CH656090A5 - METHOD FOR PRODUCING A POLYETHYLENE COATING ON STEEL TUBES. - Google Patents

Description

The invention relates to a method for producing a polyethylene sheathing on steel pipes with a plurality of polyethylene marking strips distributed over the circumference on the surface of the polyethylene sheath, with simultaneous extrusion of a tubular film made of ethylene copolymer serving as a pressure sensitive adhesive and an overlying tubular polyethylene film using an extruder head with two ring channels the sheathing is formed, and on the surface of said marking strips are produced, and a device for carrying out the method.

Various methods are used to sign pipes, cables and lines from solid material rails for transferring earth faults. For example, simple labels with technical information 5 or advertising-effective images and trademarks, waterproof labels with the same texts or labeling tasks, texts with dyes (water-soluble or solvent-based) stenciled by an embossing process with color inlays, io longitudinal signatures generated by color spraying are used and it can also be extruded with a color in a different color than the base material.

Most of these methods do not result in weather-resistant signatures or fail when exposed to UV and Ternis temperatures with changing climatic conditions.

A plastic-coated object is only stable over a long period of time if it contains additional high UV stabilizers in the form of carbon black, acrylic ester additions or other UV-absorbing additions. '20 There are no known multiple, linear stripes that are permanent, UV and heat stable, as well as weather-resistant and which are produced in an extruded form by coloring a wide variety of types in a continuous process, provided that an underlying extruded adhesive also adheres to it to be encased and guaranteed to remain.

The invention has for its object to provide a method and an apparatus for performing the same, with which it is possible, during the extrusion 30 of the tubular pressure-sensitive adhesive and jacket film, to apply colored marking strips in the longitudinal direction to the jacket, which are intended for use in Make pipes laid in the ground recognizable in every position. The application should take place in such a way that the marking strips 35 are not pushed completely through the thermoplastic casing and that the physical and chemical properties of the casing are not impaired, e.g. through notch effects, change in elongation at break and chemical behavior, through UV-40 radiation or heat.

According to the invention, this object is achieved by the features specified in claims 1 and 6, respectively. Embodiments of the method result from claims 2 to 5.

45 In the case of the double pointed head used, an annular edge with outlet openings distributed over the circumference for the marking polyethylene is advantageously provided in the area of the ironing zone, i.e. in the upper third of the outer annular gap (from which the jacket film is extruded).

The shape of an extruded signature is limited in terms of width and depth in a casing, which is continuously pressed into the layer bearing the signature. A raised lenticular or flat design 55 of the signature can be achieved by an appropriate pressure difference control.

The shape can only be solved by preventing the in-depth penetration through the formation of the distribution channels.

60 It was also found that a marking polyethylene (hereinafter referred to as PE) in the i215 must be close to the coating PE to be signed. Namely

Jacket PE 0.4-0.5

Signing PE 0.6-0.9

65 During the extrusion process, the UV and heat stabilized dye must remain color-fast. This task becomes all the easier, the fewer admixtures (mixed polymer of the PE) are present. The possibility also arises

3rd

656 090

The marking threads are not only colored, but also heat- and UV-stabilized. These measures ensure that the strength properties, tensile strength, tensile strength and elongation at break are fully preserved and take into account the applicable DIN.

The versions can be supplemented by extruding a tracer thread in addition to the coloring, which perfectly identifies the identity of the plastic-coated object.

The PE selection of the marking PE to the sheath PE allows the processing and distribution of the marking PE-S without additional thermal insulation between the extruders, since the extrusion process can be carried out in a uniform temperature control.

The subject matter of the invention is explained below using an exemplary embodiment of the device for carrying out the method shown in the drawings.

Show it

1 shows a longitudinal section through the extruder head and the tube to be encased,

2 shows a longitudinal section through the front housing ring of the extruder head,

Fig. 3 shows a cross section according to A-B, and

Fig. 4 is a longitudinal section on an enlarged scale.

The extrusion head used for extruding two tubular films is known per se according to DE-PS 19 57 078 and consists of three housing rings. Here, a first housing ring 1 with a mandrel 2 is formed in one piece. Viewed in the working direction, an intermediate ring 3 axially adjoins the housing ring 1 and, with the conically tapering end section 4 of the mandrel 2, forms an annular gap 5 for the inner pressure-sensitive adhesive hose 19. Furthermore, between the intermediate ring 3 and

Ring channel 6 a baffle ring 7 fixed and interchangeable. While the housing ring 1 serves to apply the inner pressure-sensitive adhesive hose 19 emerging from the annular gap 5 to the pipe 17 to be encased and for this purpose is connected to the feed 8, a second housing ring 9 is arranged for the application of the outer polyethylene hose 18, which in Similar to the housing ring 1 and is closely connected to the side of the intermediate ring 3 facing away from it. The io annular gap 5 opens directly in front of the ring opening of a second annular gap 10, which is formed by the bevelled outer surface of the intermediate ring 3 and by the inner surface of the housing ring 9 parallel to this. The annular gap 10 is connected to an annular channel 11, 15 which is connected to a polyethylene feed 12 and whose cross section can be changed by means of a retaining ring 13, as in the case of the housing ring 1. The housing ring 1, the intermediate ring 3 and the housing ring 9 are connected to one another by screws 14. The heating of the Extru-2o derkopfes to the operating temperature is carried out with the adjustable heating elements 15.

A distributor ring 22 is arranged in the front housing wall 9 of the extruder head. This points in the area of the ironing zone, i.e. in the area of the upper third of the outer 25 annular gap 18 an annular channel 21 (see FIGS. 2 and 3). This ring channel 21 is connected to a channel 20 which passes through the front housing wall 9 and which is used to supply the signing PE. As can be seen from FIG. 3, the distributor ring 22 (in this example) 30 has four outlet openings 23 which are evenly spaced around the circumference and which open in the upper third of the annular gap (FIG. 4). This means that four marking strips are generated at the same time during extrusion and this ensures that at least one of the 35 strips is visible in each tube layer.

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3 sheets of drawings

Claims (6)

656090 PATENT CLAIMS 1. A process for producing a polyethylene sheathing on steel pipes with several circumferential marking strips made of polyethylene on the surface of the polyethylene jacket, with simultaneous extrusion of a tubular film made of ethylene copolymer serving as a pressure sensitive adhesive and an overlying tubular polyethylene film using an extruder head the ring is formed in two ring channels, and the above-mentioned marking strips are produced on the surface thereof, characterized in that a polyethylene with a melt index i2ii6 = 0.4 to 0.5 g / 10 min at 190 ° C. and for the outer jacket film the marking strips are a polyethylene mixed with a dye with the melt index i2, i6 = 0.6 to 0.9 g / 10 min at 190 ° C is used, and that the marking strips in a width of 8 mm and with a thickness of 50 to 100 microns are extruded simultaneously with the tubular film forming the jacket in the longitudinal direction of the tubes, being between the extrusion pressure for the jacket film and which maintains a pressure difference between 10 and 50 bar for the marking strips. 2. The method according to claim 1, characterized in that for a flush with the jacket surface of the marking strips they are extruded at a pressure of about 100 bar and the jacket film at a pressure of about 150 bar. 3. The method according to claim 1, characterized in that for the formation of a lenticular cross-sectional shape of the marking strips they are extruded with a pressure between 130 and 140 bar and the jacket film with a pressure of about 150 bar. 4. The method according to any one of claims 1 to 3, characterized in that a UV and heat-stabilized dye is added to the polyethylene for the marking strips. 5. The method according to any one of claims 1 to 3, characterized in that a phosphorescent dye is added to the polyethylene for the marking strips. 6. Device for performing the method according to one of claims 1 to 5, with an extruder head which has two concentrically arranged annular gaps, of which the outer is used for extruding the jacket film and the inner for extruding the pressure-sensitive adhesive film, characterized in that in the Front housing wall (9) of the extruder head, a distributor ring (22) is arranged, which has an annular channel (21) in the area of the upper third of the outer annular gap (18), which on the one hand serves to feed the signature polyethylene, through the front Housing wall (9) extending channel (20) is connected, and which on the other hand has at least three equally spaced outlet openings (23) which open into the upper third of the annular gap (18).