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

Abstract

The present invention relates to a method for manufacturing a cable comprising at least one elongate electrically conductive element, at least one composite layer surrounding the elongate electrically conductive element, the composite layer comprising a non-woven fibrous material impregnated by a geopolymer material, and at least one polymer sleeve surrounding the composite layer, the method using a tube of plastic material to facilitate the extrusion of the polymer sleeve around the composite layer.

Claims

1. A method for manufacturing a cable having at least one elongate electrically conductive element, at least one composite layer surrounding said elongate electrically conductive element, said composite layer comprising a nonwoven fibrous material impregnated with a geopolymer material, and at least one polymer sheath surrounding said composite layer, said method the steps of: i) passing a cable comprising at least one elongate electrically conductive element, and at least one nonwoven fibrous material impregnated with a geopolymer composition surrounding said elongate electrically conductive element, into a plastic tube, and ii) extruding a polymer sheath using an extruder comprising at least one extruder head equipped with a die and a punch, wherein a portion of said plastic tube is inserted into the extruder head and is configured to prevent contact between the geopolymer composition and the punch of the extruder head.

2. The method as claimed in claim 1, wherein the plastic tube comprises a polymer material selected from the polyaryletherketones.

3. The method as claimed in claim 1, wherein the plastic tube is configured such that the distance “d” between the outer surface of the nonwoven fibrous material and the inner surface of said tube is at most 1 mm.

4. The method as claimed in claim 1, wherein the portion of the tube that is inserted into the extruder head comprises an end which is connected to a plastic insert configured to adapt to the punch of the extruder head.

5. The method as claimed in claim 1, wherein the nonwoven fibrous material is selected from cellulosic materials, materials based on synthetic organic polymers, glass fibers and a mixture thereof.

6. The method as claimed in claim 1, wherein the geopolymer composition is an aluminosilicate geopolymer composition.

7. The method as claimed in claim 1, wherein step ii) is carried out at a temperature ranging from 140° C. to 225° C.

8. The method as claimed in claim 1, wherein said method additionally comprises, before step i), a step i0) of manufacturing the cable comprising at least said elongate electrically conductive element and at least said nonwoven fibrous material impregnated with the geopolymer composition surrounding said elongate electrically conductive element, said step i0) comprising the following substeps: a) preparing a geopolymer composition, b) applying a nonwoven fibrous material around a cable comprising at least one elongate electrically conductive element, said nonwoven fibrous material being in the form of a tape, and c) impregnating the cable/nonwoven fibrous material assembly with said geopolymer composition.

9. The method as claimed in claim 8, wherein substep b) is implemented by passing the tape into a constricting device.

10. The method as claimed in claim 8, wherein substep c) is carried out by dip coating, using an impregnation bath which comprises the geopolymer composition and into which is passed the cable comprising at least one elongate electrically conductive element and a nonwoven fibrous material surrounding said elongate electrically conductive element.

11. The method as claimed in claim 8, wherein said method is a continuous method.

12. The method as claimed in claim 11, wherein the nonwoven fibrous material is disposed on a distributor, and said material is continuously distributed for implementing at least steps i0), i) and ii).

13. The method as claimed in claim 11, wherein substep b) is implemented by passing the nonwoven fibrous material into a constricting device through which a cable comprising at least one elongate electrically conductive element runs, and then the cable thus obtained passes into an impregnation bath comprising the geopolymer composition according to substep c), and then the cable thus impregnated exits the impregnation bath and enters the plastic tube according to step i), a portion of said tube being inserted into the extruder head, and lastly the cable confined within said tube is brought into the die of the extruder head so as to enable the extrusion of the polymer sheath around the cable according to step ii).

14. The method as claimed in claim 11, wherein the running speed of the cable in substep c) and steps i) and ii) ranges from 10 m/min to 600 m/min.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0236] The appended drawings illustrate the invention:

[0237] FIG. 1 represents a schematic view of an electrical cable as obtained by the method according to the invention.

[0238] FIG. 2 represents a schematic view of the method according to the invention.

[0239] FIG. 3 represents several 3D views of the arrangement of the various parts employed in the method of the invention.

[0240] FIG. 4 shows a cross section of part of the extruder during the method of the invention.

[0241] For the sake of clarity, only the elements essential for understanding the invention have been represented schematically in these figures, and they are not shown to scale.

[0242] The electrical cable 10A, shown in FIG. 1, corresponds to a fire-resistant electrical cable of K25 or RZ1K type.

[0243] This electrical cable 10A comprises four elongate electrically conductive elements 100, each being insulated with an electrically insulating layer 200, and, successively and coaxially around these four insulated elongate electrically conductive elements (100, 200), a composite layer 300 as defined in the invention surrounding the four insulated elongate electrically conductive elements (100, 200), and an outer sheath 400 of HFFR type surrounding the composite layer 300 as defined in the invention.

[0244] FIG. 2 illustrates a schematic view of the method according to the invention implemented continuously. In particular, a nonwoven fibrous material 1 in the form of a tape is placed on a winder 2, unwound and fed to a constricting device 3 through which a cable comprising at least one elongate electrically conductive element 4 (bare cable 4) runs, in order to enable the longitudinal wrapping of the tape 1 around the cable 4. Then, the cable obtained and comprising the elongate electrically conductive element and said nonwoven fibrous material surrounding said elongate electrically conductive element 5 pass into an impregnation bath 6 comprising a geopolymer composition 7, so as to allow impregnation of the nonwoven fibrous material 1 by said geopolymer composition 7. The impregnated cable 8 obtained then passes into the plastic tube 9 (e.g. PEEK tube) by means of an extension tube 10 directly connected to the impregnation bath 6, in order to allow the confinement of said cable when it enters the extruder head 11 [step i)]. The plastic tube 9 is connected at its end to a plastic insert 12 (e.g. PEEK insert) configured to adapt to the punch 13 of the extruder head 11. The cable 8 confined in the plastic tube 9 is thus brought into the die 14 of the extruder head 11 via the punch 13, in order to enable the extrusion of the polymer sheath around the cable while preventing any contact of the geopolymer composition with the punch 13 and the metal tools of the extruder head [step ii)].

[0245] FIG. 3 shows several 3D views of the arrangement of the various parts employed in the method of the invention. In particular, FIG. 3a shows the impregnation tank 6, the extension tube 10, the plastic tube 9, and the plastic insert 12. FIG. 3b shows more specifically the punch 13 and the plastic insert 12 configured to adapt to said punch 13. FIG. 3c shows more specifically the die 14. FIG. 3d shows more particularly a distributor 15 which makes it possible to distribute the molten polymer material used to form the polymer sheath, the material being located between the punch and the die at the time of extrusion.

[0246] FIG. 4 shows a cross-sectional view of part of the extruder and shows the arrangement of the various parts during the extrusion of the sheath when the method of the invention is implemented. In particular, FIG. 4 shows an impregnated cable 8 comprising an elongate electrically conductive element 4, and the composite layer (1, 7) obtained from a nonwoven fibrous material 1 impregnated with a geopolymer composition 7 surrounding said elongate electrically conductive element 4. The composite layer (1, 7) is surrounded by the plastic tube 9, and the plastic tube 9 (e.g. PEEK tube) is connected at its end to a plastic insert 12 (e.g. PEEK insert) configured to adapt to the punch 13 of the extruder head. The impregnated cable 8 confined in the plastic tube 9 is thus brought into the die 14 of the extruder head via the punch 13, in order to enable the extrusion of the material 16 of the polymer sheath around the cable while preventing any contact of the geopolymer composition 7 with the punch 13 and the metal tools of the extruder head [step ii)].

[0247] The following examples illustrate the present invention. They do not serve to limit the overall scope of the invention as presented in the claims.

EXAMPLES

[0248] The starting materials used in the examples are listed below: [0249] approximately 50% by weight aqueous solution of a first sodium silicate of “waterglass” type, Simalco, sodium silicate of SiO.sub.2/Na.sub.2O molar ratio of about 2.0, [0250] approximately 38% by weight aqueous solution of a second sodium silicate of “waterglass” type, Simalco, sodium silicate of SiO.sub.2/Na.sub.2O molar ratio of about 3.4, [0251] first metakaolin, PoleStar® 450, Imerys, of Al.sub.2O.sub.3/SiO.sub.2 molar ratio of 41/55 (i.e. about 0.745), kaolin calcined at a temperature of about 700° C., [0252] second metakaolin, PoleStar® 200R, Imerys, of Al.sub.2O.sub.3/SiO.sub.2 molar ratio of 41/55 (i.e. about 0.745), kaolin calcined at a temperature of about 1000° C., and [0253] nonwoven polyester material, GT320, GECA TAPES.

[0254] Unless stated otherwise, all of these starting materials were used as received from the manufacturers.

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

[0255] A geopolymer composition was prepared as follows: an aqueous solution of alkali metal silicates was prepared by mixing 40 g of a 50% by weight aqueous solution of a first sodium silicate and 40 g of a 38% by weight aqueous solution 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 alkali metal silicates. Said geopolymer composition comprises about 55.2% by weight of solids, relative to the total weight of said geopolymer composition.

[0256] The geopolymer composition thus obtained is placed in an impregnation bath configured to allow the passage of the cable within said impregnation bath.

[0257] In this example, a low-voltage cable comprising five copper conductors of cross section 1.5 mm.sup.2, each of the conductors being surrounded with an electrically insulating layer based on XLPE, is manufactured beforehand.

[0258] A nonwoven fibrous polyester material in the form of a tape is placed on a winder, unwound at a speed of about 100 m/min and brought into a constricting device through which said low-voltage cable runs, in order to enable the longitudinal wrapping of the tape around the cable.

[0259] At the end of the step of applying the tape around the cable, said cable is brought to an impregnation bath comprising said geopolymer composition at a speed of about 100 m/min.

[0260] Then, the cable thus impregnated passes into a PEEK tube comprising at one end a conical-shaped PEEK insert, said tube being partially inserted into an extruder head equipped with a die and a conical-shaped punch.

[0261] When the cable reaches the PEEK insert, the cable is then covered by extrusion at a temperature of 198° C. with a polymer sheath based on an HFFR mixture produced by NEXANS and comprising polyethylene and flame-retardant fillers.

[0262] The composite layer thus formed has a thickness of 0.5 mm, and said sheath thus formed has a thickness of about 2 mm.

[0263] A cable according to the invention was thus obtained. The flame 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.

[0264] The results are reported in table 1 below:

TABLE-US-00001 TABLE 1 Class according to Performance parameters Values 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

[0265] In this table, the acronym HRR corresponds to the expression “Heat Release Rate” providing information on the heat flow; the acronym THR corresponds to the expression “Total Heat Release”, providing information on the amount of heat released during combustion; the acronym FIGRA corresponds to the expression “FIre GRowth rAte”, providing information on the rate of growth of the fire or the acceleration in the production of energy; the acronym SPR corresponds to the expression “Smoke Production Rate”, providing information on the rate of production of smoke, and the acronym TSP corresponds to the expression “Total Smoke Production”, providing information on the total amount of smoke produced.

[0266] These results demonstrate that the cable according to the invention exhibits maximum fire protection properties with respect to the requirements of European standard EN50399.