EP3404673A1 - Fire resistant cable - Google Patents

Abstract

The present invention relates to a cable comprising at least one elongate conductive element (1) surrounded 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, characterized in that said first filler comprises at least a first oxide of the alkaline earth metal oxide type, and said second filler comprises at least a first silicate and a second silicate, the second silicate being different from the first silicate.

Description

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

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

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

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 in particular, it is indeed essential to maximize the capabilities of the cable to delay the spread of flames on the one hand, and resist fire on the other hand to ensure continuity of operation.

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. In case of fire, the cable must be able to withstand the fire in order to operate 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 release toxic fumes and / or opaque when subjected to extreme thermal conditions.

Of the document EP-0 942 439 is known a fire-resistant and halogen-free electrical safety cable comprising a set of insulated electrical conductors, said assembly being surrounded by an outer 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 ceramics at high temperatures corresponding to fire conditions. The polymeric material of this single insulating layer is selected from a polysiloxane, an ethylene copolymer, and their mixture.

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

The purpose of the present invention is to overcome the drawbacks of prior art techniques by proposing in particular a cable having excellent fire resistance properties while limiting the risk of mechanical degradation of the electrical conductors or conduct that 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 present invention relates to 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 filler comprises at least a first oxide of alkaline earth metal oxide type, 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 a very good fire resistance, and in particular reduces significantly or even prevent the formation of inflamed droplets during the combustion of the cable. Properties mechanical 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:

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

The invention as defined in this way 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 polymeric layer 1.1 The first charge

The alkaline earth metal oxide advantageously improves the high temperature electrical resistivity properties of the first polymeric layer under the conditions of a fire.

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

"High purity" is understood to mean an alkaline earth metal oxide having a purity (by calcination) of at least 96.0%, preferably at least 98.0%, and particularly preferably at least 99.0%.

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

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

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

The first charge may further comprise a second oxide different from the first oxide.

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

The first charge may comprise from 50 to 90% by weight of the first oxide with respect to the total weight of the first charge.

The first charge may comprise from 10 to 30% by weight of the second oxide with respect to the total weight of the first charge.

1.2 The first polymer material

The first polymeric material of the invention comprises one or more polymer (s), the term polymer being 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 may be of the thermoplastic or elastomeric type, and may be crosslinked by techniques well known to those skilled in the art.

In a particular embodiment, the first polymeric material, or in other words the polymer matrix of the first composition, may 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 may 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 particularly preferably more than 90% by weight of olefin polymer (s), based on the total weight of the first polymer material in the first composition. Preferably, the first polymeric material is composed solely 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 polymers, chosen from a linear low density polyethylene (LLDPE); a 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 an ethylene-octene copolymer (PEO) or a copolymer of ethylene and butene (PEB); and one of their mixtures. The preferred ethylene polymer is the ethylene-octene copolymer (PEO), or a mixture of ethylene-octene (PEO) copolymers.

The first polymeric material of the invention may further comprise a graft polymer, in particular grafted with polar functions.

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

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

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

The first polymer material may have a melt flow index (known by the Anglicism "Melt Flow Index"), in gram / 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, especially a mixture of copolymers of ethylene 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 may comprise from 20 to 60% by weight of the first oxide relative to the total weight of the first composition. Preferably, the first composition may comprise from 30 to 50% by weight of the first oxide relative to the total weight of the first composition.

The first composition may comprise from 5 to 30% by weight of the second oxide relative to the total weight of the first composition. Preferably, the first composition may 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 filler, and preferably at least 40% by weight of said first filler, based on the total weight of the first composition.

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

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

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

The first composition may typically additionally 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. The additives are well known to those skilled in the art and may be chosen for example from protection agents (eg anti-UV, anti-copper), processing agents (eg plasticizers, lubricants), pigments, and antioxidants.

1.4 Characteristics of the first polymeric layer

The first polymeric layer may surround one or more elongated conductive member (s).

The first polymeric layer may 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 polymeric layer may 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 may be crosslinked or uncrosslinked.

In the present invention, the term "non-crosslinked" means a layer whose gel level according to ASTM D2765-01 (xylene extraction) is at most 20%, preferably at most 10%, preferably at most 5%, and particularly preferably 0%.

In the present invention, the term "crosslinked" means a layer whose gel level according to ASTM D2765-01 (xylene extraction) is at least 50%, preferably at least 80%, and so particularly preferred at least 90%.

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

The first silicate may be selected from phyllosilicates, compounds comprising magnesium silicate, compounds comprising aluminum silicate, and a mixture thereof.

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

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

The second silicate may in particular be of lamellar type.

More particularly, the second silicate may be chosen from phyllosilicates, compounds comprising magnesium silicate, compounds comprising aluminum silicate, and a mixture thereof.

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

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

The second filler may 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 load may further include:

• an oxide of an alkaline earth metal, and / or
• a third silicate, the third silicate being different from the first silicate and 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 alkaline earth metal oxide of the second polymeric layer may be of high purity, in order to improve the electrical resistivity of the cable of the invention.

"High purity" is understood to mean an alkaline earth metal oxide having a purity (by calcination) of at least 96.0%, preferably at least 98.0%, and particularly preferably at least 99.0%.

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

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

Preferably, the alkaline earth metal oxide may be magnesium oxide (MgO).

The third silicate may be selected from phyllosilicates, compounds comprising magnesium silicate, compounds comprising aluminum silicate, and a mixture thereof.

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

More particularly, the third silicate may be chosen from montmorillonite, bentonite, kaolinite, hectorite, halloysite, and a mixture thereof.

Preferably, the compound comprising aluminum silicate may be montmorillonite.

As a preferred example of a third silicate, there may be mentioned a nanoclay, functionalized or otherwise. More particularly, it can be surface treated with quaternary ammonium cations.

The second filler may 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 may comprise, based on 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 alkaline earth metal oxide.

2.2 The second polymeric material

The second polymer material comprises one or more polymer (s), the term polymer being 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 may be of the thermoplastic or elastomeric type, and may be crosslinked by techniques well known to those skilled in the art.

In a particular embodiment, the second polymeric material, or in other words the polymer matrix of the second composition, may 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 second polymeric material may comprise more than 30% by weight of olefin polymer (s), more preferably 50% by weight of olefin polymer (s), preferably more than 70% by weight of olefin polymer (s), and particularly 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 polymeric material is composed solely of one or more olefin polymer (s).

By way of example, the second polymeric material of the invention may comprise one or more olefin polymers, and preferably one or more ethylene polymers, chosen from a linear low density polyethylene (LLDPE); a 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 an ethylene-octene copolymer (PEO) or a copolymer of ethylene and butene (PEB); and one of their mixtures.

The second polymeric material of the invention may further comprise a graft 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 graft polymer may be a maleic anhydride grafted olefin polymer, and in particular a maleic anhydride grafted ethylene polymer.

When a graft polymer is added to the second polymer material, the second polymer material may comprise from 1 to 20% by weight of said graft polymer, and preferably from 5 to 15% by weight of said graft 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 blend of a homopolymer of ethylene and a copolymer of ethylene and vinyl acetate (EVA) .

Preferably, the second polymeric material may comprise from 50 to 80% by weight of EVA and from 20 to 50% by weight of an ethylene homopolymer, based on 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 polymer material, preferably at least 50% by weight of the second polymer material, and preferably at least 60% by weight of the second polymer material, relative to the total weight of the second composition.

2.3 The second composition

The second composition may 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 polymer 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 may have a Mooney viscosity of at least 50, and preferably at least 55. The second composition may have a Mooney viscosity of at most 100, and preferably at most 90.

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

The second composition may typically additionally comprise 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 may for example be chosen from protective agents (eg anti-UV, anti-copper), processing 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 may advantageously be uncrosslinked.

In the present invention, the term "non-crosslinked" means a layer whose gel level according to ASTM D2765-01 (xylene extraction) is at most 20%, preferably at most 10%, preferably at most 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 may 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 may further comprise a third polymeric layer.

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

Preferably, the third polymeric layer may be crosslinked.

In the present invention, the term "crosslinked" means a layer whose gel level according to ASTM D2765-01 (xylene extraction) is at least 50%, preferably at least 80%, and so particularly preferred 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 the Anglicism "Halogen-Free Flame Retardant" according to 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 may 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" is understood to mean an electrical and / or optical cable, intended for the transmission of energy and / or 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 electric type, it may be a single conductor such as for example a metal wire, or a multiconductor such as a plurality of metal wires, twisted or not.

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

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

The first polymeric layer may be in direct physical contact with the elongate conductive member.

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

When the cable further 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) isolated 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 isolated by at least the first polymeric layer, the second polymeric layer, and optionally the third polymeric layer, the protective sheath surrounds the single elongate conductive element and thus isolated .

When the cable of the invention comprises a plurality of elongated conductive elements isolated 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 conductive elements and thus isolated.

The protective sheath of the invention may be a sheath of the tubular type or the stuffing type.

The term "tubular sheath" means a tube-shaped sheath comprising a substantially identical thickness all along said tube. The tubular sheath may be more or less tight around all the insulated conductors as previously described, in particular to immobilize all of said insulated conductors inside said sheath.

The tubular sheath is very simple and quick to perform since it requires a pressure at the exit of the extruder smaller than that required for the manufacture of a stuffing sheath.

The term "cladding sheath" means a sheath that fills the interstices, when they exist, between the electrical conductors isolated by at least the first polymeric layer and the second polymeric layer, whose volumes 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 be conventionally based on one or more olefin polymers, optionally with 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 the " Halogen-Free Flame Retardant " anglicism according to 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 at least one elongate conductive element (s), stuffing element which may further surround the at least one elongated conductive member (s).

The stuffing element is well known to those skilled in the art and may for example be based on one or more olefin polymer (s), with optionally 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 the Anglicism " Halogen-Free Flame Retardant" according to IEC 60754 Parts 1 and 2 (2011).

In order to guarantee a so-called HFFR cable for the " Halogen-Free Flame Retardant " anglicism, the cable of the invention, or in other words the elements that make up said cable, such as, for example, the protective sheath, do not include / preferably include no halogenated compounds according to IEC 60754 Parts 1 and 2 (2011). These halogenated compounds may be of any kind, 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 features and advantages of the present invention will appear in the light of the description of non-limiting examples of cables according to the invention made with reference to the figures.

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

For the sake of clarity, only the essential elements for understanding the invention have been shown schematically, and this without respect of 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 in accordance with the invention.

A tamper-type protective sheath 5 surrounds all of the two insulated conductors by the two polymeric layers of the invention.

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

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

A tubular type protective sheath 5 surrounds all three electrical conductors isolated by the three polymeric layers.

Blank spaces 7 are formed between the protective sheath 5 and all the electrical conductors isolated by the three polymeric layers it surrounds.

The set of layers, stuffing elements and sheaths represented on the Figures 1 and 2 are elements obtained by extrusion. The protective sheath 5 is a conventional sheath made from a flame retardant composition based on polyolefin. The stuffing element 6 is a conventional stuffing element also made from a flame retardant polyolefin composition.

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 groups 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 Composition ^era 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 polymeric 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 different constituents listed 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 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 Exxon Mobil under the reference EXACT 8201;
• Polymer 3 is maleic anhydride grafted polyethylene, with a density of 0.912 g / cm ³ , marketed by 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 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 collates the constituents of a second composition according to the invention with:

• a second polymeric 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> ^2nd Composition Parts by weight (phr) of the constituents per 100 parts by weight of the 2 ^nd polymer material in the 2 ^nd position com % By weight of components in the 2 ^nd 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 different constituents listed 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 Exxon Mobil under the reference Elvax 2803;
• Polymer 20 is a low density polyethylene with a density of 0.900 g / cm ³ marketed by Polimeri Europa under the trade name Clearflex FFDO;
• Polymer 30 is a maleic anhydride grafted polyethylene with a density of 0.912 g / cm ³ marketed by Polieco - MPB under the reference Coesive LL15M;
• Silicate 10 is a mica silicate, sold by Keyser and Mackay under the reference Mica SX300;
• Silicate 20 is a talc type silicate, marketed by Univar under the reference Mistron HAR, with a specific surface area of 22 m ² / g (BET method according to DIN ISO 9277);
• Silicate 30 is a lamellar silicate of the montmorillonite type, sold by BYK under the reference Cloisite 20;
• Oxide 10 is an oxide of an alkaline earth metal of the magnesium oxide type (MgO) of pharmaceutical grade marketed by the company SCORA as MgO PE light, with a purity (by calcination) of 99.0%, and a melting temperature of about 2800 ° C;
• Plasticizer is a wax sold by Clariant under the reference Wax PE 520; and
• Antioxidant is an antioxidant marketed by 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 verify the fire resistance of the compositions of the invention in operational configuration, the polymeric layers in accordance with the invention were used in different types of cables (see Tables 3 and 4 below) in order to be tested. according to the following standards:

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

Table 3 below shows 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 surrounded respectively by a trilayer 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 tamper-type protective sheath surrounding the four insulated electrical conductors as well as the stuffing element.

<b><u> Table 3 </ u></b> Cable 1 Number of isolated electrical conductors 4 Section of a copper electrical conductor (mm ² ) 1.5 1 ^st polymeric layer / Thickness (mm) Composition according to table 1 / 0,5 ^2nd polymeric layer / Thickness (mm) Composition according to table 2 / 0,2 3 ^rd polymeric layer / Thickness (mm) HFFR1 / 0.3 Total thickness (mm) of the insulation 1.0 Stuffing element Yes: HFFR2 Thickness (mm) of tubular protection sheath HFFR3 1.3 Outside diameter of the electric cable 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

• 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 collected in Table 3 is as follows:

• HFFR1 is an extruded polyolefin-based HFFR-based film, 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 extruded padding member HFFR based on charged polyolefin (s), the polyolefin (s) being of the copolymer type (s) of ethylene and vinyl acetate (EVA), and the charge being at least one flame retardant filler of the aluminum trihydroxide type; and
• HFFR3 is an extruded sheath HFFR based polyolefin (s) loaded (s), the polyolefin (s) being of the copolymer type (s) of ethylene and vinyl acetate (EVA), and the load being at less a flame retardant filler of the aluminum trihydroxide type.

Preparation process

In a first step, 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 bilayer or trilayer insulation can be extruded in several successive steps, but it can also be extruded by coextrusion (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:

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

the results of these tests are collated in Table 3.

The 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 specifies a fire resistance threshold of 30, 60 and 90 minutes (min) to validate the performance E30, E60 and E90, respectively.

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

The results clearly show that a cable comprising the two polymeric layers of the invention, whatever its structure, makes it possible to advantageously satisfy different standards of fire resistance, in particular NF C 32-070 CR1 (2001), DIN 4102- 12 (E90), and NBN 713020 Addendum 3 (Rf120), with significantly improved fire resistance.

Claims (17)

Cable comprising at least one elongated conductive element (1) surrounded 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, characterized in that said first filler comprises at least a first oxide of the alkaline earth metal oxide type, and said second filler comprises at least a first silicate and a second silicate, the second silicate being different from the first silicate. Cable according to claim 1, characterized in that the first oxide is magnesium oxide (MgO). Cable according to claim 1 or 2, characterized in that the first charge further comprises a second oxide different from the first oxide. Cable according to claim 3, characterized in that the second oxide is silicon dioxide (SiO ₂ ). Cable according to any one of the preceding claims, characterized in that the first composition comprises from 20 to 60% by weight of the first oxide relative to the total weight of the first composition. Cable according to any one of claims 3 to 5, characterized in that the first composition comprises from 5 to 30% by weight of the second oxide relative to the total weight of the first composition. Cable according to any one of the preceding claims, characterized in that the first composition comprises at least 30% by weight of said first filler, and preferably 40% by weight of said first filler, relative to the total weight of the first composition . Cable according to any one of the preceding claims, characterized in that the first polymer material comprises one or more ethylene polymer (s). Cable according to any one of the preceding claims, characterized in that the first polymer material comprises at least one copolymer of ethylene and octene. Cable according to any one of the preceding claims, characterized in that the second charge further comprises an oxide of an alkaline earth metal. Cable according to claim 10, characterized in that the oxide of an alkaline earth metal is magnesium oxide (MgO). Cable according to any one of the preceding claims, characterized in that the second charge further comprises a third silicate, the third silicate being different from the first silicate and the second silicate. Cable according to Claim 12, characterized in that the second load comprises, 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 alkaline earth metal oxide. Cable according to claim 2 or 11, characterized in that the alkaline earth metal oxide has a purity (by calcination) of at least 96.0%, and preferably at least 98.0%. Cable according to any one of the preceding claims, characterized in that the first polymeric layer (2) is an electrically insulating layer. Cable according to any one of the preceding claims, characterized in that the second polymeric layer (3) is an electrically insulating layer. Cable according to any one of the preceding claims, characterized in that the second polymeric layer (3) surrounds the first polymeric layer (2).

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