Method of manufacturing a fire-resistant and/or fire-retardant cable

Abstract

A method of manufacturing a cable includes at least one elongated electrically conducting element and at least one composite layer surrounding the elongated electrically conducting element. The composite layer is obtained from at least one step of impregnation of a non-woven fibrous material with a geopolymer composition.

Claims

1. A method of manufacturing a cable having at least one elongated electrically conducting element and at least one composite layer surrounding said elongated electrically conducting element, said method comprising the steps of: i) impregnating a non-woven fibrous material with a geopolymer composition, in order to form a tape impregnated with said geopolymer composition, ii) drying the impregnated tape obtained in step i), in order to form a dried impregnated tape, and iii) applying the dried impregnated tape obtained in step ii) around the cable comprising at least one elongated electrically conducting element, in order to form said at least one composite layer surrounding said elongated electrically conducting element.

2. The method according to claim 1, wherein the non-woven fibrous material is selected from at least one of cellulosic materials, materials based on synthetic organic polymers, glass fibres, and a mixture thereof.

3. The method according to claim 1, wherein the geopolymer composition is an aluminosilicate geopolymer composition.

4. The method according to claim 1, wherein step i) is carried out by coating-impregnation.

5. The method according to claim 1, wherein step i) is carried out by passing the non-woven fibrous material through a coating device supplied with the geopolymer composition.

6. The method according to claim 1, wherein step ii) is carried out at a temperature of at most 120° C.

7. The method according to claim 1, wherein step ii) is carried out at a temperature of at least 50° C.

8. The method according to claim 1, wherein step iii) of applying of the dried impregnated tape around the cable comprising the at least one elongated electrically conducting element is carried out by wrapping the dried impregnated tape around the cable.

9. The method according to claim 8, wherein the wrapping is longitudinal.

10. The method according to claim 1, wherein step iii) is carried out by passing the dried impregnated tape through a confining device.

11. The method according to claim 1, wherein said method further comprises, after step iii), a step iv) of an application of an external protective sheath around the at least one composite layer.

12. The method according to claim 11, wherein step iv) is carried out by extrusion.

13. The method according to claim 1, wherein said method of steps i) to iii) are a continuous method.

14. The method according to claim 13, wherein the non-woven fibrous material is arranged on a distributor, and said non-woven fibrous material is distributed continuously for carrying out at least steps i) to iii).

15. The method according to claim 14, wherein step i) is carried out by passing the non-woven fibrous material through a coating device supplied with the geopolymer composition at a flow rate D (in kg/min), the distributor delivers the non-woven fibrous material at a speed V (in km/min), and the ratio D/V ranges from 20 to 50 kg of geopolymer composition per km of non-woven fibrous material.

Description

EXAMPLES

Brief Description of the Drawings

(1) The appended drawings illustrate the invention:

(2) FIG. 1 shows a schematic view of an electric cable as obtained by the method according to the invention.

(3) FIG. 2 shows a schematic view of the method according to the invention.

(4) For clarity, only the elements essential for understanding the invention are shown schematically in these figures, and they are not drawn to scale.

DETAILED DESCRIPTION

(5) The electric cable 100, illustrated in FIG. 1, corresponds to a fire-resistant electric cable of type K25 or RZ1K.

(6) This electric cable 100 comprises four elongated electrically conducting elements 10, each of which is insulated with an electrically insulating layer 20, and, successively and coaxially around these four elongated insulated electrically conducting elements (10, 20), a composite layer 30 as defined in the invention surrounding the four elongated insulated electrically conducting elements (10, 20), and an outer sheath 40 of type HFFR surrounding the composite layer 30 as defined in the invention, and is advantageously in the form of a tape.

(7) FIG. 2 is a schematic view of the method according to the invention, carried out continuously. In particular, a non-woven fibrous material 1 in the form of a tape is put on a winder 2, unwound and brought up to a coating die 3 supplied with a geopolymer composition 4, in order to allow impregnation of the non-woven fibrous material 1 with said geopolymer composition [step i)]. Then the impregnated tape is transported to an oven 5, to allow it to be dried [step ii)]. The dried impregnated tape is then brought into a confining device 6, through which a cable comprising at least one elongated electrically conducting element is travelling, in order to allow longitudinal wrapping of the dried impregnated tape around the cable, and thus form said composite layer surrounding said elongated electrically conducting element [step iii)], and finally the cable obtained passes through an extrusion head 7 for forming the external protective sheath [step iv)].

(8) The following examples provide an illustration of the present invention. They do not in any way limit the overall scope of the invention as presented in the claims.

(9) The raw materials used in the examples are listed below: aqueous solution of a first sodium silicate at about 50 wt %, of the “waterglass” type, Simalco, sodium silicate with SiO.sub.2/Na.sub.2O molar ratio of about 2.0, aqueous solution of a second sodium silicate at about 38 wt %, of the “waterglass” type, Simalco, sodium silicate with SiO.sub.2/Na.sub.2O molar ratio of about 3.4, first metakaolin, PoleStar® 450, Imérys, with Al.sub.2O.sub.3/SiO.sub.2 molar ratio of 41/55 (i.e. of about 0.745), kaolin calcined at a temperature of about 700° C., second metakaolin, PoleStar® 200R, Imérys, with Al.sub.2O.sub.3/SiO.sub.2 molar ratio of 41/55 (i.e. of about 0.745), kaolin calcined at a temperature of about 1000° C., and non-woven polyester material, GT320, GECA TAPES.

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

Example 1: Preparation of a Fire-Resistant Cable by a Method According to the Invention

(11) A geopolymer composition was prepared as follows: an aqueous solution of alkaline silicates was prepared by mixing 40 g of an aqueous solution at 50 wt % of a first sodium silicate and 40 g of an aqueous solution at 38 wt % of a second sodium silicate. Then 10 g of a first metakaolin and 10 g of a second metakaolin were mixed with the aqueous solution of alkaline silicates. Said geopolymer composition comprises about 55.2 wt % of solid materials, relative to the total weight of said geopolymer composition.

(12) A non-woven fibrous polyester material in the form of a tape is put on a winder, unwound at a speed of about 50 m/min, and brought up to a coating die supplied with said geopolymer composition at a flow rate of 1.25 kg/min, in order to allow impregnation of the non-woven fibrous material with the geopolymer composition. The geopolymer composition has a temperature of about 40° C.

(13) The impregnated tape is then brought to a first IR oven operating at a temperature of 800° C., then a second IR oven operating at a temperature of 800° C., and finally to a third IR oven operating at a temperature of 800° C., in order to allow drying of the impregnated tape.

(14) The dried impregnated tape is then brought into a confining device through which a low-voltage cable is travelling, in order to allow longitudinal wrapping of the impregnated tape around the cable. The cable comprises 5 copper conductors of section 1.5 mm.sup.2, each of the conductors being surrounded with an electrically insulating layer based on XLPE. At the end of the step of application of the impregnated tape around the cable, a composite layer surrounding the insulated conductors is obtained.

(15) The composite layer formed has a thickness of 0.5 mm.

(16) The assembly obtained is then covered by hot extrusion with a protective polymer sheath based on a mixture HFFR produced by NEXANS based on polyethylene and fireproofing fillers, said sheath having a thickness of about 2 mm. A cable according to the invention has thus been obtained. The flame-retardant performance of the cable is determined according to standard EN50399. 15 sections of cable positioned on a vertical ladder are exposed to a flame with a power of 20 kW for 20 min.

(17) The results are reported in Table 1 below:

(18) TABLE-US-00001 TABLE 1 Class according Performance parameters Values to EN50399 pHRR (kW) 13.8 B2 Time at peak HRR (s) 912 THR (MJ) 5.2 FIGRA (w/s) 23.6 Flame propagation (m) 0.56 Flaming droplets None d0 SPR (m.sup.2/s) 0.03 s1 Time at peak SPR (s) 876 TSP (m.sup.2) 28.12

(19) In this table, the acronym HRR corresponds to the expression “Heat Release Rate”, which informs on the heat flow, the acronym THR corresponds to the expression “Total Heat Release”, which informs on the amount of heat released during combustion, the acronym FIGRA corresponds to the expression “Fire GRowth rAte”, which informs on the growth rate of the fire, the acronym SPR corresponds to the expression “Smoke Production Rate”, which informs on the rate of production of smoke, and the acronym TSP corresponds to the expression “Total Smoke Production”, which informs on the total amount of smoke produced.

(20) These results demonstrate that the cable according to the invention displays the maximum fire protection properties with respect to the requirements of the European standard EN50399.