DE4009101A1 - Non-electrically tracking compsn. as outer jacket for cable - comprising highly-filled polyolefin of high softening pt. contg. small proportion of metal hydroxide - Google Patents

Abstract

Compsns. (I), which are non-self extinguishing, contain (A) large proportion of polyolefin with high softening pt. (B) large proportion of filler, and (C) small proportion of metal hydroxide. Pref. (A) is high density polyethylene or is polypropylene. (B) is chalk. (C) comprises at most 20%, esp. about 16%. (I) comprises 16-25% (A); 3-8% EVA, EEA, EBA; 45-64% chalk; 10-20% metal hyroxide; 1.6-3.2% C black concentrate (50 kg, sic); and 0.15-1.0% anti-ageing agent(s). Partic. (I) comprises 19.2% HPDE (sic, HDPE, high density polyethylene), 6.4% EVA VAC max. 40%), 6.4% EPDM, 16% Mg(OH)2, 48.1% chalk, 0.7% antiageing agent, and 3.2% C black concentrate (50%). USE/ADVANTAGE - In electric fields of high field strength, e.g., where overhead lines and cables are led together, partic. (claimed) as outer jacket for optical air cables. (I) contain only small proportion of (C) and so are not self-extinguishing but have good nontracking properties, are readily processed, have good shape-stability on mechanical loading, and are shape-stable at up to 60 deg.C.

Description

The invention relates to a leakage current-proof Plastic mixture for use in electrical fields high field strength, especially as an outer jacket for Optical aerial cables for high-voltage lines with one Mixture of metal hydroxides.

Such leakage-proof thermoplastic mixtures are used where there are high field strengths for the destruction of not specially equipped Plastics. High field strengths occur e.g. B. in Area of substations where overhead lines and cables be merged, and between the phases of High-voltage overhead lines.

Are dielectric optical cables on High-voltage overhead lines installed, so the jacket be equipped to be leakproof.

DE 35 04 041 A1 is more optical for the jacket Through a self-extinguishing plastic mixture described the addition of 30-60% metal hydroxide. At the Attack of high field strengths on this self-extinguishing Material is a highly insulating leakage current resistant Residue on the surface of the jacket. However, there are "self-extinguishing" mixtures with a high  Metal hydroxide content in the melt very viscous and difficult to work with. Mixtures also tend of PE / EVA copolymer and ethylene / propylene copolymer with high proportion of metal hydroxide in mechanical Exposure to the cold river. Your mechanical strength is very bad at temperatures above 50 ° C. There hot summer days temperatures up to 60 ° C Cable sheaths can occur is the use of these plastic mixtures problematic.

In avoiding the disadvantages described, the present invention the task of a Plastic mixture of the type mentioned above train that it is easy to process a good one Has dimensional stability under mechanical stress and remains dimensionally stable even at temperatures up to 60 ° C.

To achieve this object, the invention provides that the Plastic mixture is not self-extinguishing that it a high proportion of a high polyolefin Softening point and contains a lot of filler, in particular Chalk and only a small proportion of metal hydroxides. The metal hydroxide content should be limited to a maximum of 20% be.

The polyolefin can be particularly advantageous with high Softening point a high density polyethylene (HDPE) or be a propylene (PP).

Despite the substantial reduction in the share of Metal hydroxides will be excellent Creep resistance achieved although this mixture preferably not about 16% metal hydroxides is self-extinguishing.

The advantages of high tracking resistance remain obtained with a composition of the plastic mixture

A is used as the preferred mixture Plastic composition

By adding a relatively high proportion of Chalk is used even with high electrical loads, especially with very strong electric fields get high tracking resistance, whereby by Reduction of the metal hydroxide proportions Material savings while improving the Processing is achieved.  

The proposed leakage-proof plastic mixtures are ideal for the production of the Outer sheath of optical air cables.

Claims (6)

1. Creep current-resistant plastic mixture for use in electrical fields of high field strength, in particular as an outer jacket of optical air cables for high-voltage lines with a mixture proportion of metal hydroxides, characterized in that it is not self-extinguishing, that it contains a high proportion of a polyolefin with a high softening point and a lot of filler , especially chalk and only a small amount of metal hydroxide. 2. Plastic mixture according to claim 1, characterized characterized in that the proportion of metal hydroxides is at most 20%, preferably about 16%. 3. Plastic mixture according to claim 1 or 2, characterized characterized in that the polyolefin with high Softening point a high density polyethylene (HDPE) or is a polypropylene (PP). 4. Plastic mixture according to one of claims 1 to 3, characterized in that the following mixture composition is used: 5. Plastic mixture according to claim 4, characterized in that the following mixture composition is used: 6. Plastic mixture after one or more Claims 1 to 5, characterized in that they is used as an outer jacket for optical air cables.