FI99158C - Method for protecting the surface of a plastic pipe for connection by electric welding and an electrically weldable plastic pipe - Google Patents

Description

99158

Method for protecting the surface of a plastic pipe for connection by electric welding and electroweldable plastic pipe 5 When handling, installing and connecting a plastic pipe, the surface of the pipe is very susceptible to damage. Among other things, modern methods of installing plastic pipes are based on drilling a tunnel for the pipe in the ground, which is then pushed through the tunnel, e.g. into a trench, which forms the next sealing point.

Needless to say, the pipe in such a treatment is scratched and soiled. This is detrimental, on the one hand, because the pipe material may be notch-sensitive, with scratches causing greater damage to the pipe during further processing, and on the other hand, because fouling of the pipes prevents welding from succeeding. Today, especially PE pipes are welded together by electro fusion socketing, the almost only cause of failure of which is a dirty or oxidized pipe surface.

20 For this reason, the pipe ends must always be cleaned, eg with sandpaper, before sealing. In practice, the cleaning result is often uneven (the underside of the pipe is treated the worst) and its quality depends on the professionalism of the performer.

The method of the present invention for coating plastic pipes and the plastic pipe coated by the method aim to eliminate the above-mentioned disadvantages so that, for example, an electric welder always has ready-to-install pipes to be welded without laborious preparations.

The method according to the invention is thus characterized in that a plastic surface is formed on the pipe. a layer with a suitable coating technique as a protective sheath, and • · · that the surface layer is formed at least at the ends of the pipe: easily removable to expose the connecting surface of the pipe required for electric welding.

: 35 In addition to the obvious advantages of pipe protection • 1 · · · 2 99158, the procedure according to the invention makes welding easier and also safer. Work safety and also the quality are affected by e.g. the fact that it is simply not possible to seal the pipes without removing the jacket 5 from the joints due to the larger than usual outer diameter. Thus, sealing with mechanical joints and / or welding must always be done with clean pipe ends, which ensures successful welding and the correct behavior of the machines.

Other preferred embodiments of the method according to the invention are characterized by what is stated in the claims below.

The electrically weldable plastic pipe according to the invention is characterized in that a plastic surface layer is formed on the pipe as a protective sheath so that the protective sheath can be easily removed at least at the ends of the pipe to expose the pipe connection surface required for electric welding.

In addition, the protective sheath provided in the tube according to the invention can prevent UV radiation from entering the surface layer of the tube itself to cause decomposition reactions.

. Today, plastic tubes are UV-stabilized by dyeing them with 'dyes containing heavy metals, often toxic * ·' ·· 'according to their intended use. In a tube with a sheath 25, this does not have to be done, but UV protection and the necessary coloring can only be achieved on the sheath at a much lower cost and with less environmental damage.

Other preferred embodiments of the pipe according to the invention are characterized by the following. claims.

The invention will now be described in more detail by way of example with reference to the accompanying drawings, in which Figure 1 shows an embodiment of the method 3 99158 according to the invention, Figure 2 shows another embodiment of the method according to the invention, Figure 3 shows a pipe according to the invention

Figure 1 shows the coating of a plastic pipe 2 with a surface layer by coextrusion according to the method according to the invention. The surface layer is formed of molten plastic 1 on a nominal-sized pipe 2 as a protective jacket 3. Ko-10 extrusion nozzles 5, e.g. cross-head nozzles are known to those skilled in the art and coextrusion per se will not be explained in more detail in this context. Included in the basic method or by separate means, which will be described later, the protective sheath is formed completely or at least at the ends of the tube 15 for easy removal. If desired, the protective casing must be removable by simple means, without the use of scratching or similar scratching tools, in order to keep the surfaces to be welded in the best possible condition. One of the removal mechanisms of the surface layer is known as the "peel-off" effect, which arises when the strength properties of the sheath are radial and axial. . are different.

• The surface layer 3 of the pipe 4 formed according to the invention, i.e. the protective sheath, can be formed e.g.

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• ‘25 ta LDPE or recycled waste plastic. The advantage of linear • ·: V LDPE compared to its price is its high scratch resistance- “**! and puncture resistance, on the other hand, the advantage of waste plastic is a particularly cheap price and synergy with the use according to the invention, which is very tolerant, e.g., of variations in the quality of the plastic. As the plastic material of the protective sheath, it is quite advantageous to use a material that is very poorly or not at all weldable, so that the protective sheath, which may not have been accidentally removed, reminds the person doing this at the latest at the welding stage.

When choosing a material, it is also possible to take into account the fact that if the protective sheath forming the surface layer of the pipe is formed of a plastic chemically different from the material of the pipe, the adhesion between the pipe and the protective layer is likely worse than if the materials are of the same material. In addition, the tendency of the adhesion between the tube and the protective jacket can be advantageously influenced by mixing a considerable amount of fillers in the protective jacket, or by running the protective jacket over the pipe at a relatively low temperature. By shaping the tool 10, the matter can be influenced, for example, in such a way that a so-called a cold seam from which the protective sheath easily tears. The purpose of both methods is to make the surface of the protective sheath to be formed relatively hard, i.e. low in adhesion, and its structure relatively rigid during coating, whereby it is easier to remove it from the pipe, e.g. by tapping. Suitable fillers are, for example, chalk and talc.

Referring now to Figure 2, which shows another embodiment of the method according to the invention 20, i.e. the coating of the plastic tube 6 with a surface layer 7 as a protective jacket. . with a gentle nozzle 8 by spiral rotation. At the same time, this coating method involves a "mechanical" method of removing the sheath, i.e. exposing the surface of the tube by disassembling the helically formed sheath by tearing off the end of the sheath (cf. Fig. 3).

In the case of coextrusion, a suitable helical tear joint can be obtained, e.g. water circulation. The coextrusion tool 5 can also be cooled locally so that a longitudinal tear joint is formed in the surface layer 3 35. The protective sheath can be

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= 99158 also forms a longitudinal tear rope or a thinner web of the tube, thus providing a seam that tears easily in the axial direction.

Thus, by means of the above-mentioned means, a so-called "Peel-off" effect, characterized in that the the strength properties of the layer are different in the radial and axial directions.

Preferred embodiments of the method according to the invention also include passing an anti-adhesive agent between the tube and the surface layer forming the protective sheath 10 during the coating step. At the same time, taking into account the intended use of the pipe to be formed, welding and / or crosslinking promoting agents can also be run between the pipe and the surface layer forming the protective sheath. Suitable welding aids are, for example, dicumyl peroxide. Crosslinking agents complement the crosslinking reactions of the pipe material at the joint surface and provide surface lubrication, which is also advantageous in terms of reducing the adhesion of the sheath. The crosslinking agents may be the same commonly known radicals used in the tube matrix material.

The above-mentioned substances which promote welding and / or cross-linking between the pipe and the protective sheath can be driven, for example, from a separate nozzle 9 in question.

25 in the form of a thin plastic film 10 containing substances, as shown in Fig. 2. Of course, this type of layer can also be formed by coextrusion.

....: Figure 3 shows schematically according to the invention. structure of the pipe 11. The surface layer, i.e. the protective sheath 30 12, is formed on the nominal size tube 13 so that the protective sheath is formed to be easily removable.

• · · ’· 1 1 The protective jacket made of linear LDPE or, for example, recycled waste plastic, is coated by coextrusion or by 35 tangential nozzles wound on a pipe. Sufficient fillers have been mixed into the sheath to provide a rigid structure, as well as color and UV stabilizers, so these substances are not needed at all in the pipe to be protected. Thus, according to a preferred embodiment of the invention, the tube itself is made of a natural, UV-stabilized plastic, while the protective sheath contains tube-identifying dyes and UV stabilizers.

In one embodiment, if the adhesion between the tube and the sheath cannot be adjusted to the desired area in the manufacturing process by other means, a thin plastic film containing an anti-adhesive is passed between the tube and the surface layer 14 forming the shield, which may also contain other desired, e.g. active ingredients to be incorporated between surfaces, such as welding and crosslinking agents.

The pipe according to the invention is used in such a way that the protective jacket 12 is peeled off from the ends 15 of the pipes to be welded together (cf. Fig. 3), the pipe ends are placed opposite each other and welding, e.g. electro fusion socketing, is carried out in a manner known per se. After this, the put-20 work is continued as normal and is not affected in any way by the protective jacket on the surface of the pipe.

It will be apparent to those skilled in the art that the various embodiments of the invention are not limited to the examples set forth above, but may vary from those set forth below; · Within the scope of 25 claims.

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Claims (26)

99158 A method for protecting the surface of a plastic pipe for connection by electric welding, characterized in that a plastic surface layer (3; 7; 12) is formed on the pipe (2; 6; 13) as a protective sheath by a suitable coating technique, and that the surface layer is formed at least at the pipe ends easily detachable to expose the connecting surface of the pipe required for electric welding. Method according to Claim 1, characterized in that the surface layer (3) is formed on the nominal-sized tube (2) as a protective sheath by coextrusion. Method according to Claim 2, characterized in that the coextrusion tool (5) is rotated so that a helical seam is formed in the surface layer (3). Method according to Claim 2, characterized in that the coextrusion tool (5) is cooled locally so that a longitudinal seam is formed in the surface layer (3). Method according to Claim 1, characterized in that the surface layer (7) is formed on the nominal length of the tube (6) as a protective jacket by spiral twisting by means of a tangential nozzle (8). j V Method according to one of Claims 1 to 5, characterized in that the protective jacket (3; 7; 12) forming the surface layer of the tube (2; 6; 13) is formed from linear LDPE. Method according to one of Claims 1 to 5, characterized in that the protective jacket (3; 7; 12) forming the surface layer of the pipe (2; 6; 13) is formed from recycled waste plastic. Method according to one of Claims 1 to 7, characterized in that the protective jacket (3 to 7; 12) forming the surface layer of the tube (2; 6; 13) is formed of a plastic chemically different from the material of the tube. Method according to one of Claims 1 to 8, characterized in that a considerable amount of fillers is mixed into the protective jacket (3; 7; 12) of the tube (2; 6; 13). Method according to one of Claims 1 to 9, characterized in that the protective jacket (3; 7; 12) is run on the pipe (2; 6; 13) at a relatively low temperature, in order to reduce its adhesion on the surface of the pipe. Method according to one of Claims 1 to 10, characterized in that an anti-adhesive is passed between the tube (2; 6; 13) and the protective jacket (3; 7; 12) during the coating step. Method according to one of Claims 1 to 11, characterized in that a substance which promotes the welding of the pipe is run between the pipe (2; 6; 13) and the protective sheath (3; 7; 12) during the coating step. Method according to one of Claims 1 to 12, characterized in that a material promoting the crosslinking of the pipe material is passed between the pipe (2; 6; 13) and the protective jacket (3; 7; 12) during the coating step. . * · ** · 25 Method according to one of Claims 9 to 13, characterized in that the substances j * to be inserted between the tube (2; 6; 13) and the protective sheath (3; 7; 12) (14); ': during the coating phase, run between the pipe and the protective jacket from a separate nozzle (9) thin substances containing substances; 30 in the form of a plastic film (10). • «« ... ^ 15. Electrically weldable plastic pipe, characterized in that a plastic surface layer (3; 7; 12) is formed on the pipe (2; 6; 13) as a protective sheath so that the protective sheath can be easily removed at least at the ends of the pipe to expose the joint surface of the pipe required for electric welding. Plastic pipe according to Claim 15, characterized in that the surface layer (3; 7; 12) is formed as a protective jacket on the nominal-sized pipe (2; 6; 13). Plastic pipe according to Claim 15 or 16, characterized in that the protective jacket forming the surface layer (3; 7; 12) of the pipe is made of linear LDPE. Plastic pipe 10 according to Claim 15 or 16, characterized in that the protective jacket forming the surface layer (3; 7; 12) of the pipe is recycled waste plastic. Plastic pipe according to one of Claims 15 to 18, characterized in that the protective jacket forming the surface layer (3; 7; 12) of the pipe consists of a plastic chemically different from the material of the pipe. Plastic pipe according to one of Claims 15 to 19, characterized in that a considerable amount of fillers is mixed with the protective jacket (3; 7; 12) of the pipe. Plastic pipe according to one of Claims 15 to 20, characterized in that the pipe (2; 6; 13). . and between the protective sheath (3; 7; 12) (14) there is an anti-adhesive agent. «I Plastic pipe 1 2 3 4 5 6 7 8 9 10 11 according to one of Claims 15 to 21, characterized in that between the pipe (2; 6; 13) 2 «« 1 and the protective jacket (3; 7; 12) (14 ) is a substance that promotes pipe welding. 4 s *: ': Plastic pipe 5 according to one of Claims 15 to 22, characterized in that a crosslinking agent for the pipe material is present between the pipe (2; 6; 13) 6 and the protective jacket (3; 7; 12). 8 «» « Plastic pipe 10 according to one of Claims 21 to 23, characterized in that between the pipe (2; 6; 13) and the protective jacket (3; 7; 12) there is a thin plastic film 11 (10) containing the desired, e.g. 99158 active ingredients to be incorporated between the surfaces. Plastic tube according to one of Claims 15 to 24, characterized in that the tube (2; 6; 13) is made of natural, UV-unstabilized plastic, while the protective jacket (3; 7; 12) contains tube identification dyes and UV stabilizers. . Plastic pipe according to one of Claims 15 to 25, characterized in that the strength properties of the protective sheath (3; 7; 12) are different in the radial and axial directions. t I I I. (• 1. •• M • · • I t I «• •» • t • · · «1 · • ·« t * 1 • «* ··« · · 99158