Cable or cable accessory comprising a fire-resistant layer

Abstract

The invention relates to a device comprising a cable and/or a cable accessory, said cable and/or cable accessory containing at least one insulating and fire-resistant layer, as well as to a method for manufacturing a cable and/or accessory of said type.

Claims

1. A device comprising: a power cable and/or telecommunications cable and/or a cable accessory, wherein said cable and/or said cable accessory has at least one fire-resistant insulating layer based on a composite material having at least one cementing material representing from 5 to 95 wt % relative to the total weight of the composite material and at least one nonwoven fibrous material of pliable and flexible structure, and in that said layer is an inner layer of said cable or of said cable accessory.

2. The device as claimed in claim 1, wherein the cementing material is a solid material comprising silicon (Si), aluminum (Al), phosphate (P), oxygen (O) and at least one element selected from potassium (K), sodium (Na), lithium (Li), cesium (Cs) and calcium (Ca), said solid material being a geopolymer cement or being obtained from a mixture made of an anhydrous cement and water.

3. The device as claimed in claim 1, wherein the layer of composite material has a thickness ranging from 0.2 to 10 mm.

4. The device as claimed claim 1, wherein the cementing material is an aluminosilicate geopolymer cement.

5. The device according to claim 1, wherein the geopolymer cement is selected from the compounds in which the Si/Al molar ratio varies from 1.9 to 3.

6. The device according to claim 1, wherein the anhydrous cement is white cement or slag and ash cement.

7. The device according to claim 1, wherein the cementing material represents from 70 to 90 wt % relative to the total weight of the composite material.

8. The device according to claim 1, wherein the nonwoven fibrous material is selected from paper, glass fibers, nonwoven materials manufactured from functionalized or nonfunctionalized cellulose, cellular polypropylene matrixes and matrixes with a cellular and/or fibrous structure manufactured from natural cellulose acetate fibers.

9. The device according to claim 1, wherein the fibrous material is in the form of strip or tape.

10. The device according to claim 1, wherein the fibrous material represents from 5 to 95 wt % relative to the total weight of the composite material.

11. The device according to claim 1, wherein the composite material further comprises at least one organic additive with a polymer structure.

12. The device as claimed in claim 11, wherein the polymer additive is selected from polypropylene, the styrene-butadiene copolymers; styrene-butadiene-ethylene copolymers; derivatives of styrene-ethylene copolymers; copolymers of ethylene and vinyl acetate, crosslinked polyorganosiloxanes; polyethylene; lignosulfonates; cellulose and derivatives thereof; and a mixture thereof.

13. The device as claimed in claim 11, wherein the polymer additive represents from 2 to 70 wt %, relative to the total weight of the composite material.

14. The device according to claim 1, wherein the layer comprising at least one cementing material further comprises one or more agents that retard setting of the cement composition at room temperature.

15. The device as claimed in claim 14, wherein the retarder is selected from the lignosulfonates.

16. The device as claimed in claim 14, wherein the retarder represents from 5 to 60 wt %, relative to the total weight of the composite material.

17. A method for manufacturing a device that has a power cable and/or a telecommunications cable and/or a cable accessory as defined in claim 1, said device having at least one fire-resistant insulating layer based on a composite material having at least one cementing material representing from 5 to 95 wt % relative to the total weight of the composite material and at least one nonwoven fibrous material of pliable and flexible structure, and optionally at least one polymer additive, said method comprising the steps of: i) a step of preparing a cement composition comprising: at least one geopolymer composition or at least one mixture consisting of an anhydrous cement and water, and optionally at least one polymer additive; ii) a step of applying a nonwoven fibrous material of pliable and flexible structure: either around one or more elongated conductors or around an inner layer of a power cable and/or telecommunications cable when the device is a cable, to obtain a cable/fibrous material assembly, or around at least one of the inner layers of a joint or of a termination when the device is a cable accessory; to obtain a cable accessory/fibrous material assembly; iii) a step of impregnating the cable/fibrous material or cable accessory/fibrous material assembly obtained above in the preceding step with said geopolymer composition; iv) a step of hardening the geopolymer composition or mixture consisting of a conventional anhydrous cement and water impregnating said fibrous material, to form a fire-resistant insulating layer based on said composite material.

18. The method as claimed in claim 17, wherein the geopolymer composition in step i) is an aluminosilicate geopolymer composition having the following molar composition (I):
w SiO.sub.2:x Al.sub.2O.sub.3:y M.sub.2O:z H.sub.2O   (I) in which: M is selected from Na, K, Li, Cs and a mixture thereof, w is a value between about 0.1 and 8, x is a value between about 0.1 and 0.3, y is a value between about 0.05 and 0.2, z is a value between about 0.8 and 3, said composition having from 40 to 79 wt % of solid materials relative to the total weight of said composition.

19. The method as claimed in claim 18, having the solids/water weight ratio in said geopolymer composition varies from 0.6 to 1.65.

20. The method as claimed in claim 18, wherein step i) comprises the following substeps: i.sub.1) a step of preparing an aqueous solution of alkaline silicate of SiO.sub.2/M.sub.2O molar ratio ranging from 1.65 to 3.4, the concentration by weight of the alkaline silicate in water ranging from 35 to 90%, and i.sub.2) a step of mixing an aluminosilicate in the form of powder, with Al.sub.2O.sub.3/SiO.sub.2 molar ratio ranging from 0.4 to 0.8, with the aqueous solution of alkaline silicate prepared in the preceding step, where the concentration by weight of the aluminosilicate in the aqueous solution of alkaline silicate prepared in the preceding step may vary from 10 to 80%.

21. The method as claimed in claim 17, wherein the device is a power cable or a transmission cable, and in that the nonwoven fibrous material of pliable and flexible structure is in the form of tape or strip and step ii) of application of said fibrous material is then carried out by winding said tape or said strip around one or more elongated conductors or around an inner layer of said cable, where said winding may moreover be carried out with overlaps.

22. The method as claimed in claim 17, wherein the device is a power cable or a transmission cable, and in that the method further comprises an additional step, before, during or after step iv), of making an insulating protective sheath around the layer made of said fibrous material impregnated with the cement composition.

Description

EXAMPLES

[0102] The raw materials used in the examples are listed below: [0103] Sodium silicate of the “waterglass” type, Simal, of formula Na.sub.2O.2SiO.sub.2, with SiO.sub.2/Na.sub.2O molar ratio of about 2, [0104] Running water, [0105] Potassium hydroxide, Sigma Aldrich, of purity >85%, [0106] Aluminosilicate sold under the trade name PoleStar® 200R, by the company Imérys, with Al.sub.2O.sub.3/SiO.sub.2 molar ratio of 41/55 (i.e. about 0.745), [0107] Polypropylene fibers sold under the trade name CELLOTIN PP6 by the company ZSCHIMMER & SCHWARZ.

[0108] Unless stated otherwise, all these raw materials were used as received from the manufacturers.

Example 1: Manufacture of a Fire-Resistant Cable According to the Invention

1.1. Preparation of a Geopolymer Composition (Step i)

[0109] A solution of alkaline silicate was prepared by mixing 36 g of sodium silicate, 20 g of water and 8 g of potassium hydroxide. Then 39 g of aluminosilicate and 2.2 g of polypropylene fibers were mixed with the aqueous solution of alkaline silicate.

[0110] Said composition had a solids content of about 80 wt %. It was used immediately in the next step.

1.2. Manufacture of a Fire-Resistant Cable

[0111] Two cable designs were assessed: [0112] an assembly of 2 copper conductors each having a cross section of 1.5 mm.sup.2, designated Assembly 1; [0113] an assembly of 4 copper conductors each having a cross section of 1.5 mm.sup.2, designated Assembly 2.

[0114] The conductors were assembled according to a defined pairing pitch. Nonwoven paper tape having a thickness of 0.2 mm and a width of 30 mm was wound or laid lengthwise around each of the assemblies 1 and 2.

[0115] Each of the assemblies 1 and 2 was then impregnated by dip coating in the geopolymer composition prepared above in the preceding step.

[0116] Each of the assemblies 1 and 2 was then covered by hot extrusion with a protective polymer sheath based on a mixture of linear low-density polyethylene (LLDPE) and EVA and comprising 63 wt % of inorganic fireproofing fillers (alumina trihydrate (ATH) and CaCO.sub.3) having a thickness of 1.03 mm. Power cables were thus obtained, CE1 and CE2 respectively, comprising a fire-resistant layer based on a composite material as defined in the first object of the invention.

1.3. Cable Performance

[0117] The cables CE1 and CE2 thus obtained were evaluated with respect to their fire resistance performance. The assembly was placed in a furnace and exposed to a temperature close to 1000° C. for a period varying from 30 min to 2 hours (standard DIN 4102-12).

[0118] The cables CE1 and CE2 were also tested for their flame resistance performance by the method recommended by standard EN 50200, i.e. by directly exposing the cables CE1 and CE2 to the flame of a propane burner, giving a constant temperature of nominal theoretical attack of 842° C.

[0119] The cables according to the invention gave a fire resistance of 90 min (E90) according to standard DIN 4102-12 and of 121 minutes according to standard EN 50200.

[0120] For comparison, a cable not according to the invention (CE3), prepared by an identical method, but not comprising a layer of composite material based on the geopolymer composition, was also tested with respect to its fire resistance performance according to standard DIN 4102-12. The cable CE3 showed a fire resistance of only 31 min.

[0121] For comparison, another cable not according to the invention (CE4), prepared by an identical method, but in which the layer of composite material based on the geopolymer composition was replaced with aluminum tape with a thickness of 25 μm, was also tested with respect to its flame resistance performance according to standard EN 50200. The cable CE4 showed a fire resistance of only 17 min.

[0122] Consequently, these tests demonstrate that the presence of the layer of composite material makes it possible to improve the fire resistance and flame resistance of the cables very significantly.