DD214240A1 - METHOD FOR PRODUCING POLYETHYLENE CABLES - Google Patents

Abstract

Process for the production of polyethylene cables with extruded conductive field-limiting layer. The inventive solution is intended to reduce the number of different field limiting materials. Depending on the task, the adhesive strength of the field-limiting layer is controlled by the polarity and the quantity added. According to the invention, a polymeric adhesion-reducing additive of approximately the same or lower melt viscosity but of higher polarity than the field-limiting layer is metered into a field-limiting material which fuses with the insulation and distributed homogeneously before or during the extrusion processing. The invention is limited to the cable industry.

Description

- Process for the production of polyethylene-Eabeln

Field of application of the invention

The invention relates to a process for the production of polyethylene cables with extruded conductive field-limiting layer.

Characteristic of the known technical solutions

Plastic or blast-insulated cables for voltages greater than 10 kV receive a conductive layer on the insulation for the purpose of field limitation.

This conductive field-limiting layer usually consists of conductive, melt-processable polymer blends. "These extruded layers are subject to various international requirements.

While in many cases a tightly-sealed with the insulation Fedlbegrenzungsschicht is preferred, other consumers prefer easily from the insulation Absiehbare layers.

With regard to the deductibility, international demands are also different.

, Thus, e.g. in the Swedish standard 424 14 17 for the peel force of 8-40 IT / cm. Ifech ÜS-Standard

"ASIC Sections 6-73, Section D, 1.3 require values of 1.8 to 8.2 kg for a 1.27 mm wide strip and the French Uorm HiT 33-S-23 (iTovember 1981) calls when

-Visual value an adhesion of 25 H / cm. For both heat-sealable and peelable field-limiting materials, a number of formulations are known which are suitable for either uncrosslinked, radiation crosslinked or peroxygenated.

_disch networked cables are suitable.

There are also known formulations which can be crosslinked or uncrosslinked (DB-OS 2 117 247, DE-OS 2 737 487, CH-PS 625 904).

The known recipes have the disadvantage that they are not universally applicable. They are therefore suitable either for welding or peelable Peldbegrenzungsschichten. The peelable Peldbegrenzungsniaterialien turn, depending on the requirements of the peel force usually suitable only for a particular application. The cable manufacturer is thus forced to store and process the different materials for all requirements coming into play »

Object of the invention

The solution according to the invention should make it possible to reduce the number of different field limiting materials required for meeting the different requirements of international regulations with regard to adhesive strength or peelability of the extruded Peldbegrenzungsschicht and thus to reduce the cost of storage and Tert conversion.

Explanation of the essence of the invention

The invention has for its object to find a method that allows to control the adhesion of the Peldbegrenzungsschicht on the polarity and on the metered amount.

The object is achieved according to the invention by adding to a strongly adhering or insulating with the insulation FeIdbegrenzungsmaterial, e.g. based on BEA or EVA with low VA content, before or during extrusion processing, a conductive polymeric Adhesive reducing additive of approximately equal or lower melt viscosity but higher polarity than the Peldbegrenzungsschicht is metered and homogeneously distributed, the adhesion of the extruded Peldbegrenzungsschicht of the metered amount the adhesion-reducing additive as well as the polarity is dependent.

As adhesion-reducing additive is preferably a conductive mixture

100 parts by weight of one with vinyl chloride (VG)

grafted ethylene vinyl acetate copolymers (SVA) having a vinyl acetate (VA) content of between 10 $ and 4OiS and a 7G content of between 10 $ and 60 $ 50 - 100 parts by weight conductive carbon black

and further additives, such as lubricants, stabilizers, crosslinking activators and possibly peroxides up to 20 wt .-%

Use. However, conductive mixtures of similar composition may also be based on other polar or strongly polar mono-, co- or terpolymers, such as PP, PVC, PUE, EVA, EEA, IiJBE, CSM, EPE, SPDB! etc. or their mixtures with each other as an adhesion-reducing additive use.

The addition of the additive is advantageously carried out in the form of granules via known dosing in the material hopper of the extruder or as a melt with the aid of an additional extruder into the melt of the field limiting material in the main extruder.

By using suitable screw constructions, e.g. With a special mixing part, a sufficient melt homogenization is achieved, which is the prerequisite for the removable field boundary layer can be removed without residue from the insulation.

The adhesion-reducing additive according to the invention can optionally be metered in both peroxide-containing and non-crosslinkable field-limiting materials which can be crosslinked by means of electron beams. When incorporating peroxides, the adhesion-reducing additive can also assume the function of a peroxide concentrate.

The method according to the invention makes it possible to change the adhesive strength of the field-limiting layer during ongoing production, and thus, e.g. To produce delivery lengths, the field boundary layer is removable only at desired locations, for example, at the beginning and at their

The application of the method is of course also in the W ise possible that the hitherto known as adhesion-reducing additive material is used as the starting material to which a non-polar or polar, conductive, strongly adhering or, with the insulation-welding material is added to increase the adhesion. The invention will be described in more detail using an exemplary embodiment.

embodiment

Sin conductive Peldbegrenzungsmaterial from a mixture of

100 parts by weight EVA with a VA content of 11 $ 67 parts by weight carbon black

0.6 part by weight of phenyl- β- I-ylththylamine is applied to a polyethylene layer in the OO extrusion process.

The conductive layer thus applied is not peelable from the polyethylene layer.

With the help of a dosing granules of a mixture ans

100 parts by weight of a $ 15 VO grafted EVA

with a VA share of $ 10 70. Parts by weight conductive carbon black 0.6 parts by weight phenyl- β- itaphthylamine

the o.g. Metered field limiting material. The extrusion takes place via the same extruder (25 Ό, I) = 32 mm). An adhesion of about 60 "H / cm is achieved with a mixing ratio of field-limiting material to an adhesion-reducing additive of 2: 1, and an adhesive strength of about 10 H / cm at a mixing ratio of 1: 1. In both cases, the conductive layer allowed no residue peel off the polyethylene layer.

Sufficient homogenization of the melt was achieved in this case by using a core-progressive screw with a 2/1-to-2-slompression ratio and easier screw cooling.

Claims (8)

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Erfindungsanspruchi 1. A process for the preparation of polyethylene cables with conductive field boundary layers, which have a desired defined adhesion to the insulation, characterized in that an insulating with the field boundary material before or during the extrusion processing, a conductive polyäurer adhesion-reducing additive of approximately equal or lower melt viscosity but higher polarity than the field boundary layer is added and distributed homogeneously. 2. The method according to item 1, characterized in that the adhesion-reducing additive is mixed in granulated form by means of dosing ^ before extrusion with the field limiting material and the Schmelzenhomo- genisierung by suitable screw constructions, z.3, with a special mixing part, achieved. 3. The method according to item 1, characterized in that the adhesion-reducing additive is added as a melt by means of an additional extruder of the melt of the welding field limiting material in the main extruder. 4. The method according to item 1 to 3, characterized in that a Z-jdosierung the adhesion-reducing additive only at desired times within the manufacturing process, e.g. to obtain a peelable field boundary layer at the beginning and at the end of a delivery length. - ο - 5. The method according to item 1 to 4, characterized in that an adhesion-reducing conductive mixture based on a vinyl chloride (VC) grafted Xthylenvinylacetat (EVA) copolymers having a vinyl acetate (VA) content between 1OfS and 40 $ and a VC content is added between IGi and 6OfJ. 6. The method according to item 1 to 4, characterized in that the adhesion-reducing additive, a conductive lischung on the basis of other polar mono-, co- or terpolymers, such as PP, PVC, PUH, EVA, EBA, MBE, GSM, SPH, EPOM, etc .. or their mixtures with each other is » 7. The method according to item 1 to 6, characterized in that the adhesion-reducing additives contain peroxides. 8. The method according to item 1 to 6, characterized in that the field-limiting layers are crosslinked by means of electron beams.