EP2613326A1 - Power and/or telecommunications cable capable of preventing the spread of a fire - Google Patents

Abstract

The cable (1) has an elongated electrically conducting element (2), and a thermal protection layer (3) that coaxially surrounds the electrically conducting element, where the protection layer incudes glass fibers with a density of 0.5 g per cubic cm. The protection layer includes a glass fiber ribbon, and has a surface mass of 120 to 160 g per square meter. The protection layer has a thickness of about 0.10 mm to 0.40 mm. An optional layer (4) is allowed to surround the protection layer. The protection layer is in direct physical contact with the conducting element. The conducting element is of monobrin type or multistranded type element.

Description

The present invention relates to an aluminum-based cable adapted to withstand extreme thermal conditions, and more particularly adapted to prevent the spread of a fire.

The invention finds a particularly advantageous, but not exclusive, application in the field of energy and / or telecommunication cables, which are intended to remain operational for a defined time when they are subjected to high heat and / or directly to flames.

Today, one of the major challenges of the cable industry is the improvement of the behavior and performance of cables in extreme thermal conditions, especially those encountered during a fire. For reasons of safety, it is indeed essential to maximize the capabilities of the cable to delay the spread of fire on the one hand, and resist fire on the other hand. A significant slowdown in the progression of the flames, it is as much time gained to evacuate the places and / or to implement appropriate means of extinction. Better fire resistance gives the cable the ability to operate longer, with less degradation.

Whether electrical or optical, intended for energy transmission or data transmission, a cable is schematically constituted by at least one conductive element extending inside at least one insulating element. It should be noted that at least one of the insulating elements may also act as protection means and / or that the cable may further comprise at least one specific protective element forming a sheath.

In particular, a cable having an aluminum conductive element and which is installed near a flammable material must be able to withstand fire temperatures ranging from 750 ° C to 900 ° C not to be a fire spreader. However, these fire temperatures are higher than the melting temperature of aluminum which is of the order of 658 ° C.

However, it is known that among the best insulation and / or protection materials used in the cable, many of them are unfortunately also excellent flammable materials. This is particularly the case of polyolefins and their copolymers, such as for example polyethylene, polypropylene, copolymers of ethylene and vinyl acetate, copolymers of ethylene and propylene. However, in practice, this excessive flammability is totally incompatible with the fire resistance requirements mentioned above.

In the field of cabling, there are many methods to improve the fire behavior of the polymers used as insulation and / or cladding materials.

The most widespread solution to date has been the use of halogenated compounds, in the form of a halogenated by-product dispersed in a polymer matrix, or directly in the form of a halogenated polymer, as in the case of a polyvinyl chloride. vinyl (PVC) for example. However, current regulations now tend to prohibit the use of such substances mainly because of their potential toxicity and corrosivity, whether at the time of manufacture of the material, or during its decomposition by fire. This is all the more true as the decomposition in question can intervene accidentally during a fire, but also voluntarily during an incineration. In any case, the recycling of halogenated materials is still particularly problematic.

This is why we use more and more non halogenated flame retardants, including metal hydroxides such as aluminum hydroxide or magnesium hydroxide. This type of technical solution, however, has the disadvantage of requiring large amounts of charges to achieve a satisfactory level of efficiency, both in terms of ability to delay the spread of fire, as fire resistance. For example, the content of metal hydroxides can typically reach 150 to 200% by weight relative to the total amount of resin. However any massive incorporation of charges induces a considerable increase in the viscosity of the material, and consequently a significant decrease in the extrusion rate, resulting in a significant drop in productivity. The addition of too large amounts of fire retardant additives is also causing a significant deterioration of the mechanical and electrical properties of the cable.

The document GB 2,035,666 describes, in its prior art, a cable capable of operating at high temperatures comprising at least one conductor of aluminum or copper, coated longitudinally or helically with a mineral insulating layer based on glass fibers. It is stated that this material is difficult to handle and that the manufacturing process is thus tedious and time consuming. On the other hand, it is stated in this document that the glass fiber layer exhibits instability of behavior at temperatures of the order of 400-500 ° C., and that at about 700-800 ° C. , fiberglass has a viscous phase, making it less insulating.

Thus, the object of the present invention is to overcome the drawbacks of the prior art by proposing a fire-resistant power and / or telecommunication cable, said cable also making it possible to avoid the problems of the state of the in particular by providing significantly improved mechanical properties, while having a service feature during a fire.

• au moins un élément électriquement conducteur allongé, et
• une première couche de protection thermique entourant coaxialement ledit élément électriquement conducteur,

caractérisé en ce que la première couche de protection thermique comprend des fibres de verre, d'une masse volumique d'au moins 0,5 g/cm³.The present invention relates to an energy and / or telecommunication cable comprising:

• at least one elongated electrically conductive element, and
• a first thermal protection layer coaxially surrounding said electrically conductive element,

characterized in that the first thermal protection layer comprises glass fibers having a density of at least 0.5 g / cm ³ .

It has been demonstrated that such a fiberglass layer makes it possible to render the cable resistant to fire by limiting the propagation of a fire by it to the surrounding objects (curtains, etc.), while ensuring a functionality of service. Indeed, the first layer of thermal protection prevents the electrically conductive element from melting, especially when it is aluminum. Thus, the thermal barrier formed by the fiberglass layer will prevent melting of said electrically conductive member and, therefore, also prevent the ignition of surrounding materials that may result from molten aluminum droplets while allowing the cable to operate despite the fire.

The first fiberglass layer thus makes it possible to resist fire better than the fiberglass layer described in the document GB 2,035,666 .

In a preferred embodiment, the first layer may comprise at least one glass fiber ribbon. Said ribbon notably helically surrounds the electrically conductive element.

The fiberglass ribbon can cover the electrically conductive element with a recovery rate of the order of 15% - 20%.

The first layer of the invention may have a density of at least 0.8 g / cm ³ , and preferably at least 1 g / cm ³ .

The first layer may have a density of at most 2 g / cm ³ , and preferably at most 1.5 g / cm ³ .

In a particularly preferred manner, the first layer may have a density ranging from 1.0 to 1.5 g / cm ³ .

The first layer of the invention can be advantageously used as a thermal barrier, in particular against flames. It makes it possible to maintain the integrity of the electrically conductive element for a temperature of at least 800 ° C., and preferably at least 1000 ° C. It thus avoids the fusion of the electrically conductive element during a fire. Advantageously, the first layer of the invention may have a thermal conductivity of at most 0.25 W / m ° C (watt per meter-degree Celsius).

Preferably, the thickness of the first layer varies from 0.10 mm to 0.40 mm. For example, if the first layer comprises only a ribbon of fiberglass, the thickness will be of the order of 0.10 mm and if it comprises two, the thickness will be of the order of 0.40 mm.

Preferably, the first layer (fiberglass) has a basis weight of between 120 and 160 g / m ² .

The electrically conductive element of the invention may be a material chosen from aluminum (Al) or an aluminum alloy. The aluminum alloy may be selected from copper aluminum, nickel aluminum, and copper and nickel-plated aluminum, or a combination thereof.

The electrically conductive element may for example be of the single-strand or multi-strand type.

Advantageously, the cable of the invention may comprise a second layer surrounding said first layer. This second layer may be formed by extrusion or taping according to techniques known to those skilled in the art so as to be composed of one or more sub-layers, such as preferably two.

Preferably, the second layer is electrically insulating and may be of a material chosen from a synthetic rubber, such as, for example, silicone rubber, and a polyolefin, such as, for example, ethylene-vinyl acetate ethylene copolymers. (EVA), or one of their combinations.

Advantageously, the thickness of the second layer varies from 0.5 mm to 3.0 mm.

When the cable of the invention comprises said second layer, the first layer can be directly in physical contact with the electrically conductive element, and said second layer can be directly in physical contact with the first layer. The cable may also include a protective sheath surrounding the second layer.

In a particularly preferred embodiment, the power and / or telecommunication cable is an insulated electrical conductor in which the elongated electrically conductive member is a central member.

The present invention also relates to the use of a cable as described above to limit the spread of a fire.

For a better understanding of the invention, the description will refer to an accompanying drawing and which is only illustrative and not limiting.

• La figure 1 illustre une vue en perspective et partiellement en coupe d'un câble d'énergie selon un mode de réalisation préféré de l'invention.

On this drawing :

• The figure 1 illustrates a perspective view and partially in section of an energy cable according to a preferred embodiment of the invention.

Examples of realization: Example 1: Example of Composition of a Cable According to the Invention Figure 1)

For the sake of clarity, only the essential elements for understanding the invention have been shown schematically, and this without respect of the scale on the figure 1 .

The energy cable 1, shown on the figure 1 , is an insulated electrical conductor comprising a central conductor element 2, in particular of aluminum, of multi-strand type, and, successively and coaxially around this element, a first layer 3 formed of a fiberglass strip (strip) marketed by the company STEVTISS or TISSTECH, or a fiberglass ribbon marketed by SCAPA under the reference SFR10 / 103.

This tape covers the conductive element with a recovery rate of the order of 15% - 20% so as to ensure that the entire surface of the conductive element is protected from flames. Above this fiberglass ribbon is deposited a second layer 4 consisting of two sublayers of an extruded material based on silicone rubber: a layer of white color material referenced El 111 polysiloxane polymer and a layer black material referenced EM107 in ethylene copolymer in the European standard for rolling stock EN 50382-1. This second layer 4 is an optional layer.

In this example, the thickness of the tape (ie first layer 3) is 0.12 mm and its density is 1.16 g / cm ³ . The thickness of the second layer 4 is of the order of 2.7 mm.

Example 2: Process for producing a cable according to the invention

Said multi-stranded aluminum electrical conductor is surrounded by a first layer of fiberglass ribbon as mentioned in Example 1. This fiberglass ribbon is then extrusion-coated with the above-mentioned two silicone and polyolefin rubber layers. .

Tape and extrusion techniques are well known to those skilled in the art and will not be further explained in the present application.

Experimental test

The cable as described in Example 1 was subjected to a fire test. A torch projecting a flame of 850 ° C has indeed been positioned near the cable according to the invention for 1h so that the flame touches a portion of the cable. A sheet of paper was also placed near the cable, about 30 cm away from the flame of the torch.

It turned out that after one hour, the second layer of silicone rubber and polyolefin ignited and burned completely in the area in contact with the flame, but that the multi-stranded aluminum conductor was remained intact thanks to the fiberglass ribbon. Besides, this one too was intact. Moreover, the paper sheet placed at 30 cm from the cable did not ignite, thus showing that the cable according to the invention is not a fire propagator.

Although the invention has been described in connection with a particular embodiment, it is obvious that it is not limited thereto and that it comprises all the technical equivalents of the means described and their combinations if they are within the scope of the invention.

Claims (11)

Energy and / or telecommunication cable (1) comprising: at least one elongated electrically conductive element (2), and a first thermal protection layer (3) coaxially surrounding said electrically conductive element (2),
characterized in that the first thermal protection layer (3) comprises glass fibers having a density of at least 0.5 g / cm ³ . Cable (1) according to claim 1, characterized in that the first layer comprises at least one glass fiber ribbon. Cable (1) according to claim 1 or 2, characterized in that the first layer has a density of at least 0.8 g / cm ³ , and preferably at least 1 g / cm ³ . Cable (1) according to one of the preceding claims, characterized in that the first layer has a density of at most 2 g / cm ³ , and preferably at most 1.5 g / cm ³ . Cable (1) according to one of the preceding claims, characterized in that the first layer (3) has a weight per unit area of the order of 120 to 160 g / m ² . Cable (1) according to one of the preceding claims, characterized in that the thickness of the first layer (3) is of the order of 0.10 mm to 0.40 mm. Cable (1) according to one of the preceding claims, wherein the electrically conductive element (2) is made of material selected from aluminum (Al) or an aluminum alloy. Cable (1) according to one of the preceding claims, characterized in that it comprises a second layer surrounding said first layer. Cable (1) according to claim 8, characterized in that the second layer is of a material selected from a synthetic rubber, and a polyolefin, or a combination thereof. Cable (1) according to one of the preceding claims, characterized in that the first layer (3) is in direct physical contact with the electrically conductive element (2). Cable (1) according to one of the preceding claims, characterized in that it is an insulated electrical conductor in which the electrically conductive element (2) is a central element.

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