Impact-resistant self-extinguishing cable

• US 7,049,524 B2
• Filed: 02/20/2001
• Issued: 05/23/2006
• Est. Priority Date: 02/21/2000
• Status: Expired due to Term

• Current Assignee: Prysmian Cavi E Sistemi Italia Srl (Prysmian SPA)
• Original Assignee: Pirelli Cavi e Sistemi S.P.A. (Prysmian SPA)
• Inventors: Belli, Sergio, Tirelli, Diego, Bareggi, Alberto, Veggetti, Paolo
• Primary Examiner(s): Mayo, III, William H.
• Application Number:
  US10/203,834
• Publication Number:
  US 20030141097A1
• Time in Patent Office: 1,918 Days
• Field of Search: 174/110.R, 174/110.SR, 174/110.N, 174/110.D, 174/110.FC, 174/110.S, 174/110.F, 174/113.R, 174/116, 174/120.R, 174/121.R, 174/121.A
• US Class Current: 174/120.00R
• CPC Class Codes: H01B 3/441 from alkenes
• CPC Class Codes: H01B 7/295 using material resistant to flame

Abstract

Self-extinguishing cable, in particular an electrical cable for low-voltage or medium-voltage power transmission or distribution of data transmission, having at least one conductor and at least one flame-retardant coating positioned externally to the conductor. The flame-retardant coating is produced from an expanded polymeric material which incorporates at least one intumescent agent.

Claims

1. A self-extinguishing cable, comprising:

at least one conductor and at least one flame-retardant coating in a position radially external to said at least one conductor, said at least one flame-retardant coating comprising an expanded polymeric material which incorporates at least one intumescent agent, wherein the thickness of said at least one flame-retardant coating is between 0.5 mm and 6 mm.

2. A self-extinguishing cable according to claim 1, wherein said cable comprises a polymeric sheath in a position radially external to said at least one flame-retardant coating.

3. A self-extinguishing cable according to claim 1, wherein said at least one intumescent agent comprises at least one phosphorus-containing compound.

4. A self-extinguishing cable according to claim 3, wherein said at least one phosphorus-containing compound is chosen from the group:

phosphorous acid salts, phosphoric acid salts, organic esters of phosphoric acid, organic polyesters of phosphoric acid, and mixtures thereof.

5. A self-extinguishing cable according to claim 1, wherein said at least one intumescent agent comprises at least one nitrogen-containing compound.

6. A self-extinguishing cable according to claim 5, wherein said at least one nitrogen-containing compound is chosen from the group:

ammonium salts, melamine, guanidine, melamine cyanurate, guanidylurea, urea and mixtures thereof.

7. A self-extinguishing cable according to claim 1, wherein said at least one intumescent agent comprises compounds containing both phosphorus and nitrogen.

8. A self-extinguishing cable according to claim 7, wherein said compounds are chosen from:

phosphates, polyphosphates or pyrophosphates of ammonia, of guanidine, of melamine or of piperazine;

phosphoramides, phosphorylamides, amidophosphonates, phosphonitrile compounds, and mixtures thereof.

9. A self-extinguishing cable according to claim 1, wherein said polymeric material is a polyolefinic polymer or copolymer based on ethylene and/or propylene.

10. A self-extinguishing cable according to claim 9, wherein said polymeric material is chosen from

a) copolymers of ethylene with an ethylenically unsaturated ester, in which the amount of unsaturated ester is between 5% and 80% by weight;

b) elastomeric copolymers of ethylene with at least one C₃–

C₁₂ α

-olefin, and optionally a diene, having the following composition;

35 mol % to 90 mol % of ethylene, 10 mol % to 65 mol % of α

-olefin, 0 mol % to 10 mol % of diene;

c) copolymers of ethylene with at least one C₄–

C₁₂ α

-olefin, and optionally a diene, generally having a density of between 0.86 and 0.90 g/cm³; and

d) polypropylene modified with ethylene/C₃–

C₁₂ α

-olefin copolymers, in which the weight ratio between the polypropylene and the ethylene/C₀₃–

C₁₂ α

-olefin copolymer is between 90/10 and 30/70.

11. A self-extinguishing cable according to claim 10, wherein the amount of unsaturated ester of said a) copolymers of ethylene with an ethylenically unsaturated ester is between 10% and 50% by weight.

12. A self-extinguishing cable according to claim 10, wherein the weight ratio between the polypropylene and the ethylene/C₃–

C₁₂ α

-olefin copolymer of said d) polypropylene modified with ethylene/C₃–

C₁₂ α

-olefin copolymers is between 50/50 and 30/70.

13. A self-extinguishing cable according to claim 1, wherein the expansion degree of said at least one flame-retardant coating is between 5% and 500%.

14. A self-extinguishing cable according to claim 13, wherein said expansion degree is between 10% and 200%.

15. A self-extinguishing cable according to claim 14, wherein said expansion degree is between 20% and 150%.

16. A self-extinguishing cable according to claim 1, wherein said thickness is between 1 mm and 4 mm.

17. A self-extinguishing cable according to claim 1, wherein the amount of said at least one intumescent agent is between 1% and 60% by weight relative to the total weight of the base composition.

18. A self-extinguishing cable according to claim 17, wherein said amount is between 2% and 50% by weight.

19. A self-extinguishing cable according to claim 18, wherein said amount is between 5% and 30% by weight.

20. A self-extinguishing cable according to claim 1, wherein said expanded polymeric material incorporates at least one mineral-filler.

21. A self-extinguishing cable according to claim 20, wherein the amount of said at least one mineral filler is not greater than 60 phr.

22. A self-extinguishing cable according to claim 20, wherein said at least one mineral filler is a flame-retardant filler.

23. A self-extinguishing cable according to claim 22, wherein said flame-retardant filler is chosen from the group:

magnesium hydroxide, alumina trihydrate, magnesium hydrated carbonate, magnesium carbonate, mixed hydrated carbonate of magnesium and calcium, mixed carbonate of magnesium and calcium, and mixtures thereof.

24. A self-extinguishing cable according to claim 20, wherein said at least one mineral filler is an inorganic substance chosen from:

glass fibres, calcinated kaolin, calcium carbonate and mixtures thereof.

25. A self-extinguishing cable according to claim 1, wherein said at least one flame-retardant coating satisfies the flame-resistance characteristics according to IEC standard 332/3C (second edition, 1992-03).

26. A self-extinguishing cable according to claim 1, wherein said at least one flame-retardant coating is obtained by extrusion.

27. A self-extinguishing cable according to claim 26, wherein expansion of said at least one flame-retardant coating is carried out during said extrusion by adding an expanding agent.

28. A self-extinguishing cable according to claim 27, wherein said expansion is obtained by injecting a gas at high pressure.

29. A self-extinguishing cable according to claim 27, wherein, after expansion, said polymeric material is subjected to crosslinking.

30. A method for imparting flame retardant and impact-resistance properties to a cable, comprising:

applying to said cable at least one flame-retardant coating comprising an expanded polymeric material, which incorporates at least one intumescent agent, wherein the thickness of said at least one flame-retardant coating is between 0.5 mm and 6 mm.

31. A method according to claim 30, wherein said at least one flame-retardant coating is obtained by extrusion.

32. A self-extinguishing cable comprising:

at least one conductor, an electrical insulation in a position radially external to said at least one conductor and at least one flame-retardant coating in a position radially external to said electrical insulation, said at least one flame-retardant coating comprising an expanded polymeric material which incorporates at least one intumescent agent;

wherein the thickness of said at least one flame-retardant coating is between 0.5 mm and 6 mm.