Cable containing a recyclable polymer layer

Abstract

The invention relates to an electrical cable comprising, around at least one elongated conductive element, a recyclable thermoplastic layer comprising at least: - a composite material (TPV) comprising: a thermoplastic polymer matrix (a); and a vulcanized elastomer phase (b) dispersed within said thermoplastic matrix (a); and - polyethylene. Figure for the abstract: none

Description

Description Title of the invention: Cable comprising a polymer layer re- cycling

[0001] — The present invention relates to the field of electrical devices of the cable type electrical or electrical cable accessories and which include at least one recyclable polymer layer. By "polymer layer," we mean here a coating with based on at least one polymer.

[0002] — The invention typically, but not exclusively, applies to the fields of low voltage (especially below 6kV) or medium voltage power cables (particularly from 6 to 45-60 kV), whether direct or alternating current.

[0003] — Power cables typically comprise a central electrical conductor, ge- generally at least one elongated electrically conductive element of the wire or strand type wires, and at least one electrically insulating layer surrounding this conductive element central. Optionally, a power cable may also include at least one semiconductor layer, which can, for example, be, depending on the intended applications: - possibly an internal semiconductor layer, located between the electrical layer triple insulating and the central conducting element (where applicable, the semi-semi layer) internal conductor surrounds the central conducting element and the electrically (insulating material is located around the inner semiconductor layer); and / or - possibly an external semiconductor layer surrounding said electrical layer trically insulating.

[0004] — Conventionally, these layers are made from cross-linked polymers, in particular based on a cross-linked polyolefin such as cross-linked polyethylene (XLPE) or based on of a cross-linked elastomer, for example a cross-linked ethylene-propylene-diene (EPDM). The use of cross-linked polymers is well known to improve certain properties of the layers, including their mechanical and thermal properties. However, polymer crosslinking presents one particular problem, namely that it makes recycling very difficult (and often even impossible in practice) polymer layers.

[0005] — More recently, it has been proposed, among other things, in the patent application W0O2018167442, to use polypropylene-based diapers, which present the advantage of not having to be cross-linked, thus opening up the possibility of a Easier recycling. Polypropylene-based diapers generally have good dielectric properties, but less mechanical and thermal properties interesting than those of cross-linked layers. In particular, the low density of poly- propylene is associated with lower thermal conductivity properties than those polyethylene, which is particularly a disadvantage for medium or high voltage power cables: this lower thermal conductivity reduces the dissipation of heat generated by the Joule effect, which negatively impacts the amount of energy transportable by the cable. One aim of the present invention is to provide cables comprising one or more recyclable insulating or semiconducting layers, and which exhibit good dielectric, mechanical, and thermal properties. To this end, the present invention proposes to use within these layers a mixture of a composite material called TPV (for the English "thermoplastic vulcanizate") and a polyethylene. More specifically, according to a first aspect, the present invention relates to an electrical cable comprising, around at least one elongated conductive element, a recyclable thermoplastic layer comprising at least - a composite material (also referred to below as "TPV" for brevity) comprising: (a) a thermoplastic polymer matrix; and (b) a vulcanized elastomeric phase dispersed within said thermoplastic matrix (a); and - polyethylene. In a preferred configuration, the dispersed vulcanized elastomer phase (b) comprises a crosslinked ethylene-propylene-diene (EPDM) elastomer. Advantageously, the dispersed vulcanized elastomer phase (b) consists solely of a vulcanized EPDM elastomer. Alternatively, other crosslinked elastomers may be present in the vulcanized elastomer phase (b), alone or in mixture with EPDM, for example a crosslinked ethylene-propylene elastomer. Furthermore, it is advantageous for the thermoplastic matrix (a) to comprise a polyolefin. Here, "polyolefin" is understood to mean a copolymer or homopolymer of olefin, preferably a non-cyclic olefin such as ethylene or propylene. Advantageously, the thermoplastic matrix (a) comprises a homopolymer or copolymer of propylene, for example, a polypropylene homopolymer. In a preferred mode, the matrix (a) consists solely of a polypropylene homopolymer. Thus, in an interesting configuration, the TPV composite material comprises a polypropylene-based matrix (a) in which a crosslinked EPDM-based phase (b) is dispersed. For example, it could be a matrix (a) consisting solely of polypropylene in which a dispersed phase (b) consisting solely of crosslinked EPDM is dispersed. According to an interesting embodiment of the invention, the recyclable thermoplastic layer comprising the TPV and polyethylene may further comprise a propylene copolymer (c), which is preferably a copolymer of propylene and an alpha olefin distinct from propylene. Furthermore, whether or not an additional propylene copolymer is present, the recyclable thermoplastic layer comprising TPV and polyethylene can advantageously include a dielectric liquid, such as a dielectric oil. Advantageously, the recyclable thermoplastic layer of the invention comprises a polar compound such as benzophenone, which further optimizes its dielectric properties. Where appropriate, the benzophenone-type polar compound is advantageously present in the layer at a concentration of 0.1 to 0.5% by mass (for example, between 0.2 and 0.4%, particularly in the range of 0.3% by mass) relative to the total mass of the recyclable thermoplastic layer. Typically, a benzophenone-type polar compound is used in a mixture with a dielectric liquid, in particular a dielectric oil. The polar compound (for example, benzophenone) is then advantageously premixed with said dielectric liquid before its incorporation into the polymer composition forming the thermoplastic layer, this premix forming an additively enhanced dielectric liquid particularly suited to the implementation of the invention. A cable according to the invention is preferably a so-called low voltage type power cable (i.e. intended to carry a current voltage of less than 6kV) or a so-called medium voltage type power cable (which is intended to carry a current voltage between 6 and 60 kV). In the case of a low voltage power cable, the recyclable thermoplastic layer is typically an insulation layer, preferably internal to said cable. In the case of a medium-voltage power cable, the cable may comprise one or more recyclable thermoplastic layers according to the invention, each of said layers being either an insulating layer or a semiconducting layer. In other words, in the case of a medium-voltage power cable, the recyclable thermoplastic layer according to the invention is either an insulating layer or a semiconducting layer. Various aspects and particular embodiments of the invention are described in more detail below. THE COMPOSITE MATERIAL (TPV) Preferably, the TPV material is present in the recyclable thermoplastic layer according to the invention at a rate of 5 to 20% by mass relative to the total mass of said layer. POLYETHYLENE The polyethylene present in the recyclable thermoplastic layer according to the invention may, in particular, be low-density polyethylene, and preferably linear low-density polyethylene, in particular according to ISO 1183A (at a temperature of 23°C). In the present invention, the expression "linear low-density polyethylene" means linear polyethylene having a density ranging from approximately 0.91 to 0.925, said density being measured according to ISO 1183A (at a temperature of 23°C). Whatever its nature, polyethylene is preferably present in the recyclable thermoplastic layer according to the invention at a rate of 15 to 30% by mass relative to the total mass of the mass of said layer. The polyethylene / TPV mass ratio, calculated by the ratio of the total mass of polyethylene in the layer, to the total mass of TPV in the layer, is preferably between 2 and 4, and typically in the range of 2.5 to 3.5, for example 3. PROPYLENE COPOLYMER (c) The propylene copolymer (c) is an optional compound advantageously present in the thermoplastic layer, further improving its performance. This compound (c) is preferably a copolymer of propylene and an alpha olefin distinct from propylene. This alpha olefin, distinct from propylene, is preferably a compound of formula CH,=CH-R, where R is a linear or branched alkyl group comprising 2 to 12 carbon atoms, and it may in particular be chosen from the following alpha-olefins: ethylene, 1-butene, 1-pentene; 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, and one of their mixtures. Whatever its exact nature, the alpha-olefin other than propylene (ethylene or other) present in the copolymer (c) preferably represents less than 15% by mole, for example between 1 and 10% by mole, relative to the total number of moles of monomer units in the propylene and olefin copolymer. DIELECTRIC LIQUID AND BENZOPHENONE-TYPE POLAR COMPOUNDS When a dielectric liquid is present in the thermoplastic layer of the invention, it can advantageously be chosen from mineral oils (for example naphthenic oils, paraffinic oils or aromatic oils), vegetable oils (in particular soybean, linseed, rapeseed, corn, and / or castor oil) or synthetic oils such as aromatic hydrocarbons (alkylbenzenes, alkylnaphthalenes, alkylbiphenyls, alkyldiarylethylenes, etc.), silicone oils, ethers, organic esters or aliphatic hydrocarbons. According to a particular embodiment, the dielectric liquid is present at a level of approximately 0% to 20% by mass, preferably approximately 1% to 10% by mass, and of preferably still 3 to 7% by mass approximately, relative to the total mass of the thermoplastic polymer material layer. The dielectric liquid may advantageously comprise a mineral oil. A mineral oil useful as a dielectric liquid according to the invention is generally liquid at least over the temperature range between 20 and 25°C and advantageously at least over the temperature range between 15°C and 30°C. Examples of mineral oil useful as a dielectric liquid according to the invention include naphthenic oils, paraffinic oils and mineral oils obtained from the refining of crude oil. According to a particularly preferred embodiment of the invention, the mineral oil comprises a paraffinic carbon (Cp) content of approximately 45 to 65 atomic percent, a naphthenic carbon (Cn) content of approximately 35 to 55 atomic percent, and an aromatic carbon (Ca) content of approximately 0.5 to 10 atomic percent. Furthermore, the thermoplastic layer of the invention advantageously comprises at least one polar compound of the benzophenone or acetophenone type, or a derivative thereof. The polar compound may be selected, in particular, from among: benzophenone, acetophenone, dibenzosuberone, fluorenone, and anthrone. Benzophenone is particularly preferred. Advantageously, the dielectric fluid included in the polymer layer of the invention comprises a mixture of a mineral oil, preferably of the type described above. According to this embodiment, the dielectric fluid may advantageously comprise at least approximately 70% by mass of mineral oil, and preferably at least approximately 80% by mass of mineral oil, relative to the total mass of the dielectric fluid. The proportion of polar compound (of the benzophenone or acetophenone type or derivatives thereof) preferably represents at least approximately 2.5% by mass, preferably at least approximately 3.5% by mass, and even more preferably at least approximately 4% by mass, relative to the total mass of the dielectric fluid. OTHER OPTIONAL ADDITIVES The polymer layer of the invention may advantageously include one or more additives other than the aforementioned compounds, for example antioxidants, anti-UV agents, anti-copper agents, anti-water treeing agents, pigments, and mixtures thereof. Power cables comprising a recyclable thermoplastic layer according to the invention A cable incorporating a recyclable thermoplastic layer according to the invention may, in particular, be: - an electrical cable comprising at least one electrically conductive element elongated, surrounded by said recyclable thermoplastic layer, this layer being, for example: - an insulating layer (preferably internal to the cable, or alternatively an external sheath); or - a semiconductor layer DIAPER USED AS AN INSULATING DIAPER When the recyclable thermoplastic layer of the invention is an electrically insulating layer, it preferably has an electrical conductivity of at most 1.10-9 S / m (siemens per meter) at 25°C. DIAPER USED AS A SEMI-CONDUCTIVE DIAPER When the recyclable thermoplastic layer of the invention is a semiconducting layer, it generally comprises an electrically conductive filler in sufficient quantity to render the polymer composition semiconducting. Carbon black can be cited as an example of a well-suited electrically conductive filler. Here, "semiconductor layer" means a layer whose electrical conductivity is at least 1.10° S / m (siemens per meter), preferably at least 1.107 S / m, and generally less than 1.10 S / m (at 25°C). POSSIBLE STRUCTURES FOR A CABLE ACCORDING TO THE INVENTION According to a first possible embodiment, the recyclable thermoplastic layer of the invention can be used in an electrical cable as an insulating layer in direct physical contact with an elongated electrically conductive element. This embodiment is particularly well-suited for low-voltage cables. According to another possible embodiment, the electrical device of the invention is an electrical cable comprising a first semiconductor layer surrounding an elongated electrically conductive element, an electrically insulating layer surrounding said first semiconductor layer, and a second semiconductor layer surrounding said electrically insulating layer, and wherein the recyclable thermoplastic layer of the invention is at least one of these three layers, preferably at least two of said three layers, and preferably all three layers. In this case, it is referred to as a medium-voltage or high-voltage cable. According to the present invention, the elongated electrically conductive element of the electric cable can be a metallic wire or a plurality of metallic wires, twisted or not, in particular made of copper or aluminum, or one of their alloys. INSTALLATION OF A THERMOPLASTIC LAYER ACCORDING TO THE INVENTION The recyclable thermoplastic layer of the invention can be an extruded layer or a molded layer, which can in particular be obtained by extrusion processes. or molding techniques well known to those skilled in the art. The recyclable thermoplastic layer of the invention is preferably an extruded layer. When the electrical device is an accessory for an electrical cable, the cross-linked layer is preferably a molded layer. The invention will be further illustrated by the Figure in the Annex and the illustrative example below. [Fig.1] Fig.1 represents a schematic view of an electrical cable comprising an insulating thermoplastic layer according to the invention. For the sake of clarity, only the essential elements for understanding the invention have been represented schematically, and this without regard to scale. Figure 1 shows an electrical cable 1 which includes a central elongated electrically conductive element 2, in particular made of copper or aluminum. This electrical cable 1 further comprises several layers arranged successively and coaxially around this central elongated electrically conductive element 2, namely: a first semiconducting layer 3 called the "inner semiconducting layer", an electrically insulating layer 4, a second semiconducting layer 5 called the "outer semiconducting layer", a metallic screen 6 for grounding and / or protection, and an outer protective sheath 7. The electrically insulating layer 4 is a recycled thermoplastic layer according to the invention, obtained by extrusion and comprising a TPV composite material; a polyethylene; advantageously a propylene copolymer; and optionally additives of the aforementioned type. Semiconductor layers 3 and 5 are advantageously recycled thermoplastic extruded layers according to the invention comprising a TPV composite material; a polyethylene; advantageously a propylene copolymer ©, optionally additives of the aforementioned type; and an electrically conductive filler (typically a carbon black). The presence of the metallic screen 6 and the outer protective sheath 7 is preferential, but not essential, this cable structure being a standard type structure. Example The following compositions were tested which include a TPV type composite material (commercial product from the Santoprene and OptiPren range based on an EPDM elastomer phase dispersed in a polypropylene matrix); a polyethylene (LLDPE BPD 3642), a propylene and ethylene copolymer (Moplen RP210G), a mineral oil (BNS28), benzophenone (previously mixed with the oil) and an antioxidant additive (Irganox B225). For comparison, control compositions free of polyethylene and co- Several polymers were tested where these compounds were replaced with TPV. For the most part, these compositions did not result in usable formulations because the absence of polyethylene made oil incorporation impossible. Only the Optipren-based control yielded a homogeneous polymer composition. The compositions of the tested formulas are shown in Table 1 above (quantities are given as parts by weight per 100 parts by weight of the total composition). Composition C4 ca c3 Control Moplen 56.6 0 — LLPDE ï 28 [Try | Santoprene 203-40 94 94 94 o4 | Santoprens 203-50 | OptiPren Oil 5.4 Benzophenone 93 Antioxidant 03 Table 1: Composition of the tested compositions The performance of the compositions thus prepared is shown in Table 2 below. Composition CA ca cs Witness Fransiucidal coloring | fransiucide | dansiucide | opaque white — DSC 115 Temperature of RSS SN SES 124147 123 / 146 Vars | fusion (2nd cycle) Temperature of start of fusion {2° | : melting {2° Ï fIBA27 BASF 118 / 135°C | 142°C cycle) ——" Ms. Mechanical Properties TSP {MPa} 3t.2 286 31.2 18.2 ES) Ÿÿ ECO CCS T Measurements after Thermal Aging {after 10 days 81350} Thermo-pressure measurement Index value 3 Fi 3 23 {rs} Mr. Re Cold Elongation 1 Elongation (%} 687 503 694 >=800 Water intake 5 Mass gain RSS SNS G17 Di4 (mglem” Dielectric specioscopy 8; tan t& f110°C 122.405 2440* see 4.18.10+ 2.410 1.83.tü* 41.408 7ec 3.42. 10 2910? 3C 4.97. 10* 8.240* 289.104 Permittivity 119°C FRE] 1.94 9&c 2,22 222 2.20 220 TUC Z25 295 3e&c 2,33 2.33 231 > 13 Table 2: Performance of the tested compositions Notes: "DSC measurement under nitrogen flow, 3 temperature ramp cycles from -20°C to +250°C at a rate of 10°C / min" @) - measured on INSTRON at -250 mm / min — median over 5 ©): the indentation value is expressed as a percentage (9) - measurement at -25°C 6): Measurement taken after 336 hours of treatment at 85°C "6: Max tan (at) 30°C = 4.107 Max tan (at) 90°C = 8.10"

Claims

Claims

1. Electric cable comprising, around at least one conductive element elongated, a recyclable thermoplastic layer comprising at least: - a composite material (TPV) comprising: (a) a thermoplastic polymer matrix; and (b) a vulcanized elastomeric phase, dispersed within said matrix thermoplastic (a); And - polyethylene.

2. An electrical cable according to claim 1, wherein the elastomeric phase dispersed vulcanized (b) comprises a crosslinked elastomer ethylene-propylene-diene (EPDM).

3. An electrical cable according to claim 1 or 2, wherein the thermo- plastic (a) comprises a homopolymer or copolymer of propylene.

4. An electrical cable according to any one of claims 1 to 3, wherein the thermal layer recyclable moplastic further includes a propylene copolymer and an alpha-olefin other than propylene, preferably a co- polymer of propylene and ethylene.

5. An electric cable according to any one of claims 1 to 4, wherein the thermo-layer recyclable plastic further comprises a dielectric liquid.

6. An electrical cable according to one of claims 1 to 5, wherein the thermal layer recyclable moplastic further comprises benzophenone.

7. An electrical cable according to one of claims 1 to 6, wherein the cable is a low voltage power cable.

8. An electrical cable according to claim 7, wherein the thermoplastic layer recyclable is an insulating layer.

9. An electrical cable according to one of claims 1 to 6, wherein the cable is a medium voltage power cable

10. An electrical cable according to claim 9, wherein the thermoplastic layer recyclable is an insulating layer or a semiconducting layer.