FR2515410A1 - MATERIAL FOR INSULATION AND SLEEVES OF ELECTRIC CABLES, AND ELECTRIC CABLES EQUIPPED WITH INSULATION AND SHEATHING IN THIS MATTER - Google Patents

Abstract

MATERIAL FOR INSULATION AND SHEATHING FOR ELECTRIC CABLES OF THE TYPE WITH REDUCED EMISSION OF SMOKE DURING FIRE. IT CONSISTS OF A MIXTURE OF ELASTOMERIC MATERIAL IN WHICH CHROMIC ANHYDRIDE IS PRESENT AS A CONSTITUENT. THE INVENTION ALSO CONCERNS CABLES EQUIPPED WITH AN INSULATION 2 ANDOR WITH A SHEATH 3 CONSTITUTING THE ABOVE MATERIALS.

Description

The present invention relates to a material for the manufacture of insulation

  and / or electrical cable sheaths Particularly suitable for the formation of insulation and / or electrical cable sheaths commonly referred to by branch technicians as cable emitting cables.

  reduced smoke emission during combustion.

  The present invention furthermore relates to electrical cables whose insulation and / or sheath are made of

  of the material to which the invention relates.

  Materials for the manufacture of isolates are known

  and / or sheaths of electrical cables called reduced smoke emission during combustion and it is known

  cables of the type just mentioned.

  Known materials for the manufacture of insulations and / or sheaths for electrical cables with reduced smoke emission during combustion normally consist of polymer blends containing as

  an ingredient in the mixture of aluminum hydroxide.

  The presence of aluminum hydroxide is expected to reduce the amount of smoke that is formed In fact, in the presence of a fire, the aluminum hydroxide is decomposed into alumina and water following an endothermic reaction which, by absorbing heat, opposes the fire In addition,

  the release of water in the decomposition of aluminum hydroxide

  During a fire, it is possible to reduce the amount of black smoke that forms in the combustion, and this leads to a greater transparency of the fumes that form. Obtaining transparent fumes in the event of an accidental fire in which an insulation and / or a sheath of a cable can be found is particularly important when the cable is in a confined environment so as to enable the person find in this environment to intervene easily for localization

  of the fire and the work of extinction.

  The puai insulation materials and sheaths for known electric cables and known electric cables provided with such isolations and / or sheaths do not give an answer

  satisfactory with regard to the problem of trans-

  of smoke when, for any reason, the

  cable comes to be in a fire.

  The object of the invention is to improve the materials for insulations and / or sheaths of cables and consequently the electric cables provided with insulations and sheaths with regard to the transparency of the fumes when they occur.

find in a fire.

  The invention relates to a material for insulation and electrical cable sheaths characterized in that it comprises a mixture based on a polymer chosen from ethylene-propylene rubber, ethylenepropylene-diene, polyethylene, ethylene-acetate copolymers vinyl, ethylene-ethyl acrylate, ethylene-methyl acrylate,

  polyvinyl chloride, chlorosulphonated polyethylene and poly-

  chloroprene, in which chromic anhydride is

  present as an ingredient of the mixture.

  The present invention will be better understood by means of

  the detailed description given by way of example, and by

  therefore not exhaustive, referring to the figure of the drawing

  appended which represents a cable according to the invention.

  According to the most general concept of the present invention, it relates to a material for insulation and / or electrical cable sheaths consisting of a mixture based on

  of polymers normally used in the manufacture of

  cables and / or cable sheaths which contain as their

  killing chromic anhydride mixture.

  An electric cable with an insulation and / or sheath made of a mixture having the characteristics indicated above is also included in the most important concept.

general principle of the invention.

  The figure shows an electric cable according to the invention. As shown in the figure, the electrical cable has a conductor I consisting for example of a conductive material wire or a bundle of conductive material son joined together, coated with an insulation 2, which is at its

tower covered with a sheath 3.

  Insulation 2 generally consists of a mixture of

  polymer of the type normally used for forma-

  electrical cable insulation in which there is, however, as the constituent of the mixture, chronic anhydride.

  In particular, the insulation 2 consists of a metal

  lange based on polymers selected from rubber

  ethylene-propylene, ethylene-propylene-diene, poly-

  ethylene; ethylene-vinyl acetate copolymers, ethyl

  ethylene-ethyl acrylate, ethylene-methyl acrylate, wherein is present as a constituent of the chromic anhydride mixture in an amount of from 0.1 to parts by weight per 100 parts by weight of base polymer and preferably in an amount between

  1 and 4 parts by weight per 100 parts by weight of poly-

basic mother.

  A mixture particularly suitable for the manufacture

  cable insulation is as follows:

  in which the quantities indicated are expressed in

  by weight per 100 parts by weight of base polymer ethylene-propylene rubber 100 parts by weight calcium carbonate 80 "" dicumyl peroxide 2.8 "" "zinc oxide 4" "" stearic acid 1 "" "coagents The sheath 3 of the cable is generally a mixture of a polymer of the type normally used for a sheath of an electric cable, in which chromic anhydride is nevertheless present in

as a constituent of the mixture.

  In particular, the sheath 3 consists of a metal

  lange based on polymers chosen from polyvinyl chloride, chlorosulphonated polyethylene, polychloroprene

  which contains as constituent of chromic anhydride

  in a quantity of between 0.1 and 20 parts

  weight per 100 parts by weight of polymer base and of

  in an amount between 1 and 4 parts in

  weight per 100 parts by weight of base polymer.

  A particularly suitable mixture for the formation of electrical cable ducts is that indicated below in which the amounts indicated are expressed in parts by weight per 100 parts by weight of chlorosulfonated polyethylene base polymer 100 trioctyl trimellitate dibutyl dithio talc With the mixture indicated above, that is to say with the mixture for-the formation of the insulation of a cable according to the invention and the mixture for the formation of the insulation of a cable according to the invention and the mixture for the forming the sheath of a cable according to the invention, experimental tests were carried out according to the standard 258-1976 of the National Fire

Protection Association (N F P A).

  For these tests, specimens consisting of

  killed of square platelets of mixtures having the compositions indicated above, with a thickness of 3 mm and 76.2 mm

next to.

  The test pieces were introduced into a measuring apparatus described in the above standard which comprises a hermetically closed parallelepiped chamber in which there is a support for the test tube to which six small burners correspond, the flame of which is obtained by the

  combustion of a mixture of propane and air.

  The hermetically sealed chamber further contains, in front of the test piece, a device capable of providing radiant energy consisting essentially of a small tube of ceramic material in which a resistance is housed.

  powered by electric current.

  The parallelepipedic chamber is provided on the wall

  from the bottom and on the wall opposite to it from ma-

  transparent to the light so as to allow the passage of a light beam in the chamber For this purpose,

  below the bottom wall of the chamber

  a light source of luminous intensity

  predetermined range 1 while a photometer present

  above the upper wall of the parallelepipedic chamber measures the intensity of the light striking it after passing through the chamber, expressed by the optical density

  specific content of this room.

  The tests with the apparatus summarily described above

  The above were carried out as follows:

  The test specimens were dried beforehand

  24 hours at a temperature of 60 ° C and then conditioned by placing them in an atmosphere at a temperature of 230 ° C.

  in which the relative humidity was 50%.

  After the above treatment, the test started with each of the specimens introduced into the parallelepiped chamber with the burners on and with the

  device that provides radiant energy in operation

  the photometer placed on this parallelepiped chamber the specific optical density of the smoke four minutes after the start of

  the test and the maximum specific optical density of the fumes.

  With the same apparatus, identical tests were made on known cable insulators and known cable duct materials to record the specific optical density of the fumes four minutes after the start of the test and the optical density

maximum specific fumes.

  As known cable insulators, two mixtures having the above-mentioned base compositions and respectively constituting examples of an insulation and a sheath according to the invention in which

  chromic anhydride was absent.

  In particular, tests were carried out on samples consisting of the following mixtures: A) Known mixture of cable insulators which differs from that indicated as a particular case of an insulation for cables according to the invention by the absence of chromic anhydride . B) Known mixture for cable sheaths which differs from that indicated as a special case of a cable sheath according to the invention in that the chromic anhydride is absent. In the following, both for the blends according to the invention and for mixtures of known type, the oxygen index defined below was determined on the basis of ASTM D 2863. The average results of the tests appear in the

table below.

D 4 Dm 1 0.

  mixture of the invention for insulation of electric cables 6 60 26 mixture of the invention for electric cable sheath 23.5 357 25 mixture known for insulation of electric cables 150 300 28 mixture known for electric cable sheath 400> 500 27 - o : D 4 is the specific optical density of the fumes 4 minutes

after the start of the test.

  Dm is the maximum optical density of the fumes.

  I.0, commonly referred to as the oxy-

  gene, represents the quantity m nlh oxygen in a mixture of oxygen and nitrogen necessary to allow still the combustion of a specimen as defined

by ASTM D 2863.

  Examination of the results provided by the experimental tests

  mentalities in the table above shows that the

  present invention has achieved the goals.

  Indeed, the experimental results clearly indicate that the maximum specific optical density of the fumes obtainable with an insulating material for cables and for cable sheaths according to the invention during a combustion is significantly lower than that of the known insulating materials. and known sheath materials for so-called reduced emission cables

during a fire.

  This obviously also means that a cable isolated and / or provided with a sheath according to the invention satisfactorily solves the problem of avoiding the formation of opaque fumes when the cable is in an environment where a fire occurs. The results obtained with the solution according to the present invention are really surprising in that it is not possible to give a certain explanation of the reasons why in the presence of chromic anhydride,

  it is possible to reduce in the exceptional way de-

  shown by experimental tests the black formation of

  smoke which is the cause of opaque fumes.

  It is likely that the presence of chromic anhydride

  the insulation and / or sheath of a cable acts directly or indirectly as a catalyst against

  pyrolysis of this sheath and / or insulation, the decomposition of which

  position gives birth to the lampblack.

Claims (9)

  1. Material for insulation and electrical cable ducts, characterized in that it comprises a mixture   based on a polymer selected from ethylene-rubber   propylene, ethylene-propylene-diene, polyethylene, ethylene-vinyl acetate, ethylene-ethyl acrylate, ethylene-methyl acrylate, polyvinyl chloride, polyethylene-chlorosulfone and polychloroprene, in which anhydride chromic is present as an ingredient of the mixture.   2 Insulation material and cable sheaths   according to claim 1, characterized in that the chromic anhydride is present in the mixture in an amount of between 0.1 and 20 parts by weight to   parts by weight of the polymer serving as a base for the mixture.   3 Material for insulation and cable sheaths   according to claims 1 and 2, characterized in that   that the chromic anhydride is present in the mixture in an amount of preferably between 1 and 4 parts in   weight per 100 parts by weight of the base polymer of the lange.   4. Insulating material for electric cables according to   any one of the preceding claims, characterized   in that the mixture of which it is composed has the following composition: ethylene-propylene rubber 100 parts by weight calcium carbonate 80 "" dicumyl peroxide 2.8 "" zinc oxide 4 "" "stearic acid 1" "" coagents crosslinking 2 "antioxidant" "aluminum hydroxide 70" "" chromic anhydride 3 "" " 5. Material for electrical cable ducts according to   any one of the preceding claims, characterized   in that the mixture of which it is composed has the following composition: polyethylene-chlorosulfate 100 parts by weight trioctyl trimellitate 15 "" talc 30 "" "dibutyl-dithio-carbamate nickel 2" "" accelerator 3 "" " chromic anhydride 3 "" " Electrical cable comprising a conductor and an insulator, characterized in that this insulator consists of a mixture based on a polymer chosen from rubber   ethylene-propylene, ethylene-propylene-diene, polyethylene   ethylene-vinyl acetate copolymers, ethylene-   ethyl acrylate and ethylene methyl acrylate, wherein chromic anhydride is present as an ingredient of the mixture.   7. Electrical cable according to claim 6, characterized in that it comprises a sheath consisting of a mixture based on a polymer selected from polychloride   vinyl chloride, polyethylene-chlorosulphonate and polychlorinated   prene, in which chromic anhydride is present as an ingredient of the mixture, 8. Electrical cable according to any one of   Claims 6 and 7, characterized in that the anhydride   chromic content in the mixture constituting the insulation and / or the sheath of the cable is present in an amount of between 0.1 and 20 parts by weight per 100 parts by weight of base polymer of the mixture.   9. Electrical cable according to any one of   claims 6 and 7, characterized in that the quantity   of chromic anhydride present in the mixture constituting the insulation and / or the sheath of the cable is preferably between 1 and 4 parts by weight per 100 parts by weight of base polymer of the mixture.