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AssigneePirelli Cavi e Sistemi S.p.A.
InventorsEduardo Grizante Redondo, Franco Peruzzotti, Diego Tirelli, Antonio Zaopo, Enrico Albizzati, Luca Castellani
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A flame-retardant composition includes a crystalline propylene homopolymer or copolymer, a copolymer of ethylene with at least one alpha-olefin having from 3 to 12 carbon atoms, and optionally with a diene, the copolymer of ethylene being characterized by a composition distribution index greater than 45%, the index being defined as a weight percentage of copolymer molecules having an alpha-olefin content within 50% of an average total molar content of alpha-olefin, and natural magnesium hydroxide in amounts such as to impart flame-retardant properties. A related cable with self-extinguishing properties includes a conductor and a flame-retardant coating. The flame-retardant coating includes the flame-retardant composition. A related method for manufacturing a cable having improved mechanical properties and enhanced fire resistance includes the steps of preparing a polymer mixture with flame-retardant properties and extruding the mixture on a conductor optionally pre-coated with an insulating layer, in order to obtain a flame-retardant coating.
A cable with self-extinguishing properties, comprising:
A flame-retardant composition, comprising:
A method for manufacturing a cable having improved mechanical properties and enhanced fire resistance, comprising the steps of:
Dependencies are inferred from the claim text.
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Protection against damage caused by extremes of temperature or by flame: using material resistant to flame
Oxides; Hydroxides: of metals
With unsaturated hydrocarbons only containing four or more carbon atoms: with aliphatic 1-olefins containing one carbon-to-carbon double bond
Not modified by chemical after-treatment: ethylene-propylene or ethylene-propylene-diene copolymers
Term ended 10 Jul 2018 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
1. Field of the Invention
The present invention relates to cables, in particular for low-voltage electrical energy distribution or for telecommunications, these cables having low-smoke self-extinguishing properties, and to the flame-retardant compositions used therein.
2. Description of the Related Art
FIG. 1 shows, in a schematic form, the cross-section of a low-voltage electrical cable of unipolar type according to one embodiment of the present invention, this cable comprising a conductor (1), an inner layer (2) acting as electrical insulation and an, outer layer (3) acting as a protective sheath with flame-retardant properties, consisting of the composition according to the present invention.
The term “low voltage” is understood generally to refer to a voltage of less than 2 kV, preferably less than 1 kV.
The inner layer (2) may consist of a halogen-free, crosslinked or non-crosslinked polymer composition with electrically insulating properties which is known in the art, selected, e.g., from: polyolefins (homopolymers or copolymers of different olefins), olefin/ethylenically unsaturated ester copolymers, polyesters, polyethers, polyether/polyester copolymers, and mixtures thereof. Examples of such polymers are: polyethylene (PE), in particular linear low density PE (LLDPE); polypropylene (PP); propylene/ethylene thermoplastic copolymers; ethylene/propylene rubbers (EPR) or ethylene/propylene/diene rubbers (EPDM); natural rubbers; butyl rubbers; ethylene/vinylacetate (EVA) copolymers; ethylene/methylacrylate (EMA) copolymers; ethylene/ethylacrylate (EEA) copolymers; ethylene/butylacrylate (EBA) copolymers; ethylene/alpha-olefin copolymers, and the like. It is also possible to use the same polymer base for the inner layer (2) as well as for the outer layer (3), namely the mixture of (a) and (b) as defined above.
Alternatively, a self-extinguishing cable according to the present invention may consist of a conductor coated directly with the flame-retardant composition described above, without interposing other insulating layers. In this way, the flame-retardant coating also acts as electrical insulator. A thin polymer layer acting as an anti-abrasive can then be externally added, optionally supplemented with a suitable pigment to colour the cable for identification purposes.