Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2001-06-28
2003-08-26
Kelly, Cynthia H. (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S375000, C174S1100PM, C174S1100SR, C174S1200SR
Reexamination Certificate
active
06610401
ABSTRACT:
The present invention relates to cables, in particular for medium-voltage or high-voltage electrical power transmission or distribution, for telecommunications or for data transmission, as well as combined power/telecommunications cables, in which at least one coating layer consists of a halogen-free recyclable material which has high-performance mechanical and electrical properties. There is currently a great need for products which are highly environment-friendly, formed of materials which are not only harmless to the environment both during production and during use, but are also easy to recycle at the end of their life. However, the use of environment-friendly materials is highly conditioned by the requirements for keeping their costs within acceptable limits and at the same time ensuring satisfactory performance levels under the most common conditions of use, or even better performance than those of conventional materials. in the cables sector, in particular medium-voltage or high-voltage electrical power transmission or distribution cables, the various coatings which surround the conductor usually consist of crosslinked polymer material, in particular of polyethylene or ethylene copolymers suitably crosslinked during the extrusion phase. The reason for this is that these crosslinked materials maintain a high degree of flexibility and satisfactory mechanical properties even under hot conditions in continuous use and/or under conditions of current overload. However, it is well known that crosslinked materials are not recyclable and that, at the end of their life, they can only be disposed of by incineration. In addition, in certain cases the outer protective sheath is formed of polyvinyl chloride (PVC) which is difficulty to separate by conventional methods (for example by density differences in water)—from crosslinked polyolefins containing inorganic fillers (for example ethylene/propylene rubbers containing inorganic fillers), nor can it be incinerated just as it is, by combustion, since this generates highly toxic chlorinated products.
Patent application WO 96/23311 describes a low-voltage high-current cable in which the insulating coating, the inner sheath and the outer sheath are made of the same non-crosslinked polymer material which is coloured black by the addition of carbon black. Using the same material would not require the separation of the abovementioned components in a recycling process. When temperatures below 70° C. are used, a polyethylene with a density of between 0.92 and 0.94 g/cm
2
and a Shore D hardness ≧42 is proposed as polymer material for the insulating coating, the inner sheath and the outer sheath. The use of thermoplastic elastomers consisting of two-phase mixtures of polypropylene with an ethylene/propylene co- or terpolymer (EPR or EPDM rubber) is proposed in the case of a maximum working temperature of 90° C. Within the latter class of polymers, mention is specifically made of the commercial products Santoprene® from Monsanto (polypropylene-based thermoplastic elastomer) and Novolen® from BASF (heterogeneous propylene copolymers obtained in a reactor and having an ethylene/propylene elastomeric phase content of greater than 25% by weight, for example 43% by weight of ethylene/propylene rubber, such as Novolen® 2912 HX from BASF). The Applicant has observed that the technical problem of obtaining a recyclable polymer material for coating electrical cables, in particular medium- or high-voltage cables, which has the desired combination of electrical and mechanical properties can be solved by using a heterogeneous copolymer comprising an ethylene-based elastomeric phase copolymerized with an &agr;-olefin and a propylene-based thermoplastic phase, characterized in that the elastomeric phase is at least 45% by weight relative to the total weight of the heterogeneous copolymer and in that this copolymer is essentially free of crystallinity deriving from polyethylene sequences. In point of fact, it has been suggested that a large amount of elastomeric phase combined with a substantial absence of crystalline polyethylenic sequences gives, on the one hand, the desired mechanical properties for an electrical cable, and in particular a breaking load value of greater than 12 MPa (measured according to CEI standard 20-34 § 5.1), and, on the other hand, excellent electrical insulation properties, in particular low dielectric losses, even under hot conditions and in particular at the maximum working temperature of the cable, with values for the tangent of the angle of loss (tan delta) at 90° C. (measured according to ASTM standard D150) of less than 5×10
4
. In a first aspect thereof, the present invention thus relates to a cable comprising a conductor and at least one coating layer based on a non-crosslinked polymer material comprising a heterogeneous copolymer with an ethylene-based elastomeric phase copolymerized with an &agr;-olefin and a propylene-based thermoplastic phase, characterized in that the said elastomeric phase in the said heterogeneous copolymer is at least 45% by weight relative to the total weight of the heterogeneous copolymer, and in that the said heterogeneous copolymer is essentially free of crystallinity deriving from polyethylene sequences.
According to another aspect, the invention relates to a cable comprising a conductor and at least one coating layer, in which the said coating layer has electrical insulating properties and is based on a non-crosslinked polymer material comprising a heterogeneous copolymer as defined above.
According to a further aspect, the invention relates to a cable comprising a conductor and at least one coating layer, in which the said coating layer has semiconductive properties and is based on a non-crosslinked polymer material comprising a heterogeneous copolymer as defined above.
According to a further aspect, the invention relates to a cable comprising a conductor and at least one coating layer, in which the said coating layer functions as an outer protective sheath and is based on a non-crosslinked polymer material comprising a heterogeneous copolymer as defined above.
According to a further aspect, the invention relates to a cable comprising a conductor and at least one coating layer based on a non-crosslinked polymer material, in which at least 70%, preferably at least 90%, by weight of the said non-crosslinked polymer material consists of a heterogeneous copolymer as defined above.
For the purposes of the present description and the claims which follow, the expression “heterogeneous copolymer comprising an ethylene-based elastomeric phase copolymerized with an &agr;-olefin and a propylene-based thermoplastic phase” means a thermoplastic elastomer obtained by sequential copolymerization of: (a) propylene, optionally containing small amounts of at least one olefinic comonomer chosen from ethylene and &agr;-olefins other than propylene; and then: (b) a mixture of ethylene with an &agr;-olefin, in particular propylene, and optionally with small proportions of a diene. This class of products is also commonly known as “thermoplastic reactor elastomers”.
Throughout the present description and the claims which follow, the expression “heterogeneous copolymer essentially free of crystallinity deriving from polyethylenic sequences” means that the heterogeneous copolymer subjected to differential scanning calorimetry (DSC) analysis does not show any appreciable melting peaks attributable to a crystalline polyethylenic phase, i.e. to (CH
2
)
n
sequences of crystalline type. In quantitative terms, this means that the value of the enthalpy of fusion of peaks present below 130° C. and attributable to polyethylenic sequences is generally less than 3 J/g: preferably, it is substantially zero.
Alternatively, the substantial absence of crystallinity due to polyethylenic sequences can be ascertained by extraction of the elastomeric (amorphous) phase by means of a suitable organic solvent (for example xylene at 135° C. at reflux for 20 min.) and analysis of the residue formed by the crystalline phase, for ex
Albizzati Enrico
Castellani Luca
Scelza Cristiana
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Gray J. M.
Kelly Cynthia H.
Pirelli Cavi e Sistemi S.p.A.
LandOfFree
Cables with a recyclable coating does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cables with a recyclable coating, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cables with a recyclable coating will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3126140