Energy cable having a cold-strippable semiconductive layer

Patent metadata

Field	Value
Publication number	US-10217544-B2
Application number	US-201415536515-A
Country	US
Kind code	B2
Filing date	Dec 17, 2014
Priority date	Dec 17, 2014
Publication date	Feb 26, 2019
Grant date	Feb 26, 2019

Abstract

Energy cable comprising, from the interior to the exterior, an electrical conductor, an inner semiconductive layer, an electrically insulating layer made from a thermoplastic material in admixture with a dielectric fluid, and an outer semiconductive layer, wherein the outer semiconductive layer comprises: (i) from 55 wt % to 90 wt % of a copolymer of ethylene with at least one ester comonomer having an ethylenic unsaturation; (ii) from 10 wt % to 45 wt % of a propylene copolymer with at least one olefin comonomer selected from ethylene and an α-olefin other than propylene, said copolymer having a melting point of from 145° C. to 170° C. and a melting enthalpy of from 40 J/g to 80 J/g; (iii) at least one conductive filler; (iv) at least one dielectric fluid; the amounts of (i) and (ii) being expressed with respect to the total weight of the polymeric components of the layer. The outer semiconductive layer is cold-strippable, having an adhesion with the underlying thermoplastic insulating layer which can be tuned so as to obtain a suitable balance between strippability at a temperature ranging from about 0° C. to about 40° C., without applying heat, and stable adhesion with the insulating layer during the cable lifespan.

First claim

The invention claimed is:

1. An energy cable comprising, from the interior to the exterior, an electrical conductor, an inner semiconductive layer, an electrically insulating layer made from a thermoplastic material in admixture with a dielectric fluid, and an outer semiconductive layer, wherein the outer semiconductive layer comprises:
(i) from 55 wt % to 90 wt % of at least one copolymer of ethylene with at least one ester comonomer having an ethylenic unsaturation;
(ii) from 10 wt % to 45 wt % of a copolymer of propylene with at least one olefin comonomer selected from ethylene and an α-olefin other than propylene, said copolymer having a melting point of from 145° C. to 170° C. and a melting enthalpy of from 40 J/g to 80 J/g;
(iii) at least one conductive filler;
(iv) at least one dielectric fluid;
the amounts of (i) and (ii) being expressed with respect to the total weight of the polymeric components of the layer.

2. Energy cable according to claim 1 , wherein the ethylene copolymer (i) is selected from copolymers of ethylene with at least one ester comonomer selected from: C 1 -C 8 alkyl acrylates, C 1 -C 8 alkyl methacrylates, and vinyl C 2 -C 8 carboxylates.

3. Energy cable according to claim 1 , wherein the ester comonomer is present in the copolymer (i) in an amount of from 10 wt % to 50 wt %.

4. Energy cable according to claim 1 , wherein the ethylene copolymer (i) is selected from: ethylene-vinylacetate copolymers and ethylene-n-butylacrylate copolymers.

5. Energy cable according to claim 1 , wherein the ethylene copolymer (i) is present in an amount of from 60 wt % to 80 wt %.

6. Energy cable according to claim 1 , wherein the ethylene copolymer (i) has a melt flow rate (MFR) of from 0.5 to 10 g/10 min (190° C., 2.16 kg according to ASTM D1238 or ISO 1133).

7. Energy cable according to claim 1 , wherein the propylene copolymer (ii) is present in the outer semiconductive layer in an amount of from 20 wt % to 40 wt %.

8. Energy cable according to claim 1 , wherein the propylene copolymer (ii) has a melting point of from 145° C. to 160° C.

9. Energy cable according to claim 1 , wherein the propylene copolymer (ii) has a melting enthalpy of from 50 to 70 J/g.

10. Energy cable according to claim 1 , wherein the propylene copolymer (ii) contains a crystalline phase in an amount of from 80 wt % to 95 wt % with respect to the weight of the propylene copolymer (ii).

11. Energy cable according to claim 1 , wherein the propylene copolymer (ii) is a mixture of:
(iia) a propylene copolymer having a melting enthalpy of from 50 to 90 J/g; and
(iib) a heterophasic propylene copolymer having a melting enthalpy up to 35 J/g and comprising an elastomeric phase in an amount equal to or greater than 30 wt % with respect to the total weight of the copolymer (iib).

12. Energy cable according to claim 11 , wherein the propylene copolymer (iia) is a random propylene copolymer.

13. Energy cable according to claim 11 , wherein the mixture of (iia) and (iib) contains from 35 to 85 wt % of the propylene copolymer (iia) and from 15 to 65 wt %, of the heterophasic propylene copolymer (iib), the percentages being expressed with respect to the total weight of (iia) and (iib).

14. Energy cable according to claim 11 , wherein the mixture of (iia) and (iib) contains from 40 to 80 wt % of the propylene copolymer (iia) and from 20 to 60 wt % of the heterophasic propylene copolymer (iib), the percentages being expressed with respect to the total weight of (iia) and (iib).

15. Energy cable according to claim 1 , wherein the weight ratio between the at least one dielectric fluid (iv) and the total weight of the copolymers (i) and (ii) may be from 2:98 to 15:85.

Assignees

• Prysmian Spa

Inventors

• Caimi Luigi
• Crisci Vincenzo
• Bareggi Alberto

Classifications

• H01B3/447

  from acrylic compounds · CPC title

• C08L2205/025

  containing two or more polymers of the same hierarchy C08L, and differing only in parameters such as density, comonomer content, molecular weight, structure · CPC title

• C08L23/08

  Copolymers of ethene (C08L23/16 takes precedence) · CPC title

• C08L23/0853 Primary

  Ethylene vinyl acetate copolymers · CPC title

• C08L2207/02

  Heterophasic composition · CPC title