EP3404673B1 - Fire resisting cable - Google Patents

Description

The present invention relates to a cable comprising at least one elongated conductive element surrounded by at least two polymeric fire-resistant layers.

It typically, but not exclusively, applies to the field of fire-resistant safety cables, in particular halogen-free, capable of operating for a given period of time under fire conditions, without however being a fire propagator or significant smoke generator.

These safety cables are in particular energy transport cables or low frequency transmission cables, such as control or signaling cables.

One of the major challenges of the cable industry is improving the behavior and performance of cables under extreme thermal conditions, especially those encountered during a fire. For essentially safety reasons, it is indeed essential to maximize the cable's capacities to delay the propagation of flames on the one hand, and to resist fire on the other hand in order to ensure continuity of operation.

Significantly slowing the progression of the flames means that time is saved for evacuating the premises and / or for implementing appropriate extinguishing measures. In the event of a fire, the cable must be able to withstand the fire in order to function as long as possible and limit its degradation. A safety cable must also not be dangerous for its environment, that is to say not to give off toxic and / or opaque fumes when it is subjected to extreme thermal conditions.

Of the document EP-0 942 439 is known a fire resistant and halogen-free safety electric cable comprising a set of insulated electrical conductors, said set being surrounded by an external sheath. Each insulated electrical conductor is formed by an electrical conductor surrounded by an insulating layer obtained from a composition comprising a polymeric material and at least one ceramic-forming filler, said insulating layer thus being able to convert at least superficially into the state of ceramic at high temperatures corresponding to fire conditions. The polymeric material of this single insulating layer is chosen from a polysiloxane, an ethylene copolymer, and their mixture.

Of the document US2015 / 147571 a cable is known comprising an elongated conductive element surrounded by a first polymeric layer obtained from a first composition comprising a first polymeric material and a first filler, and a second polymeric layer obtained from a second composition comprising a second material polymer and a second charge.

However, it has been found that this safety cable of the prior art does not have optimal fire resistance properties, and remains relatively expensive when a polysiloxane is chosen as the insulating material.

The object of the present invention is to overcome the drawbacks of the techniques of the prior art by proposing in particular a cable having excellent fire resistance properties while limiting the risks of mechanical degradation of the electrical conductor or conductors which compose it, even at high temperature.

• une première couche polymérique obtenue à partir d'une première composition comprenant un premier matériau polymère et une première charge, et
• une deuxième couche polymérique obtenue à partir d'une deuxième composition comprenant un deuxième matériau polymère et une deuxième charge,

caractérisé en ce que :

• ladite première charge comprend au moins un premier oxyde de type oxyde d'un métal alcalino-terreux, et
• ladite deuxième charge comprend au moins un premier silicate et un deuxième silicate, le deuxième silicate étant différent du premier silicate.

The subject of the present invention is a cable comprising at least one elongated conductive element surrounded by at least:

• a first polymeric layer obtained from a first composition comprising a first polymeric material and a first filler, and
• a second polymeric layer obtained from a second composition comprising a second polymeric material and a second filler,

characterized in that:

• said first charge comprises at least a first oxide of the oxide type of an alkaline earth metal, and
• said second filler comprises at least a first silicate and a second silicate, the second silicate being different from the first silicate.

Thanks to the invention, the cable has very good fire resistance, and in particular makes it possible to significantly reduce or even avoid the formation of flaming droplets during combustion of the cable. Properties The mechanical properties of the cable of the invention are also improved, which allows it to continue to operate even at high temperatures.

• la norme NF C32-070 CR1 (2001),
• la norme DIN4102-12 avec les exigences de la performance E30, E60, E90, et
• la norme NBN 713020 Addendum 3 avec les exigences de la performance Rf60, Rf90 et Rf120.

The cable of the invention advantageously satisfies the conditions of the following standards:

• standard NF C32-070 CR1 (2001),
• DIN4102-12 with the performance requirements E30, E60, E90, and
• NBN 713020 Addendum 3 with the performance requirements Rf60, Rf90 and Rf120.

The invention as defined also has the advantage of being economical since it makes it possible to significantly limit or even avoid the use of polysiloxane in the insulating layer, while having very good resistance properties. fire.

1. The first polymer layer 1.1 The first charge

The oxide of an alkaline earth metal advantageously makes it possible to improve the electrical resistivity properties at high temperature of the first polymeric layer under the conditions of a fire.

Preferably, the oxide of an alkaline earth metal can be of high purity.

The term "high purity" means an oxide of an alkaline earth metal having a purity (by calcination) of at least 96.0%, preferably at least 98.0%, and in a particularly preferred manner at least 99.0%.

The oxide of a high purity alkaline earth metal advantageously limits the presence of electrically conductive compound (s), in particular in the form of impurity (s). The impurities may contain, for example, heavy metals. Preferably, the oxide of an alkaline earth metal can comprise at most 30 ppm of heavy metals, and preferably less than 10 ppm of heavy metals.

In a preferred embodiment, the oxide of an alkaline earth metal has a melting temperature of at least 1500 ° C, preferably at least 2000 ° C, and particularly preferably at least 2500 ° C.

As a preferred example, the first oxide of the first charge can be magnesium oxide (MgO).

The first charge can also comprise a second oxide different from the first oxide.

Preferably, the second oxide can be silicon dioxide (SiO ₂ ).

The first charge can comprise from 50 to 90% by weight of the first oxide relative to the total weight of the first charge.

The first charge can comprise from 10 to 30% by weight of the second oxide relative to the total weight of the first charge.

1.2 The first polymer material

The first polymer material of the invention comprises one or more polymer (s), the term polymer can be understood by any type of polymer well known to those skilled in the art such as homopolymer or copolymer (eg block copolymer, random copolymer, terpolymer, ..etc).

The polymer can be of the thermoplastic or elastomer type, and can be crosslinked by techniques well known to those skilled in the art.

In a particular embodiment, the first polymer material, or in other words the polymer matrix of the first composition, can comprise one or more olefin polymers, and preferably one or more ethylene polymers. An olefin polymer is conventionally a polymer obtained from at least one olefin monomer.

More particularly, the first polymer material can comprise more than 30% by weight of olefin polymer (s), preferably more than 50% by weight of olefin polymer (s), preferably more than 70% by weight of olefin polymer (s), and more preferably more than 90% by weight of olefin polymer (s), relative to the total weight of the first polymer material in the first composition. Preferably, the first polymer material is composed only of one or more olefin polymer (s).

By way of example, the first polymer material of the invention may comprise one or more olefin polymers, and preferably one or more ethylene polymer (s), chosen from a linear low density polyethylene (LLDPE); very low density polyethylene (VLDPE); low density polyethylene (LDPE); medium density polyethylene (MDPE); high density polyethylene (HDPE); an ethylene-propylene elastomeric copolymer (EPM); an ethylene propylene diene monomer terpolymer (EPDM); a copolymer of ethylene and vinyl ester such as a copolymer of ethylene and vinyl acetate (EVA); a copolymer of ethylene and acrylate such as a copolymer of ethylene and butyl acrylate (EBA) or a copolymer of ethylene and methyl acrylate (EMA); a copolymer of ethylene and alpha-olefin such as a copolymer of ethylene and octene (PEO) or a copolymer of ethylene and butene (PEB); and one of their mixtures. The preferred ethylene polymer is the copolymer of ethylene and octene (PEO), or a mixture of copolymers of ethylene and octene (PEO).

The first polymer material of the invention can also comprise a grafted polymer, in particular grafted with polar functions.

This grafted polymer advantageously makes it possible to improve the mechanical properties of the first polymer layer.

By way of example, the grafted polymer can be a maleic anhydride grafted olefin polymer, and in particular a maleic anhydride grafted ethylene polymer.

When a grafted polymer is added to the first polymeric material, the first polymeric material may comprise from 1 to 20% by weight of said grafted polymer, and preferably from 1 to 15% by weight of said grafted polymer, relative to the total weight of the first polymeric material in the first composition.

The first polymeric material can have a melt flow index (known as "Melt Flow Index"), in grams / 10 minutes according to ISO 1133 at 190 ° C / 2.16 kg, ranging from 1.0 at 5.

When the composition comprises a mixture of two different olefin polymers, in particular a mixture of ethylene copolymers and of octene, the melt flow indices of these two polymers are different.

The first composition of the invention may comprise at least 30% by weight of said first polymer material, and preferably at least 40% by weight of said first polymer material, relative to the total weight of the first composition.

1.3 The first composition

The first composition can comprise from 20 to 60% by weight of the first oxide relative to the total weight of the first composition. Preferably, the first composition can comprise from 30 to 50% by weight of the first oxide relative to the total weight of the first composition.

The first composition can comprise from 5 to 30% by weight of the second oxide relative to the total weight of the first composition. Preferably, the first composition can comprise from 5 to 20% by weight of the second oxide relative to the total weight of the first composition.

In another preferred embodiment, the first composition may comprise at least 30% by weight of said first charge, and preferably at least 40% by weight of said first charge, relative to the total weight of the first composition.

In another preferred embodiment, the first composition may comprise at least 30% by weight of said first polymer material, and preferably at least 40% by weight of said first polymer material, relative to the total weight of the first composition.

In order to optimize the fire resistance of the cable of the invention, the first composition can have a Mooney viscosity of at least 40, and preferably at least 50. The first composition can have a Mooney viscosity of at most 100, and preferably at most 90.

The Mooney viscosity (ML1 + 4, 160 ° C) is expressed in Mooney units (Me) and can be easily determined by standard NFT 43005.

The first composition may typically further comprise additives in an amount of 0.1 to 20 parts by weight per 100 parts by weight of the first polymeric material in the first composition. Additives are well known to those skilled in the art and can for example be chosen from protective agents (eg anti-UV, anti-copper), implementing agents (eg plasticizers, lubricants), pigments, and antioxidants.

1.4 Characteristics of the first polymer layer

The first polymeric layer can surround one or more elongated conductive element (s).

The first polymeric layer can be an electrically insulating layer.

In the present invention, the term "electrically insulating layer" means a layer whose electrical conductivity can be at most 1.10 ^-9 S / m (siemens per meter) (at 25 ° C), preferably at most 1.10 ^-8 S / m, and preferably at most 1.10 ^-13 S / m (at 25 ° C).

In a particular embodiment, the thickness of the first polymer layer can range from 0.05 mm to 2.0 mm, and preferably from 0.1 mm to 1.0 mm.

In a particular embodiment, the first polymeric layer can be crosslinked or uncrosslinked.

In the present invention, the term “non-crosslinked” is intended to mean a layer whose gel rate according to standard ASTM D2765-01 (xylene extraction) is at most 20%, preferably at most 10%, preferably not more than 5%, and particularly preferably 0%.

In the present invention, the term “crosslinked” is intended to mean a layer whose gel rate according to standard ASTM D2765-01 (extraction with xylene) is at least 50%, preferably at least 80%, and so particularly preferred by at least 90%.

2. The second polymeric layer 2.1 The second charge 2.1.1 The first silicate

The first silicate can be chosen from phyllosilicates, compounds comprising magnesium silicate, compounds comprising aluminum silicate, and one of their mixture.

Preferably, the first silicate can be a phyllosilicate. More particularly, the phyllosilicate can be mica.

The second filler can comprise from 20 to 40% by weight of first silicate relative to the total weight of the second filler.

2.1.2 The second silicate

The second silicate can be a compound with a high specific surface, in particular at least 10 m ² / g, and preferably at least 20 m ² / g. The specific surface is conventionally determined by the BET method according to DIN ISO 9277.

The second silicate can in particular be of the lamellar type.

More particularly, the second silicate can be chosen from phyllosilicates, compounds comprising magnesium silicate, compounds comprising aluminum silicate, and one of their mixture.

Preferably, the second silicate can be a compound comprising magnesium silicate.

More particularly, the compound comprising magnesium silicate can be talc.

The second filler can comprise from 20 to 40% by weight of second silicate relative to the total weight of the second filler.

2.1.3 Other compounds in the second composition

• un oxyde d'un métal alcalino-terreux, et/ou
• un troisième silicate, le troisième silicate étant différent du premier silicate et du deuxième silicate.

In a preferred embodiment, the second charge can also comprise:

• an oxide of an alkaline earth metal, and / or
• a third silicate, the third silicate being different from the first silicate and from the second silicate.

The oxide of an alkaline earth metal advantageously makes it possible to improve the mechanical cohesion properties of the second polymeric layer after combustion under the effect of a flame.

Preferably, the oxide of an alkaline earth metal of the second polymeric layer can be of high purity, in order to improve the electrical resistivity of the cable of the invention.

The term "high purity" means an oxide of an alkaline earth metal having a purity (by calcination) of at least 96.0%, preferably at least 98.0%, and in a particularly preferred manner at least 99.0%.

The oxide of a high purity alkaline earth metal advantageously limits the presence of electrically conductive compound (s), in particular in the form of impurity (s). The impurities may contain, for example, heavy metals. Preferably, the oxide of an alkaline earth metal can comprise at most 30 ppm of heavy metals, and preferably less than 10 ppm of heavy metals.

In a preferred embodiment, the oxide of an alkaline earth metal has a melting temperature of at least 1500 ° C, preferably at least 2000 ° C, and particularly preferably at least 2500 ° C.

Preferably, the oxide of an alkaline earth metal can be magnesium oxide (MgO).

The third silicate can be chosen from phyllosilicates, compounds comprising magnesium silicate, compounds comprising aluminum silicate, and one of their mixture.

Preferably, the third silicate can be a compound comprising aluminum silicate, in particular of the lamellar type.

More particularly, the third silicate can be chosen from montmorillonite, bentonite, kaolinite, hectorite, halloysite, and one of their mixtures.

Preferably, the compound comprising aluminum silicate can be montmorillonite.

As a preferred example of a third silicate, mention may be made of a nanoclay, functionalized or not. More particularly, it can be treated at the surface with cations of the quaternary ammonium type.

The second filler can comprise from 5 to 30% by weight of third silicate relative to the total weight of the second filler in the second composition.

• de 20 à 40 % en poids de premier silicate,
• de 20 à 40 % en poids de deuxième silicate,
• de 5 à 30 % en poids de troisième silicate, et
• de 20 à 40 % en poids d'oxyde d'un métal alcalino-terreux.

In another preferred embodiment, the second load can comprise, relative to the total weight of the second load:

• from 20 to 40% by weight of first silicate,
• from 20 to 40% by weight of second silicate,
• from 5 to 30% by weight of third silicate, and
• from 20 to 40% by weight of oxide of an alkaline earth metal.

2.2 The second polymer material

The second polymer material comprises one or more polymer (s), the term polymer can be understood by any type of polymer well known to those skilled in the art such as homopolymer or copolymer (eg block copolymer, random copolymer, terpolymer, etc. etc).

The polymer can be of the thermoplastic or elastomer type, and can be crosslinked by techniques well known to those skilled in the art.

In a particular embodiment, the second polymer material, or in other words the polymer matrix of the second composition, can comprise one or more olefin polymers, and preferably, one or more ethylene polymer (s) . An olefin polymer is conventionally a polymer obtained from at least one olefin monomer.

More particularly, the second polymer material can comprise more than 30% by weight of olefin polymer (s), preferably more 50% by weight of olefin polymer (s), preferably more than 70% by weight of olefin polymer (s), and more preferably more than 90% by weight of olefin polymer (s) , relative to the total weight of the second polymeric material in the second composition. Preferably, the second polymer material is only composed of one or more olefin polymer (s).

By way of example, the second polymer material of the invention may comprise one or more olefin polymers, and preferably one or more ethylene polymer (s), chosen from a linear low density polyethylene (LLDPE); very low density polyethylene (VLDPE); low density polyethylene (LDPE); medium density polyethylene (MDPE); high density polyethylene (HDPE); an ethylene-propylene elastomeric copolymer (EPM); an ethylene propylene diene monomer terpolymer (EPDM); a copolymer of ethylene and vinyl ester such as a copolymer of ethylene and vinyl acetate (EVA); a copolymer of ethylene and acrylate such as a copolymer of ethylene and butyl acrylate (EBA) or a copolymer of ethylene and methyl acrylate (EMA); a copolymer of ethylene and alpha-olefin such as a copolymer of ethylene and octene (PEO) or a copolymer of ethylene and butene (PEB); and one of their mixtures.

The second polymer material of the invention can also comprise a grafted polymer, in particular grafted with polar functions.

This grafted polymer advantageously makes it possible to improve the mechanical cohesion properties of the second layer after combustion under the effect of a flame.

By way of example, the grafted polymer can be a maleic anhydride grafted olefin polymer, and in particular a maleic anhydride grafted ethylene polymer.

When a grafted polymer is added to the second polymeric material, the second polymeric material can comprise from 1 to 20% by weight of said grafted polymer, and preferably from 5 to 15% by weight of said grafted polymer, relative to the total weight of the second polymeric material in the second composition.

The second polymeric material may comprise a mixture of at least two different ethylene polymers, and more particularly may comprise a mixture of a homopolymer of ethylene and a copolymer of ethylene and vinyl acetate (EVA) .

Preferably, the second polymeric material can comprise from 50 to 80% by weight of EVA and from 20 to 50% by weight of an ethylene homopolymer, relative to the total weight of the second polymeric material in the second composition.

The second composition may comprise at least 30% by weight of the second polymeric material, preferably at least 50% by weight of the second polymeric material, and preferably at least 60% by weight of the second polymeric material, relative to the total weight of the second composition.

2.3 The second composition

The second composition can comprise at least 30% by weight of said second filler relative to the total weight of the second composition.

In a preferred embodiment, the second composition may comprise at least 30% by weight of said second polymeric material relative to the total weight of the second composition.

In order to optimize the fire resistance of the cable of the invention, the second composition can have a Mooney viscosity of at least 50, and preferably at least 55. The second composition can have a Mooney viscosity of at most 100, and preferably at most 90.

The Mooney viscosity (ML1 + 4, 160 ° C) is expressed in Mooney units (Me) and can be easily determined by standard NFT 43005.

The second composition may typically further include additives in an amount of 0.1 to 20 parts by weight per 100 parts by weight of the second polymeric material in the second composition. Additives are well known to those skilled in the art and can for example be chosen from protective agents (eg anti-UV, anti-copper), implementing agents (eg plasticizers, lubricants), pigments , and antioxidants.

2.4 Characteristics of the second polymeric layer

The second polymeric layer may preferably surround the first polymeric layer.

The second polymeric layer can advantageously be non-crosslinked.

In the present invention, the term “non-crosslinked” is intended to mean a layer whose gel rate according to standard ASTM D2765-01 (xylene extraction) is at most 20%, preferably at most 10%, preferably not more than 5%, and particularly preferably 0%.

In another preferred embodiment, the second polymeric layer is an electrically insulating layer.

In the present invention, the term "electrically insulating layer" means a layer whose electrical conductivity can be at most 1.10 ^-9 S / m (siemens per meter) (at 25 ° C), preferably at most 1.10 ^-8 S / m, and preferably at most 1.10 ^-13 S / m (at 25 ° C).

In a particular embodiment, the thickness of the second polymeric layer can range from 0.05 mm to 2.0 mm, and preferably from 0.1 mm to 1.0 mm.

3. Other layer (s)

The cable according to the invention can also comprise a third polymeric layer.

The third polymer layer may preferably surround the second polymer layer.

Preferably, the third polymeric layer can be crosslinked.

In the present invention, the term “crosslinked” is intended to mean a layer whose gel rate according to standard ASTM D2765-01 (extraction with xylene) is at least 50%, preferably at least 80%, and so particularly preferred by at least 90%.

In a preferred embodiment, the third polymeric layer is an electrically insulating layer.

In the present invention, the term "electrically insulating layer" means a layer whose electrical conductivity can be at most 1.10 ^-9 S / m (siemens per meter) (at 25 ° C), preferably at most 1.10 ^-8 S / m, and preferably at most 1.10 ^-13 S / m (at 25 ° C).

In another particular embodiment, the third polymeric layer does not comprise halogenated compounds. Preferably, the third polymeric layer is a so-called "HFFR" layer for anglicism " Halogen-Free Flame Retardant " according to standard IEC 60754 Parts 1 and 2 (2011).

The third polymeric layer may comprise one or more olefin polymer (s) and preferably one or more ethylene polymer (s)

In a particular embodiment, the thickness of the third polymeric layer can range from 0.05 mm to 2 mm, and preferably from 0.1 mm to 1.0 mm.

4. The cable

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

In the present invention, the term "cable" means an electrical and / or optical cable, intended for the transport of energy and / or for the transmission of data.

More particularly, this type of cable comprises one or more elongated conductive element (s) of the electrical and / or optical type.

When the elongated conductive element is of the electrical type, it may be a single conductor such as for example a metallic wire, or a multiconductor such as a plurality of metallic wires, twisted or not.

The elongated electrical conductor can be made from a metallic material chosen in particular from aluminum, an aluminum alloy, copper, a copper alloy, and one of their combinations.

The cross section of the electrical conductor can range from 0.5 mm ² to more than 240 mm ² .

The first polymeric layer can be in direct physical contact with the elongated conductive element.

In a preferred embodiment, the second polymeric layer may surround the first polymeric layer.

When the cable also has a third polymeric layer, the third polymeric layer may surround the first polymeric layer and / or the second polymeric layer.

The cable of the invention may further comprise a protective sheath surrounding one or more elongated conductive element (s) insulated by at least the first polymeric layer, the second polymeric layer, and optionally the third polymeric layer, said three layers being in accordance with the invention.

More particularly, when the cable of the invention comprises a single conductive element insulated by at least the first polymeric layer, the second polymeric layer, and optionally the third polymeric layer, the protective sheath surrounds the single elongated and thus insulated conductive element .

When the cable of the invention comprises several elongated conductive elements insulated by at least the first polymeric layer, the second polymeric layer, and optionally the third polymeric layer, the protective sheath surrounds all of said elongated and thus insulated conductive elements.

The protective sheath of the invention can be a sheath of the tubing type or of the tamping type.

“Tubing sheath” is understood to mean a tube-shaped sheath comprising a substantially identical thickness all along said tube. The tubular sheath can be more or less tight around all of the insulated conductors as previously described, so as in particular to immobilize all of said insulated conductors inside said sheath.

The tubing sheath is very simple and quick to produce since it requires less pressure at the outlet of the extruder than that necessary for the manufacture of a stuffing sheath.

The term "stuffing sheath" means a sheath which fills the interstices, when they exist, between the electrical conductors insulated by at least the first polymeric layer and the second polymeric layer, the volumes of which are accessible.

In a particular embodiment, the thickness of the protective sheath can range from 0.05 mm to 3 mm, and preferably from 0.5 mm to 2.0 mm.

The protective sheath may conventionally be based on one or more olefin polymer (s), with optionally at least one flame-retardant filler such as aluminum trihydroxide (ATH), magnesium dihydroxide (MDH), the chalk. Preferably, the protective sheath is a so-called “HFFR” sheath for Anglicism “ Halogen-Free Flame Retardant ” according to standard IEC 60754 Parts 1 and 2 (2011).

When the cable comprises a protective sheath, it may further comprise a stuffing element positioned along the cable between the protective sheath and the isolated elongated conductive element (s), the stuffing element which can also surround the insulated elongated conductive element (s).

The stuffing element is well known to those skilled in the art and can for example be based on one or more olefin polymer (s), optionally with at least one flame-retardant filler such as, for example, trihydroxide. aluminum (ATH), magnesium dihydroxide (MDH), chalk. Preferably, the stuffing element is a so-called “HFFR” element for “ Halogen-Free Flame Retardant” anglicism according to standard IEC 60754 Parts 1 and 2 (2011).

In order to guarantee a so-called HFFR cable for " Halogen-Free Flame Retardant " anglicism, the cable of the invention, or in other words the elements which compose said cable such as for example the protective sheath, does not include / preferably include no halogenated compounds according to IEC 60754 Parts 1 and 2 (2011). These halogenated compounds can be of all kinds, such as, for example, fluorinated polymers or chlorinated polymers such as polyvinyl chloride (PVC), halogenated plasticizers, halogenated mineral fillers, etc.

• La figure 1 représente une vue schématique en coupe transversale d'un câble électrique selon un premier mode de réalisation conforme à l'invention.
• La figure 2 représente une vue schématique en coupe transversale d'un câble électrique selon un deuxième mode de réalisation conforme à l'invention.

Other characteristics and advantages of the present invention will appear in the light of the description of nonlimiting examples of cables according to the invention made with reference to the figures.

• The figure 1 shows a schematic cross-sectional view of an electric cable according to a first embodiment according to the invention.
• The figure 2 shows a schematic cross-sectional view of an electric cable according to a second embodiment according to the invention.

For reasons of clarity, only the essential elements for the understanding of the invention have been represented schematically, and this without respecting the scale.

The electric cable shown on the figure 1 comprises two electrical conductors 1, each electrical conductor being successively surrounded by a first polymeric layer 2 and a second polymeric layer 3, both according to the invention.

A protective sheath 5 of stuffing type surrounds all of the two conductors insulated by the two polymer layers of the invention.

A packing element 6 is positioned between the protective sheath 5 and all of the electrical conductors insulated by the two polymer layers of the invention. The stuffing element 6 also surrounds all of the electrical conductors insulated by the two polymer layers of the invention.

The electric cable shown on the figure 2 comprises three electrical conductors 1, successively surrounded by a first layer polymer 2 and a second polymer layer 3, both according to the invention. In addition, a third polymeric layer 4 surrounds the second polymeric layer of each of the electrical conductors.

A tubing type protective sheath 5 surrounds all three electrical conductors insulated by the three polymer layers.

Empty spaces 7 are provided between the protective sheath 5 and all of the electrical conductors insulated by the three polymer layers that it surrounds.

All the layers, packing elements and sheaths shown on the Figures 1 and 2 are elements obtained by extrusion. The protective sheath 5 is a conventional sheath produced from a flame-retardant composition based on polyolefin. The packing element 6 is a conventional packing element also produced from a flame-retardant composition based on polyolefin.

Examples

• un premier matériau polymère constitué du Polymère 1 ; et
• une première charge constituée de deux charges différentes à savoir : Oxyde 1 et Oxyde 2.

Tableau 1 1^ère Composition Parties en poids (pcr) des constituants pour 100 parties en poids du 1^er matériau polymère dans la 1^ère com position % en poids des constituants dans la 1^ère composition % en poids des charges dans la 1^ère charge 1^er Matériau polymère Polymère 1 75 35,7 Polymère 2 20 9,5 Polymère 3 5 2,4 1^ère Charge Oxyde 1 90 42,9 81,8 Oxyde 2 20 9,5 18,2 Total 210 100 100 Table 1 below brings together the constituents of a first polymer composition according to the invention with:

• a first polymeric material consisting of Polymer 1; and
• a first charge consisting of two different charges, namely: Oxide 1 and Oxide 2.

<b><u> Table 1 </u></b> 1 ^st Composition Parts by weight (phr) of the constituents per 100 parts by weight of the polymer material ¹ in the 1 ^st position com % By weight of components in the 1 ^st composition % By weight of loads in the load 1 ^era 1 ^st polymer material Polymer 1 75 35.7 Polymer 2 20 9.5 Polymer 3 5 2.4 1 Load ^era Oxide 1 90 42.9 81.8 Oxide 2 20 9.5 18.2 Total 210 100 100

• Polymère 1 est un copolymère d'éthylène et d'octène (PEO) avec une densité de 0,880-0,884 g/cm³, commercialisé par la société EXXONMOBIL sous la référence EXACT 8203 ;
• Polymère 2 est un copolymère d'éthylène et d'octène (PEO), avec une densité de 0,882 g/cm³, et commercialisé par la société EXXONMOBIL sous la référence EXACT 8201 ;
• Polymère 3 est polyéthylène greffé anhydride maléique, avec une densité de 0,912 g/cm³, commercialisé par la société Polieco - MPB sous la référence Coesive LL15M ;
• Oxyde 1 est un oxyde d'un métal alcalino-terreux du type oxyde de magnésium (MgO), commercialisé par la société Van Mannekus sous la référence MgO AK98, avec une pureté de 97,9% ; et
• Oxyde 2 est un dioxyde de silicium (SiO₂) commercialisé par la société EVONIK sous la référence Aerosil R974.

The origin of the various constituents collected in Table 1 is as follows:

• Polymer 1 is a copolymer of ethylene and octene (PEO) with a density of 0.880-0.884 g / cm ³ , sold by the company EXXONMOBIL under the reference EXACT 8203;
• Polymer 2 is a copolymer of ethylene and octene (PEO), with a density of 0.882 g / cm ³ , and sold by the company EXXONMOBIL under the reference EXACT 8201;
• Polymer 3 is maleic anhydride grafted polyethylene, with a density of 0.912 g / cm ³ , sold by the company Polieco - MPB under the reference Coesive LL15M;
• Oxide 1 is an oxide of an alkaline earth metal of the magnesium oxide (MgO) type, sold by the company Van Mannekus under the reference MgO AK98, with a purity of 97.9%; and
• Oxide 2 is a silicon dioxide (SiO ₂ ) sold by the company EVONIK under the reference Aerosil R974.

• un deuxième matériau polymère constitué de trois polymères différents, à savoir : Polymère 10, Polymère 20 et Polymère 30 ; et
• une deuxième charge constituée de quatre charges différentes, à savoir : Silicate 10, Silicate 20, Silicate 30 et Oxyde 10.

Tableau 2 2^ème Composition Parties en poids (pcr) des constituants pour 100 parties en poids du 2^ème matériau polymère dans la 2^ème com position % en poids des constituants dans la 2^ème composition polymère % en poids des charges dans la 2^ème charge 2^ème Matériau polymère Polymère 10 60 23,3 Polymère 20 30 11,7 Polymère 30 10 3,9 2^ème charge Silicate 10 45 17,5 29,4 Silicate 20 45 17,5 29,4 Silicate 30 18 7,0 11,8 Oxyde 10 45 17,5 29,4 Additifs Plastifiant 1 0,4 Antioxydant 3 1,2 Total 257 100 100 Table 2 below brings together the constituents of a second composition according to the invention with:

• a second polymer material consisting of three different polymers, namely: Polymer 10, Polymer 20 and Polymer 30; and
• a second charge consisting of four different charges, namely: Silicate 10, Silicate 20, Silicate 30 and Oxide 10.

<b><u> Table 2 </u></b> 2 ^nd Composition Parts by weight (pcr) of the constituents per 100 parts by weight of the 2 ^nd polymer material in the 2 ^nd position % by weight of the constituents in the ^2nd polymer composition % by weight of the charges in the ^2nd charge ^2nd polymer material Polymer 10 60 23.3 Polymer 20 30 11.7 Polymer 30 10 3.9 ^2nd charge Silicate 10 45 17.5 29.4 Silicate 20 45 17.5 29.4 Silicate 30 18 7.0 11.8 Oxide 10 45 17.5 29.4 Additives Plasticizer 1 0.4 Antioxidant 3 1.2 Total 257 100 100

• Polymère 10 est un copolymère d'éthylène et d'acétate de vinyle (EVA), avec une densité de 0,950 g/cm³, commercialisé par la société Exxon Mobil sous la référence Elvax 2803 ;
• Polymère 20 est un polyéthylène basse densité, avec une densité de 0,900 g/cm³, commercialisé par la société Polimeri Europa sous la référence Clearflex FFDO ;
• Polymère 30 est un polyéthylène greffé anhydride maléique, avec une densité de 0,912 g/cm³, commercialisé par la société Polieco - MPB sous la référence Coesive LL15M ;
• Silicate 10 est un silicate du type mica, commercialisé par la société Keyser and Mackay sous la référence Mica SX300 ;
• Silicate 20 est un silicate lamellaire du type talc, commercialisé par la société Univar sous la référence Mistron HAR, avec une surface spécifique de 22 m²/g (méthode B.E.T. selon la norme DIN ISO 9277) ;
• Silicate 30 est un silicate lamellaire du type montmorillonite, commercialisé par la société BYK sous la référence Cloisite 20 ;
• Oxyde 10 est un oxyde d'un métal alcalino-terreux du type oxyde de magnésium (MgO) de grade pharmaceutique, commercialisé par la société SCORA sous la référence MgO PE leger, avec une pureté (par calcination) de 99,0%, et une température de fusion d'environ 2800°C ;
• Plastifiant est une cire commercialisée par la société Clariant sous la référence Cire PE 520 ; et
• Antioxydant est un antioxydant commercialisé par la société Chemtura sous la référence Naugard XL1.

The origin of the various constituents collected in Table 2 is as follows:

• Polymer 10 is a copolymer of ethylene and vinyl acetate (EVA), with a density of 0.950 g / cm ³ , sold by the company Exxon Mobil under the reference Elvax 2803;
• Polymer 20 is a low density polyethylene, with a density of 0.900 g / cm ³ , sold by the company Polimeri Europa under the reference Clearflex FFDO;
• Polymer 30 is a grafted polyethylene of maleic anhydride, with a density of 0.912 g / cm ³ , sold by the company Polieco - MPB under the reference Coesive LL15M;
• Silicate 10 is a silica of the mica type, sold by the company Keyser and Mackay under the reference Mica SX300;
• Silicate 20 is a lamellar silicate of the talc type, sold by the company Univar under the reference Mistron HAR, with a specific surface of 22 m ² / g (BET method according to DIN ISO 9277);
• Silicate 30 is a lamellar silicate of the montmorillonite type, sold by the company BYK under the reference Cloisite 20;
• Oxide 10 is an alkaline earth metal oxide of the pharmaceutical grade magnesium oxide (MgO) type, sold by the company SCORA under the reference MgO PE light, with a purity (by calcination) of 99.0%, and a melting temperature of around 2800 ° C;
• Plasticizer is a wax sold by the company Clariant under the reference Wax PE 520; and
• Antioxidant is an antioxidant marketed by the company Chemtura under the reference Naugard XL1.

• NF C 32-070 CR1 (2001),
• DIN4102-12 avec la performance E30, E60, E90, et
• NBN 713020 Addendum 3 avec la performance Rf60, Rf90, Rf120.

In order to check the fire resistance of the compositions of the invention in operational configuration, the polymer layers in accordance with the invention were used in different types of cables (see tables 3 and 4 below) in order to be tested. with regard to the following standards:

• NF C 32-070 CR1 (2001),
• DIN4102-12 with performance E30, E60, E90, and
• NBN 713020 Addendum 3 with performance Rf60, Rf90, Rf120.

Table 3 below presents a cable comprising a first polymeric layer obtained from the first composition of table 1, and a second polymeric layer obtained from the second composition of table 2.

• quatre conducteurs électriques entourés respectivement par une isolation tricouche, ladite isolation tricouche comprenant une première couche polymérique selon l'invention, obtenue à partir de la première composition polymère du tableau 1, une deuxième couche polymérique selon l'invention, obtenue à partir de la deuxième composition du tableau 2, et une troisième couche polymérique selon un mode de réalisation particulier de l'invention,
• un élément de bourrage entourant les quatre conducteurs électriques isolés, et
• une gaine de protection du type bourrante entourant les quatre conducteurs électriques isolés ainsi que l'élément de bourrage.

Tableau 3 Câble 1 Nombre de conducteurs électriques isolés 4 Section d'un conducteur électrique en cuivre (mm²) 1,5 1^ère couche polymérique / Epaisseur (mm) Composition selon tableau 1 / 0,5 2^ème couche polymérique / Epaisseur (mm) Composition selon tableau 2 / 0,2 3^ème couche polymérique / Epaisseur (mm) HFFR1 / 0,3 Epaisseur totale (mm) de l'isolant 1,0 Elément de bourrage Oui : HFFR2 Epaisseur (mm) de la gaine de protection tubante HFFR3 1,3 Diamètre extérieur du câble électrique 14.2 Test NF C 32-070 CR1 (2001) 65 min Test DIN4102-12 Performance E90 90 min Test NBN 713020 Addendum 3 Performance Rf120 120 min More particularly, the cable 1 of table 3 comprises:

• four electrical conductors respectively surrounded by a three-layer insulation, said three-layer insulation comprising a first polymeric layer according to the invention, obtained from the first polymer composition of table 1, a second polymeric layer according to the invention, obtained from the second composition of table 2, and a third polymeric layer according to a particular embodiment of the invention,
• a stuffing element surrounding the four insulated electrical conductors, and
• a tamping type protective sheath surrounding the four insulated electrical conductors as well as the tamping element.

<b><u> Table 3 </u></b> Cable 1 Number of insulated electrical conductors 4 Cross-section of an electrical copper conductor (mm ² ) 1.5 1 ^st polymer layer / Thickness (mm) Composition according to table 1 / 0.5 ^2nd polymeric layer / Thickness (mm) Composition according to table 2 / 0.2 ^3rd polymeric layer / Thickness (mm) HFFR1 / 0.3 Total thickness (mm) of insulation 1.0 Stuffing element Yes: HFFR2 Thickness (mm) of the HFFR3 protective tubing 1.3 Outside diameter of the electric cable 14.2 NF C 32-070 CR1 test (2001) 65 mins Test DIN4102-12 Performance E90 90 mins NBN 713020 Addendum 3 Performance Rf120 test 120 mins

• HFFR1 est une couche extrudée HFFR à base de polyoléfine chargée(s), la/les polyoléfine(s) étant du type copolymère(s) d'éthylène et d'acétate de vinyl (EVA), et la charge étant au moins une charge ignifugeante du type trihydroxyde d'aluminium ;
• HFFR2 est un élément de bourrage extrudé HFFR à base de polyoléfine(s) chargée(s), la/les polyoléfine(s) étant du type copolymère(s) d'éthylène et d'acétate de vinyl (EVA), et la charge étant au moins une charge ignifugeante du type trihydroxyde d'aluminium ; et
• HFFR3 est une gaine extrudée HFFR à base de polyoléfine(s) chargée(s), la/les polyoléfine(s) étant du type copolymère(s) d'éthylène et d'acétate de vinyl (EVA), et la charge étant au moins une charge ignifugeante du type trihydroxyde d'aluminium.

The origin of the elements gathered in table 3 is as follows:

• HFFR1 is an HFFR extruded layer based on charged polyolefin (s), the polyolefin (s) being of the copolymer (s) type of ethylene and vinyl acetate (EVA), and the filler being at least one filler flame retardant of the aluminum trihydroxide type;
• HFFR2 is an HFFR extruded stuffing element based on charged polyolefin (s), the polyolefin (s) being of the copolymer (s) type of ethylene and vinyl acetate (EVA), and the filler being at least one flame retardant filler of the aluminum trihydroxide type; and
• HFFR3 is an HFFR extruded sheath based on charged polyolefin (s), the polyolefin (s) being of the copolymer (s) type of ethylene and vinyl acetate (EVA), and the filler being at minus a flame retardant filler of the aluminum trihydroxide type.

Preparation process

Firstly, the first composition of table 1 is extruded, using a conventional single screw extruder, around each electrical conductor, thus forming the first insulating polymeric layer.

The temperature profile ranges from 90 to 200 ° C, and the extruder has eight heating zones.

In a second step, the second composition of table 2 is conventionally extruded around the first polymeric layer, thus forming the second insulating polymeric layer.

In a third step, a third layer as defined in the invention, when it exists, is extruded around the two previous layers.

The two-layer or three-layer insulation can be extruded in several successive stages, but it can also be extruded by co-extrusion (one and the same extrusion head).

• l'élément de bourrage lorsqu'il existe, et
• la gaine de protection.

The rest of the constituent elements of the cable 1 is extruded successively or in tandem, namely:

• the stuffing element when it exists, and
• the protective sheath.

Test used

• au test selon la norme NF C 32-070 CR1 (2001),
• au test selon la norme DIN4120-12, et
• au test selon la norme NBN 713020 Addendum 3,

les résultats de ces tests étant rassemblés dans le tableau 3.Cable 1 is subject to:

• to the test according to standard NF C 32-070 CR1 (2001),
• to the test according to DIN4120-12, and
• to the test according to standard NBN 713020 Addendum 3,

the results of these tests are collated in table 3.

Standard NF C 32-070 CR1 (2001) indicates in particular a fire resistance threshold of 65 minutes (min) to validate the performance.

The DIN4120-12 standard indicates in particular a fire resistance threshold of 30, 60 and 90 minutes (min) to validate the performance E30, E60 and E90 respectively.

NBN standard 713020 Addendum 3 indicates in particular a fire resistance threshold of 60, 90 and 120 minutes (min) to validate the performance rf60, rf90 and rf120 respectively.

The results clearly show that a cable comprising the two polymeric layers of the invention, whatever its structure, makes it possible to advantageously satisfy various standards of fire resistance, in particular the standards NF C 32-070 CR1 (2001), DIN4102- 12 (E90), and NBN 713020 Addendum 3 (Rf120), presenting a significantly improved fire resistance.

Claims (17)

1. A cable comprising at least one elongated conductive element (1) sheathed by at least:

   - a first polymeric layer (2) obtained from a first composition comprising a first polymer material and a first filler; and

   - a second polymeric layer (3) obtained from a second composition comprising a second polymer material and a second filler;

   characterised in that:

   - the said first filler comprises at least a first oxide of such type as the oxide of an alkaline earth metal; and

   - the said second filler comprises at least a first silicate and a second silicate, the second silicate being different from the first silicate.
2. A cable according to claim 1, characterised in that the first oxide is magnesium oxide (MgO).
3. A cable according to claim 1 or 2, characterised in that the first filler also comprises a second oxide which is different from the first oxide.
4. A cable according to claim 3, characterised in that the second oxide is silicon dioxide (SiO₂).
5. A cable according to any one of the preceding claims, characterised in that the first composition comprises from 20 to 60% by weight of the first oxide in relation to the total weight of the first composition.
6. A cable according to any one of claims 3 to 5, characterised in that the first composition comprises from 5 to 30% by weight of the second oxide in relation to the total weight of the first composition.
7. A cable according to any one of the preceding claims, characterised in that the first composition comprises at least 30% by weight of the said first filler, and preferably 40% by weight of the said first filler, in relation to the total weight of the first composition.
8. A cable according to any one of the preceding claims, characterised in that the first polymer material comprises one or more ethylene polymer(s).
9. A cable according to any one of the preceding claims, characterised in that the first polymer material comprises at least one copolymer of ethylene and octane, ie ethylene-octene copolymer.
10. A cable according to any one of the preceding claims, characterised in that the second filler in addition comprises an oxide of an alkaline earth metal.
11. A cable according to claim 10, characterised in that the alkaline earth metal oxide is magnesium oxide (MgO).
12. A cable according to any one of the preceding claims, characterised in that the second filler in addition comprises a third silicate, the third silicate being different from the first silicate and from the second silicate.
13. A cable according to claim 12, characterised in that the second filler comprises, in relation to the total weight of the second filler:

    - from 20 to 40% by weight of the first silicate;

    - from 20 to 40% by weight of the second silicate;

    - from 5 to 30% by weight of the third silicate; and

    - from 20 to 40% by weight of the oxide of an alkaline earth metal.
14. A cable according to claim 2 or 11, characterised in that the alkaline earth metal oxide has a purity (obtained by means of calcination) of at least 96.0%, and preferably of at least 98.0%.
15. A cable according to any one of the preceding claims, characterised in that the first polymeric layer (2) is an electrically insulating layer.
16. A cable according to any one of the preceding claims, characterised in that the second polymeric layer (3) is an electrically insulating layer.
17. A cable according to any one of the preceding claims, characterised in that the first polymeric layer (2) is sheathed by the second polymeric layer (3).

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