DE2934057C2 - Process for the production of electrical plastic-insulated cables - Google Patents

Description

The submission. Each invention relates to a method for Manufacture of electrical cables with one off networked thermoplastic or elastomeric: existing materials Isolation, in particular those which, after grafting on crosslinking agents, such as kites or their Compounds that can be crosslinked under the action of moisture, in which during a continuous run of the conductor, the insulation is extruded onto it as a concentric sheath.

The problem has long been known that thermoplastic Some plastics were only given a coating after a special surface treatment can (DE-AS 11 55 835). For this reason, small metal particles are used to produce conductive layers sprayed electrically onto the insulating material surface. Another option, a conductive one Applying a coating to the insulating surface of an electrical cable is the surface of the insulation with a flame to heat the hydrocarbon gas burns. In this case, the coal particles resulting from the combustion process are at least Superficially embedded in the insulation so that a conductive layer is formed.

However, these known measures are no longer suitable if the two partners are involved It is about insulating materials that are mechanically solid and also moisture-proof connected to one another Need to become. This shows, for example, that it is used as an insulating material for electrical cables in meshed or non-crosslinked versions Form of the polyethylene used Compared to the otherwise common insulating materials, such as polyvinyl chloride, lower adhesion forces to those used in connection technology, usually self-curing Plastics. The relatively low adhesive forces between today's z. B. Usual catfish In connection technology used polar casting resins based on polyurethane and the surface of a ml! one Polyethylene insulated cables are a question of the high interfacial tension between the two composite partners.

The invention is therefore based on the object of finding a way, even with from insulating Materials existing composite partners to achieve permanent superficial connections that mechanically are solid and moisture-proof, as is often the case with power distribution cables in particular

ίο connection and connection technology is required.

This object is achieved according to the invention in that the cable for activating the surface of the Insulation immediately after the shaping and laying of the insulating sleeve on the conductor by a

'.- ·, zone of intensified oxygen attack with simultaneous temperature increase to values substantially above the melting and extrusion temperature. This direct influence on the still untouched surface of the insulation leads to activation in the sense of a complete change in the surface affinity of the polymer material for the composite partner. The increased affinity after treatment, e.g. B. of polyethylene, the. Cable insulation to the filling compound used in the sleeve assembly, for example based on cast resin, does not decrease even if the connection remains subject to operation over a long period of time. It is essential that the insulating surface is influenced under strongly oxidizing conditions so that oxygen-containing groups can arise which lead to permanent polarization of the insulating surface. This effect cannot be achieved if the cable z. B. in Fs'.Ie a vapor-crosslinked insulation the vulcanization line or, as also already known (DE-OS 22 04 658), the cable has already passed through a salt bath, a liquid bath or a hot air line for the purpose of pressureless crosslinking of the insulation. In contrast to the Vuikanisierstrekken In the closed steam pipe (iCV system), however, the invention can also be used for the last-mentioned crosslinking sections if the Isoller surface is treated immediately after the extrusion in the liquid bath or before the hot air section in the sense of the invention.

According to the invention, the surface is activated by such a temperature increase that temperatures far above the melting or extrusion temperature of the respective insulating material. BeJ the Continuous cable production, this usually means that the cable emerging from the injection head of an extruder Isollerwerk'off immediately raised the temperature must become. In a continuation of the inventive concept, this can be done, for example, by Yass the surface of the insulation through those with excess oxygen the set flame of a burner is modified. With the help of such on the insulation Directional flame it is possible for a short-term substantial increase in temperature in the run to ensure critical near-surface areas. In this context one becomes that of the flame Set the generated temperature in areas of the insulation close to the surface so that the surface of the insulation after leaving the treatment zone, it still has a temperature of at least 250 ° to 350 ° '.

Another possibility, the activation of the surface To achieve the cable insulation is the one for one Corona discharge with simultaneous temperature increase of the surface during the continuous Ensure pass of the straight extrusion insulation.

This can happen, for example, that the wire is under high voltage when the conductor is connected to earth standing metallic pipe of a certain length passes through. If desired, this pipe can also be used Have supply options for oxygen.

In addition to the possibility of surface activation by corona discharges with a simultaneous increase in temperature of the insulation or by an impact on the insulation One can also continue to produce a directed flame set with excess oxygen of the inventive concept, the extruded insulation immediately after shaping a heat radiator, for example an infrared emitter, feeder ,, in its Inside through constant supply. Oxygen created a more oxidizing atmosphere ν J. is

The material that has been surface-treated in this way can be any polymer material, d a "r:> can be stretched by fillers. Au ^ h C «o ...- mere, for example of polyethylene, are g: '.st.

With the usual steam insulation on the basis of thermoplastic :. Plastics by means of so-called. CV systems, the extruded casing is practically inserted into the Vulkanisler tube, which is hermetically sealed to the outside extruded in. When leaving the pipe after 150 or 200 m length is a permanent activation the surface of the goods, as already stated, is no longer possible. For this reason, the invention dGrt can be used with advantage wherever free extrusion is possible. This is e.g. B. in use such materials are given where before the molding in the same operation or during a special upstream processing stage. Crosslinking aids are grafted onto the base molecules. These grafted connections, for example on the basis of Sllanen, then later form with presence of water the cross-linking bridges. Are in the production of such insulation according to the invention Proposed measures applied, then result due to the networked property of the Insulation, especially thermal, very resistant Cable, d 2 also at the branch or connection points be connected mechanically and moisture-tight with the usual joint filling compounds can.

The invention is described with reference to the figure 4> NEN procedure explained in more detail.

To manufacture z. B. a low-voltage cable with cross-linked insulation, the insulating material, for example a copolymer of ethylene, together with the cross-linking aids, is fed into the hopper 1 of the extruder><> 2. The material is mixed in this extruder, the crosslinking agents are distributed homogeneously and the silane or the silane compounds are grafted onto the base material. In this so-prepared state, the polymeric material is introduced into the extruder 4 through the connecting piece 3, which, when ΓΠαΓι apart from Ci ""! TTÖgUch ^ n Ent ° 3fl ⁱⁿ 2 ^'m I Ihprpahphprplrh, the shaping of the insulation on the conductor serves. In the extruder head 5 of the extruder 4, the conductor 6 is inserted and in the extruder head itself the insulating sleeve on 60 history

applied to the conductor. of the cable

In order to create a cable that meets the requirements for the production of branch or connection points in the sleeve area, a zone is immediately adjacent to the exit of the spray head. In the flame 7, indicated by means of shearling, the surface of the insulation, which is essentially at the spraying temperature, is increased to a multiple of the melting temperature of the respective insulation material. The increase in temperature must be accompanied by an increase in the oxygen content in the specified zone, so that the surrounding atmosphere has a stronger oxidizing effect. If, for example, the injection ^{temperature of the polymer is from 120 to 180 °} C., a surface temperature of the insulation of 250 to 350 ^° C. under the specified conditions has proven to be advantageous. The activation of the surface of the sprayed product can be achieved by higher temperatures and lower oxygen contents or by lower temperatures and higher oxygen contents.

If the core surface is activated in the manner according to the invention, the improvement in the adhesive strength compared to the casting resins used in the socket technology of 1 kV cables can be tested, for example, by using a casting resin body approx. 15 mm wide and approx. 100 mm long η the surface can harden. On the basis of ASTM D 90J-49, after curing, the force required to pull the insulating cover off the measuring resin is measured and pulled to a width of, for example, 1 mm. Table 1 shows typical values measured on cores from finished cables. The various specified thermal loads relate to the aging of the cable. The test specimens produced in each case are always produced using the same method as specified above. The “previous history of the cable” is understood to mean the corresponding pretreatment.

Table 1 Peel strength
inventive
proper vein (N ■ ram " ¹ )
normal
XLPE wire prehistory
of the cable 3.9 0.15 14 days room temperature 3.8 0.10 32 days room temperature 4.1 0.15 75 days room temperature 6.6 0.10 65 days 60 ° C 4.1 0.10-0.20 Heating cycle conductor 100 ° C 5.5 0.15-0.20 Heating cycle ladders 130 ° C

You can achieve even higher adhesive strengths on veins, if and especially with an excess of oxygen high surface temperature is used. It is advantageous that the vein quickly after the treatment is cooled (water bath), which avoids an adverse effect on the insulation as a dielectric will.

Table 2 shows the attainable values of cores and the influence of the short stringing at 70 or 135 "C:

Tabel

^{Peel strength (N · mm "1} ) cores according to the invention according to the invention, VPE cores

7 days room temperature 7.9 0.15 7 days 70 ⁰ C 8.2 0.15 7 days 135 ° C 8.5 0.10

1 sheet of drawings

Claims (3)

29 34 05 "Claims: 1. Process for the production of electrical cables with cores with cross-linked thermoplastic or elastomeric Materials of existing insulation, in particular those that, after grafting on crosslinking aids, how sitanes or their compounds can be crosslinked when exposed to moisture, wherein during a continuous pass of the conductor the insulation is concentric thereon Sheath is extruded on, characterized in that the cable for activating the surface the insulation immediately after the shaping and placing of the insulating cover on the conductor a zone with simultaneous temperature increase to values significantly above the melting and extrusion temperature is passed through. 2 The method according to claim 1, characterized in that that as a heat source for the activation while increasing the temperature of the surface of the Insulation the flame of a burner adjusted with excess oxygen is used. 3. The method according to claim 1, characterized in that the activation with simultaneous temperature increase the surface is carried out by corona discharge.