DE3229352C2 - Halogen-free, flame-retardant cable with functional integrity in the event of fire for a certain period of time - Google Patents

Description

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The invention relates to a cable in the preamble of claim 1 mentioned Art.

Solehe cables are mainly used in fire-endangered systems with a high concentration of people and property used if, in the event of a fire, no corrosive secondary damage, e.g. B. arise from halogens and it is necessary to maintain the functionality of cables for a certain period of time ("emergency running properties").

In DE-OS 28 47 810, for example, a flame-resistant electrical cable of the type mentioned above Art described, whose individual conductor insulated with a thermoplastic or elastomer from an asbestos extrusion are surrounded. The inner jacket also consists of an asbestos extrusion.

The processing of asbestos is now generally considered to be harmful to health, and efforts are made to use this material to be replaced by other materials.

From US-PS 34 25 865 or from DE-OS 30 07 341 cables or conductors without an inner jacket are known in which the conductor is provided with inorganic coatings by DE-OS 28 49 940 it is known that highly filled, in particular filled with metal hydroxide polymer mixtures for flame-retardant Cables are suitable. However, these known measures do not by themselves lead to the decisive one Improvement of a cable of the type mentioned at the beginning

The "emergency running properties" required of a cable in the event of fire are usually verified by a test in accordance with IEC 331. Here, a Funktionsfähifkeit required by at least three hours in a pattern at a flame exposure of 800 ⁰ C. However, this functionality test relates only to the insulating behavior of the cable to be tested, but not to the electrical transmission performance in the LF range, for example when making calls. In the event of a fire, perfect electrical transmission behavior in the LF range is at least as crucial and important as adequate insulation behavior.

The object of the invention is to create a halogen-free, flame-retardant cable that without fire in the event of a fire Use of asbestos has "emergency running properties" The cable should be exposed to a flame of 800 ° C remain fully functional for at least three hours (IEC test 331). In addition, the inventive Cables have very good transmission behavior in the LF range, even in the event of a fire.

This problem is solved by the characterizing features of claim 1 or of the claim 2. Advantageous further developments result from the subclaims.

The use of a conductor coating with thermal barrier properties is enhanced in the present invention Cable the dielectric strength under the action of flame. Using just one layer made of mica or fiberglass would be disadvantageous:

- A glass silk braid melts at approx. 800 ⁰ C; an "emergency running property" is therefore not guaranteed.

- A mica winding over the wire can lead to a deterioration in the electrical transmission behavior, as this is the case with the mica platelets used there is a risk that they can penetrate the core insulation.

It is crucial that the conductor coating consists of at least two different components. Flaking and pressing of mica flakes into the core insulation and thus deterioration of the electrical transmission behavior both in the LF range and in relation to the Isolation behavior is avoided. By using an inner jacket made from a flame retardant Polymer mixture of metal oxide hydrates and other fillers is even the use of conventional, non-flame-retardant core insulation materials possible, which have better electrical transmission properties guarantee.

The invention is explained in more detail below
The cable constructed according to the invention consists of the following components:

ladder

Conductor winding Core insulation Inner jacket

reinforcement

Outer jacket

For the thermal barrier coating the conductor has The following structure has proven to be advantageous.

a) Two layers of spiral-wound mica paper and a layer of glass silk braiding on top or wrapping.

Braiding is advantageous in the case of smaller cross-sections (for example 1.5 mm ² ), while infiltration is advantageous in the case of larger cross-sections

b) As an alternative to a), a coated glass fiber tape is also possible. The coating consists of a halogen-free, flame-retardant polymer. It is crucial that this coating has an oxygen index of at least 40 (preferably 50). When carried out in accordance with IEC 331 function test at flame exposure at about 800 ⁰ C even better insulation performance was achieved than be 'indicated under a) mica / glass fiber coating.

For the core insulation, except with VPfauch good results with mineral-filled cross-linked Polyolefins achieved. An EPR / VPE copolymer blend is preferred which is crosslinked by conventional methods.

A flame-retardant halogen-free polymer mixture with fillers and, in particular, is used for the inner jacket Metal oxide hydrates used, which is so highly filled that the oxygen index is at least 40 Materials that have an oxygen index of 50 are preferred.

The reinforcement is applied over the inner jacket. It preferably consists of a steel mesh If a non-metallic finish is desired, it is coated or uncoated Fiberglass braiding possible as reinforcement.

The outer sheath consists of a polymeric, halogen-free material. This material is said to be oil resistant and possibly waterproof.

Very good results were achieved with the halogen-free polymer mixture as described in the DE-OS 49 940 are known.

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Claims (5)

Patent claims: 1. Halogen-free, flame-retardant cable with functional integrity in the event of fire for a certain time, with at least one ladder, each of which is led by one insulating polymer layer and a heat-resistant layer made of inorganic material and surrounded are embedded in a heat-resistant filling layer forming an inner jacket, which is reinforced by a reinforcement is surrounded, over which a casing forming an outer jacket is applied, thereby characterized in that the heat-resistant layer surrounding the conductors is applied directly to the conductors is applied and consists of an initially wound layer of mica and a layer braided on it or wound layer made of fiberglass and that the inner jacket is made of a filler material, in particular metal oxide hydrates filled polyirene mixture 2. Halogen-free, flame-retardant cable with functional integrity in the event of fire for a certain time, with at least one ladder, each of which is led by one insulating polymer layer and a heat-resistant layer made of inorganic material and surrounded are embedded in a heat-resistant filling layer forming an inner jacket, soft from a reinforcement is surrounded, over which a casing forming an outer jacket is applied, thereby characterized in that the heat-resistant layer surrounding the conductors is applied directly to the conductors and is made of a wound, coated with a halogen-free, flame-retardant polymer material There is glass silk tape, and that the inner jacket is made of one with fillers, in particular Metal oxide hydrates filled polymer mixture 3. Cable according to claim 2, characterized in that the polymer mixture of the coating one Has an oxygen index of at least 40 4. Cable according to one of claims 1 to 3, characterized in that the flame-retardant polymer mixture of the inner jacket made of a halogen-free, minerally highly filled material with a There is an oxygen index of at least 40. 5. Cable according to one of claims 1 to 4, characterized in that the glass fiber braid is coated with a halogen-free, flame-retardant polymer. 50