Device comprising a cable or a cable accessory containing a fire-resistant composite layer

Abstract

The present invention relates to a device comprising a cable and/or a cable accessory, said cable and/or said cable accessory comprising at least one composite layer obtained from a composite composition based on at least one cellulose derivative, at least one organic compound having a boiling point or a decomposition temperature above about 100 C. and at least one cement composition selected from an aluminosilicate geopolymer composition and a magnesium-based composition, as well as to a method of manufacturing such a device.

Claims

1. A device comprising: a power cable and/or a telecommunication cable, and/or an accessory for a power cable and/or a telecommunication cable, wherein said cable and/or said cable accessory comprise at least one composite layer obtained from a composite composition comprising at least one organic compound having a boiling point or a decomposition temperature above 100 C., at least one cellulose derivative, and at least one cement composition selected from the group consisting of an aluminosilicate geopolymer composition, and a magnesium-based composition, said magnesium-based composition comprising a magnesium silicate, an alkaline silicate, water, and an alkaline base, and wherein the organic compound represents from 10 to 70 wt %, relative to the total weight of the composite composition.

2. The device according to claim 1, wherein the cement composition is selected from the group consisting of: the aluminosilicate geopolymer composition, and the magnesium-based composition, said cement composition comprising water, silicon (Si), aluminium (Al) or magnesium (Mg), oxygen (O), and at least one element selected from potassium (K), sodium (Na), lithium (Li), caesium (Cs), and calcium (Ca).

3. The device according to claim 1, wherein the aluminosilicate geopolymer composition comprises an alkaline silicate, an aluminosilicate, water, and optionally an alkaline base.

4. The device according to claim 1, wherein the aluminosilicate geopolymer composition comprises from 10 to 50 wt % of an aluminosilicate, from 8 to 35 wt % of an alkaline silicate, from 0 to 10 wt % of an alkaline base and from 10 to 55 wt % of water.

5. The device according to claim 1, wherein the magnesium-based composition comprises from 10 to 50 wt % of the magnesium silicate, from 8 to 35 wt % of the alkaline silicate, from 5 to 20 wt % of the alkaline base and from 10 to 55 wt % of water.

6. The device according to claim 1, wherein the cement composition represents from 10 to 80 wt %, relative to the total weight of the composite composition.

7. The device according to claim 1, wherein the cellulose derivative is a cellulose ether or a cellulose ester.

8. The device according to claim 1, wherein the cellulose derivative represents from 1 to 25 wt %, relative to the total weight of the composite composition.

9. The device according to claim 1, wherein the organic compound is selected from polyols.

10. The device according to claim 1, wherein the composite composition further comprises an expanded carbon-containing material.

11. The device according to claim 1, wherein the composite composition further comprises one or more additives selected from starch, a plasticizer, an inert filler, a dye, an organic additive with a polymer structure, a crosslinking agent and a mixture thereof.

12. The device according to claim 1, wherein the composite layer is in the form of an extruded layer and/or a taped layer, or a layer in the form of a filling.

13. The device according to claim 1, wherein the composite layer has a thickness ranging from 2 to 6 mm.

14. The device according to claim 1, wherein the composite layer is an inner layer of said cable or of said cable accessory.

15. A composite composition for a composite layer of a power cable and/or a telecommunication cable, or an accessory for a power cable and/or a telecommunication, said composite composition comprising: at least one organic compound having a boiling point or a decomposition temperature above 100 C., at least one cellulose derivative, and at least one cement composition selected from the group consisting of; an aluminosilicate geopolymer composition and a magnesium-based composition, said magnesium-based composition comprising a magnesium silicate, an alkaline silicate, water, and an alkaline base, and wherein the organic compound represents from 10 to 70 wt %, relative to the total weight of the composite composition.

16. A device comprising a power cable and/or a telecommunication cable, and/or an accessory for a power cable and/or a telecommunication cable, wherein said cable and/or said cable accessory comprise at least one composite layer obtained from a composite composition comprising at least one organic compound having a boiling point or a decomposition temperature above 100 C., at least one cellulose derivative, and at least one cement composition selected in the group consisting of: an aluminosilicate geopolymer composition, and a magnesium-based composition, said magnesium-based composition comprising a magnesium silicate, an alkaline silicate, water, and an alkaline base, and wherein the composite composition further comprises an expanded carbon-containing material.

17. A device comprising a power cable and/or a telecommunication cable, and/or an accessory for a power cable and/or a telecommunication cable, wherein said cable and/or said cable accessory comprise at least one composite layer obtained from a composite composition comprising at least one organic compound having a boiling point or a decomposition temperature above 100 C., at least one cellulose derivative, and at least one cement composition, wherein said cement composition is a magnesium-based composition comprising from 10 to 50 wt % of a magnesium silicate, from 8 to 35 wt % of an alkaline silicate, from 5 to 20 wt % of an alkaline base and from 10 to 55 wt % of water.

18. Method of manufacturing a device as defined in claim 1, wherein said method comprises at least the following steps: 1) preparing a composite composition according to at least the following steps: i) preparing a cement composition selected from an aluminosilicate geopolymer composition comprising an aluminosilicate, an alkaline silicate, water, and optionally an alkaline base, and a magnesium-based composition comprising a magnesium silicate, an alkaline silicate, water, and an alkaline base, ii) mixing the cement composition from step i) with a cellulose derivative, an organic compound having a boiling point or a decomposition temperature above about 100 C., and optionally water, wherein the organic compound represents from 10 to 70 wt %, relative to the total weight of the composite composition; and 2) forming a composite layer starting from the composite composition obtained in step 1): either around one or more elongated conducting elements and/or around a layer of a power cable and/or telecommunication cable, when the device is a cable, or around at least one of the layers of a junction or of a termination, when the device is a cable accessory.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be better understood, and other aims, details, features and advantages of the invention will become clearer from the following description of particular embodiments of the invention, given solely for purposes of illustration and non-limiting, referring to the appended figures.

(2) In these figures:

(3) FIG. 1 is a schematic view of a cross-section of an electric cable of the prior art not according to the invention;

(4) FIG. 2 is a schematic view of a cross-section of an electric cable according to an embodiment of the present invention.

DETAILED DESCRIPTION

(5) For reasons of clarity, only the elements that are essential for understanding the invention are shown schematically in these figures, which are not to scale.

(6) The electric cable 10, illustrated in FIG. 1, corresponds to a fire-resistant medium-voltage electric cable of type SHXCHX for marine applications.

(7) This electric cable 10 comprises: an elongated central electrically conducting element 1 and, successively and coaxially around this central conducting element 1, an inner semi-conducting screen 1.1, an electrically insulating layer 2 (e.g. of crosslinked ethylene-propylene elastomer, EPR), an outer semi-conducting screen 2.1, a semi-conducting taped layer 3, metal braiding 4 (e.g. consisting of tinned copper wires of circular cross-section), an inner sheath comprising a polyester tape 5 and tinned copper wires 6, a polyester tape 7, and an outer sheath 8 (e.g. of elastomer).

(8) The electric cable 11, illustrated in FIG. 2, corresponds to an electric cable with a structure similar to that of the cable in FIG. 1 but in which two composite layers as defined in the invention have been incorporated.

(9) This electric cable 11 comprises: an elongated central electrically conducting element 1 and, successively and coaxially around this central conducting element 1, an inner semi-conducting screen 1.1, an electrically insulating layer 2 (e.g. of crosslinked ethylene-propylene elastomer, EPR), an outer semi-conducting screen 2.1, a semi-conducting taped layer 3, metal braiding 4 (e.g. consisting of tinned copper wires of circular cross-section), a first composite layer 9 as defined in the invention, an inner sheath comprising a polyester tape 5 and tinned copper wires 6, a polyester tape 7, a second composite layer 9 as defined in the invention, and an outer sheath 8 (e.g. of elastomer).

(10) The present invention is illustrated in the following examples. They do not limit the overall scope of the invention as presented in the claims. The ratios of the oxides are molar ratios and the percentages stated are percentages by weight.

EXAMPLES

(11) The raw materials used in the examples are listed below: aqueous solution of sodium silicate at about 50 wt % of the waterglass type, Simalco, of formula Na.sub.2O.2SiO.sub.2 and with SiO.sub.2/Na.sub.2O molar ratio of about 2, aluminosilicate Aluminosilicate, PoleStar 200R, Imrys, with Al.sub.2O.sub.3/SiO.sub.2 molar ratio of 41/55 (i.e. about 0.745), tap water, sodium hydroxide, Sigma Aldrich, of purity>85%, carboxymethylcellulose, Aqualon, Ashland, glycerol, 8400, Roquette, expanded graphite, from the company LUH, GHL PX 98 HE.

(12) Unless stated otherwise, all these raw materials were used as received from the manufacturers.

Example 1: Preparation of a Fire-Resistant Device According to the Invention

(13) A solution of alkaline silicate was prepared by mixing 252 g of aqueous solution of sodium silicate, 276 g of water and 54 g of sodium hydroxide. Then 288 g of aluminosilicate was mixed with the solution of alkaline silicate to form an aluminosilicate geopolymer composition.

(14) Said aluminosilicate geopolymer composition therefore comprised: 14.5 wt % of sodium silicate, 6.2 wt % of sodium hydroxide, 33.1 wt % of aluminosilicate, and 46.2 wt % of water.

(15) The aluminosilicate geopolymer composition comprised about 53.8 wt % of solid materials relative to the total weight of said composition.

(16) Separately, a solution of cellulose derivative was prepared by mixing 83.5 g of carboxymethylcellulose (CMC) and 438.5 g of glycerol.

(17) The solution of cellulose derivative was added to the aluminosilicate geopolymer composition in order to form a composite composition.

(18) The composite composition comprised 6.0 wt % of CMC, 31.5 wt % of glycerol, 20.7 wt % of aluminosilicate, 3.9 wt % of potassium hydroxide, 9.0 wt % of sodium silicate and 28.9 wt % of water.

(19) The composite composition was extruded in the form of a tape using a MAPRE extruder.

(20) The tape had a thickness of about 3.5 mm.

Example 2: Preparation of a Fire-Resistant Device According to the Invention

(21) A solution of alkaline silicate was prepared by mixing 95 g of aqueous solution of sodium silicate, 103 g of water and 21 g of sodium hydroxide. Then 108 g of aluminosilicate was mixed with the solution of alkaline silicate to form an aluminosilicate geopolymer composition.

(22) Said aluminosilicate geopolymer composition therefore comprised: 14.5 wt % of sodium silicate, 6.5 wt % of sodium hydroxide, 33.0 wt % of aluminosilicate, and 46.0 wt % of water.

(23) The aluminosilicate geopolymer composition comprised about 54 wt % of solid materials, relative to the total weight of said composition.

(24) Separately, a solution of cellulose derivative was prepared by mixing 282 g of carboxymethylcellulose (CMC), and 1480 g of glycerol.

(25) The solution of cellulose derivative was added to the aluminosilicate geopolymer composition in order to form a composite composition. Then 208 g of expanded graphite is added to the composite composition, and the resultant mixture is mixed for 10 min.

(26) The composite composition comprised 12.3 wt % of CMC, 64.4 wt % of glycerol, 4.7 wt % of aluminosilicate, 0.9 wt % of sodium hydroxide, 2.1 wt % of sodium silicate, 9.0 wt % of expanded graphite, and 6.6 wt % of water.

(27) The composite composition was extruded hot around an elongated electrically conducting element made of copper with a section of 50 mm.sup.2 using an extruder sold under the trade name ANDOUARD. The temperature inside the extruder ranged from about 40 C. to 95 C., from the hopper 40 C. to 95 C. at die outlet.

(28) The layer thickness was about 3.5 mm.

(29) The cable obtained comprised an elongated electrically conducting element surrounded by an electrically insulating composite layer according to the invention.

(30) The composite layer of the cable according to the invention was evaluated for fire resistance performance according to standards IEC 60331-11 and IEC 60331-21. The cable as obtained in example 2, and for comparison a cable not according to the invention, not comprising the composite layer of the invention (i.e. the elongated electrically conducting element alone), were subjected to a voltage of 10 kV at 750 C.

(31) The results of this test are presented in Table 1 below:

(32) TABLE-US-00001 TABLE 1 Time before breakdown Cable Voltage applied (in min) Cable according to the 10 kV 45 invention from example 2 Cable not according to the 10 kV 13 invention

(33) The results presented in Table 1 confirm the improved fire resistance of the cable of the invention.