-X) or raised temperature polyethylene (PE-RT). Depending on the requirements of the pipeline, the pipeline can then be formed from a suitably suitable material. In this case, the outer layer, the inner layer and the middle layer, which is surrounded by the outer layer and the inner layer, may be formed from different versions of polyethylene. For example, a pipeline for use in a district heating network may be thermally stable with the inner layer and scratch-resistant with the outer layer for underground installation.

In addition, the structure may comprise an intermediate layer which forms a barrier layer. The barrier layer can effectively prevent a passage of, for example, oxygen or pollutants through a wall of the pipeline from or into the medium to be transported.

The plastic of the intermediate layer may be polyamide (PA) or an ethylene-vinyl alcohol copolymer (EVAL, EVOH).

The pipeline may be a pressure pipeline capable of up to a pressure of up to 10 bar, preferably 16 bar, especially preferred 20 bar is formed at 20 ° C. Under a penstock is a pipe understood that can withstand an overpressure of at least 0.5 bar. Furthermore, the pipeline may have an outer diameter of up to 500 mm.

The pipeline network according to the invention comprises a pipeline according to the invention and a fitting made of polyethylene (PE) connected to the pipeline, the fitting being welded to the pipeline. The fitting may for example be a fitting which is made of pure polyethylene and has a monolayer structure in cross-section. Since fittings are relatively short compared to pipelines or have a much smaller length, a possible change in length of the fitting is not important, which is why the fitting may be formed free of fibers. Further advantageous embodiments of a pipeline network result from the feature descriptions of the device claim 1 back-related dependent claims.

In the inventive method for producing a plastic pipe with a cross-sectional three-layer structure, the structure has at least an outer layer, an inner layer and an intermediate, fiber-containing middle layer, wherein the outer layer, the inner layer and the middle layer by means of coextrusion of polyethylene (PE ) be formed. With regard to the advantages of the method according to the invention, reference is made to the description of advantages of the pipeline according to the invention. Further advantageous embodiments of the method will become apparent from the feature descriptions of the device claim 1 related subclaims.

The invention will be explained in more detail with reference to the accompanying drawings.

The figure shows a schematic representation of a pipeline 10 in a cross-sectional view. The pipeline 10 is made of plastic and has a three-layer structure 11 their wall 12 on. The structure 11 includes an outer layer 13 , an inner layer 14 and a middle class 15 , The plastic of the outer layer 13 , the inner layer 14 and the middle class 15 is polyethylene (PE), the middle layer 15 Contains fibers. The polyethylene of the outer layer 13 and the inner layer 14 is, however, free of fillers.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10018324 C2 [0003]

Claims (14)

A plastic tubing (10) having a cross-sectional three-layered structure (11), said structure comprising at least one outer layer (13), inner layer (14) and intermediate middle layer (15), said middle layer containing fibers, characterized in that the plastic of the outer layer, the inner layer and the middle layer is polyethylene (PE). Pipe after Claim 1 , characterized in that only the middle layer (15) contains fibers. Pipe after Claim 1 or 2 , characterized in that the polyethylene (PE) of the outer layer (13) and / or the inner layer (14) is free of fillers. Pipe according to one of the preceding claims, characterized in that the fibers are short fibers of up to 6 mm, preferably up to 4 mm in length. Pipe according to one of the preceding claims, characterized in that the fibers are stone fibers, glass fibers or carbon fibers. Pipe according to one of the preceding claims, characterized in that a fiber content of the middle layer (15) is 5 to 20 weight percent, preferably 16 to 20 weight percent. Pipe according to one of the preceding claims, characterized in that the fibers are arranged in the axial direction of the pipe (10). Pipe according to one of the preceding claims, characterized in that a layer thickness of the outer layer (13), the inner layer (14) and the middle layer (15) is coincident. Pipe according to one of the preceding claims, characterized in that the polyethylene (PE) of the outer layer (13), the inner layer (14) and / or the middle layer (15) comprises a low density polyethylene (LDPE), middle density polyethylene (MDPE), high density polyethylene (HDPE), cross-linked polyethylene (PE-X) or raised temperature polyethylene (PE-RT). Pipe according to one of the preceding claims, characterized in that the structure (11) has an intermediate layer which forms a barrier layer. Pipe after Claim 10 , characterized in that the plastic of the intermediate layer is polyamide (PA) or an ethylene-vinyl alcohol copolymer (EVAL, EVOH). Pipe according to one of the preceding claims, characterized in that the pipe (10) is a pressure pipe, designed for a pressure of up to 10 bar, preferably 16 bar, more preferably 20 bar at 20 ° C. A pipeline network comprising a pipeline (10) according to any one of the preceding claims and a polyethylene (PE) fitting connected to the pipeline, the molding being welded to the pipeline. Method for producing a plastic pipe (10) having a cross-sectionally three-layer structure (11), the construction comprising at least one outer layer (13), an inner layer (14) and an intermediate, fiber-containing middle layer (15), characterized in that the outer layer, the inner layer and the middle layer are formed by coextrusion of polyethylene (PE).

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