WO2007096348A1

WO2007096348A1 - Cables having a low smoke release

Info

Publication number: WO2007096348A1
Application number: PCT/EP2007/051592
Authority: WO
Inventors: Julio A. Abusleme; Vincenzo Arcella; Anthony V Zangara
Original assignee: Solvay Solexis S.P.A.
Priority date: 2006-02-23
Filing date: 2007-02-20
Publication date: 2007-08-30
Also published as: ITMI20060328A1

Abstract

Cables comprising: primary cables coated by a perfluoropolymer; and a jacket formed of a polymeric composition comprising: (A) an ethylene, tetrafluoroethylene (TFE) and/or chlorotrifluoroethylene (CTFE) copolymer, and one or more hydrogenated monomers; (B) one or more inorganic fire-retardants, optionally treated with dispersing agents.

Description

CABLES HAVING A LOW SMOKE RELEASE

The present invention relates to cables comprising a jacket in fluoropolymers and a core formed of primary cables constituted by conducting wire pairs (metallic or optical fibres) coated by a perfluoropolymer.

More specifically the present invention relates to low smoke cables when subjected to a heat source capable to meet the most severe tests required for the cables installed in the plenum, in particular NFPA 262 (UL910 Steiner Tunnel test), preferably also the most restrictive test NFPA 255 (UL 723 test).

In more detail the present invention relates to cables wherein the jacket is formed of ethylene (E)/chlorotrifluoroethylene (CTFE) and/or tetrafluoroethylene (TFE)/one or more hydrogenated monomers fluoropolymers, and the insulating agent of the primary cables is formed of perfluoropolymers, for example hexa- fluoropropene/tetrafluoroethylene copolymers (HFP/TFE), optionally containing perfluoroalkyl vinylethers, kwown as FEP, or TFE-perfluoroalkyl vinylethers, known as PFA and MFA.

The US National Fire Protection Association (NFPA) Body has defined in the course of the years some rules and the respective tests in order to make safer and safer the building construction materials, in particular those for cables, as regards the smoke emission when subjected to a heat source.

In particular the NFPA 262 test (UL910 Steiner Tunnel test) allows to simulate the behaviour of electric wires or optical fibers installed in the air ducts evaluating the smoke density thereof; the NFPA 255 test allows to simulate the behaviour of building materials in the form used inside the buildings, for example final cables (UL 723 test), determining the smoke density and the flame propagation.

In the case of cables, the passing of the NFPA 262 test (UL910 Steiner Tunnel test), NFPA 255 (UL 723 test), allows to obtain a cable usable in environments where very severe anti-fire rules are requested. Indeed the NFPA 255 test (UL 723 test) is the most strict test as it requires a lower smoke generation in comparison with the NFPA 262 test.

Generally the passing of the NFPA 255 test for the cable buildings exemplified in the present invention (see the Examples) also implies the passing of the NFPA 259 test related to the potential heat which can be produced by building materials.

The passing of the three above tests, NFPA 262, 255 and 259, allows to define a cable as "Limited Combustible Cable" and thus to use it in environments where very strict anti-fire rules are required.

As known, the cables passing the NFPA 262 test do not necessarily pass the NFPA 255 test.

As a matter of fact the cables passing the NFPA 255 test must produce much lower smoke than those passing the NFPA 262 test. For example cables having a polyvinylidene chloride (PVC) jacket pass the NFPA 262 test but not the NFPA 255 test. See for example patent application US 2005/187,328.

Besides the passing the above tests, it is desirable the cable behaviour during the fire must maintain their physical integrity as long as possible to delay the electricity interruption. For this reason it is desirable to reduce to the minimum the dripping phenomenon of the jacket polymer and to promote the formation of a compact, not friable or poor friable "char".

Cables with the jacket and the primaries are formed of perfluoropolymers, for example FEP, having a smoke generation very reduced, are known. Generally the jacket is extruded on the primary cables already formed and twisted at high temperatures, higher than 300°C. The jacket polymer has a viscosity much higher (lower melt flow index) compared with the resin used for the primary cable to allow the passing of the NFPA 262 test (UL910 Steiner Tunnel test) and the stricter NFPA 255 test (UL 723 test). As a matter of fact it is known that a low melt flow index of the jacket polymer, comprised between 2 and 7 g/10 min (measured according to ASTM D 1238 at a 5 kg load) allows to pass the NFPA 255 test. However the polymers having said melt flow indexes are only extrudable at low rates, lower than 120 ft/min (about 37 m/min). See for example patent application US 2005/187,328.

As a matter of fact, to overcome this problem, patent application US 2005/187,328 uses a jacket composition comprising a perfluoropolymer having a high melt flow index, higher than 10 g/10 min (at a 5 kg load), a char-forming inorganic agent and a hydrocarbon polymer. This composition passes the NFPA 255 test. However it is preferable that the jacket polymer shows a melt temperature (at the extruder die outlet) during the processing lower than the second melting polymer temperature used for the primary cable insulation, for example FEP, in order to avoid possible softenings of the primary cables already twisted during the jacket extrusion. This phenomenon indeed can damage the cable electric performances due to the variation of the insulator form around the wire and/or of the insulator thickness.

It is known that non perfluorinated polymers have second melting temperatures lower than those of perfluorinated polymers. However, in applications for primary cable jacketing it is desirable that the polymers do not negatively influence the electrical properties, for example the attenuation of the electrical signal, and possess a low dielectric constant, preferably lower than 3.

Furthermore it is desirable that the cable jacket be printable with laser by conventional non contact ink-marking system. As known, the perfluoropolymers as FEP are not easily markable.

The need was therefore felt to have available cables having the following combination of properties: passing the most severe tests on the smoke release as NFPA 262 and/or

NFPA 255 (UL 723 test), in particular the latter; a jacket formed of polymers having a maximum processing temperature lower of at least 10°C than the second melting temperature of the primary polymer; a jacket with a low dielectric constant, preferably lower than 3; an easily markable jacket; generation of a compact char having a sufficient mechanical resistance so as not to leave the wires uncoated during the fire.

The Applicant has surprisingly and unexpectedly found cables overcoming the above described technical problem.

It is an object of the present invention cables comprising: primary cables formed of conducting wires coated by a perfluoropolymer, and a jacket formed of a polymeric composition comprising, (A) a copolymer of ethylene with tetrafluoroethylene (TFE) and/or chlorotrifluo- roethylene (CTFE) and one or more hydrogenated monomers, (B) one or more inorganic fire-retardants, optionally treated with dispersing agents, optionally

(C) additives selected from fillers, pigments, intumescent agents, thermal stabilizers.

Component (A) can be used under the form of blends (A') with CTFE-based (co)polymers containing at least 99% by moles of CTFE (PCTFE), the complement to 100 being formed of one or more fluorinated or hydrogenated monomers.

Copolymers (A) are preferably formed of the following monomers:

(a) ethylene from 10 to 70%, preferably from 35 to 55% by moles;

(b) a fluorinated monomer selected from tetrafluoroethylene, chlorotrifluo- roethylene, or mixtures thereof, in a percentage by moles from 30 to 90%, preferably from 45 to 65%;

(c) from 0.1 to 30%, preferably from 1 to 15% by moles with respect to the total amount of monomers (a) and (b), of a hydrogenated monomer of formula:

CH₂=CH-(CH₂)_n-R₁ (I) wherein Ri = -OR₂, -(O)_tCO(O)_pR2, wherein t and p are integers equal to 0 or 1 , n is an integer between 0 and 10; R₂ is a hydrogenated radical from 1 to 20 carbon atoms, linear and/or branched CrC₂O alkyl or cycloalkyl radical, or R₂ is H. R₂ radical may optionally contain: heteroatoms, preferably Cl, O, N; one or more functional groups preferably selected from OH, COOH, epoxide, ester, ether and double bonds.

Preferably R₂ is an alkyl radical from 1 to 10 carbon atoms containing one or more hydroxy functional groups and n is an integer from 0 to 5. Comonomers (c) are for example selected from the following classes:

1 ) acrylic monomers of formula:

CH₂=CH-CO-O-R₂ wherein R₂ has the aforesaid meaning; ethylacrylate, n-butylacrylate, acrylic acid, hydroxyethylacrylate, hydroxy- propylacrylate, (hydroxy)ethylhexylacrylate, acryl(N-alkyl)amide wherein alkyl is CrC₅, etc., can for example be mentioned;

2) vinylether monomers of formula: CH₂=CH-O-R₂ wherein R₂ has the aforesaid meaning; propylvinylether, cyclohexylvinylether, vinyl-4-hydroxybutylether, etc., can for example be mentioned;

3) vinyl monomers of the carboxylic acid of formula:

CH₂=CH-O-CO-R₂ wherein R₂ has the aforesaid meaning; vinyl-acetate, vinylpropionate, vinyl-2-ethylhexanoate, etc., can for example be mentioned;

4) unsaturated carboxylic acids of formula:

CH₂=CH-(CH₂)_n-COOH wherein n has the aforesaid meaning; the vinylacetic acid, etc. can for example be mentioned.

The preferred class of monomers (c) are acrylic monomers (1), the most preferred is n-butyl acrylate.

The preferred fluorinated comonomer (b) is chlorotrifluoroethylene (CTFE).

The copolymer E/CTFE (or E/TFE) containing hydrogenated monomeric units is known and can be prepared according to USP 6,107,393, EP 1 ,125,982.

The PCTFE percentage in blends (A') is between 1 and 75% by weight, preferably between 5 and 30% by weight.

PCTFE is a semicrystalline (co)polymer of chlorotrifluoroethylene (PCTFE) containing at least 99% by mols of chlorotrifluoroethylene, the complement to 100 being one or more hydrogenated, preferably acrylic, monomers or fluorinated monomers, preferably selected from (per)fluoroalkylvinylethers, (per)fluorodioxoles. Preferably PCTFE is a CTFE homopolymer.

Semicrystalline copolymers mean a polymer having at least a second melting enthalpy of at least 1 J/g.

The blends (A') can be prepared for example according to European patent application EP 1 ,130,056 in the name of the Applicant herein incorporated by reference. For example the (co)polymer ECTFE can be prepared by radical polymerization in the presence of the PCTFE (co)polymer. In alternative (A) (co)polymer can be prepared by radical polymerization in the presence of the ECTFE (co)polymer. These syntheses are carried out in the presence of radical initiators, preferably in suspension in an organic medium, at a temperature between -10°C and 50°C and at a pressure in the range 0.5-100 bar, preferably 5-40 bar.

The "fire retardants" (B) of the jacket composition of the invention are inorganic compounds and their percentage by weight is between 0.1 and 15%, preferably between 0.5 and 9% on the total of the composition. Examples of fire retardants are inorganic phosphates (for example ammonium phosphate), metal oxides (for example aluminum oxide, trihydrated aluminum oxide, antimony oxides, molybdenum oxide, zinc oxide), tin oxalates, boron compounds (for example borax, zinc borate, Fire- brake^®ZB), metal hydroxides, for example magnesium hydroxide, ZnSn(OH)₆, etc.

The dispersing agents to treat component (B) are those having general formula:

R- A -X

wherein A is an atom selected from Si, Ti or Zr, X is a hydrolyzable group, the two free valences being saturated with R or X, R is an oligomer of hydrogenated monomers, or R is equal to R₃, R₃ being a C_rCi₅ alkyl radical and/or C₆-Ci₅ aryl radical. The radical R₃ can optionally contain: unsaturations; one or more heteroatoms selected from O, N, S, Cl; functional groups as amines, epoxide, -SH, -OH, -CONH₂, carboxyl or sali- fied carboxyl.

The more preferred dispersing agents, in monomeric or oligomeric form, have the following structure:

(R₃)₄._mA(X)_m wherein m = 1-3, preferably m = 2 or 3; X is a hydrolyzable group, preferably X is an alkoxy group OR₄ wherein R₄ is a linear or branched C_rC₅ alkyl radical; R₃ and A are as above. Preferably A is an atom selected between Si or Ti. When A is Si preferably m = 3 and R₃ is methyl or ethyl.

The preferred dispersing agents are selected from one or more of the following: vinyltriethoxysilane, 3-aminopropyltriethoxysilane, 3-chloroisobutyl- triethoxysilane, 3-mercaptopropyltriethoxysilane, octyltriethoxysilane, diisopropoxyti- tanium bisacetylacetonate.

The addition of the dispersing agents to the inorganic fire retardants is carried out at room temperature. Then the mixture is heated to about 100°C for one or more hours. The water necessary to hydrolyze the X groups in the above formula of dispersing agents is provided by the reaction environment or by the residual humidity of the organic solutions containing the dispersing agents.

As component (B) the zinc oxide and zinc borate are preferred optionally treated with dispersing agent and mixtures thereof.

Component (C) are for example fillers, for instance polytetrafluoroethylene (PTFE), silicates, preferably PTFE; pigments, for example iron, chromium oxides, thermal stabilizers such as hindered phenols (Irganox^® 1010, Mark-260^®), organic acid scavengers such as oligomers of acrylic acid/ethylene partially salified with alkaline metal ions (Aclyn-316^®), can be mentioned. The amount of (C) is between 0 and 10% by weight based on the total of the composition.

The sum of the percentages of the components (A), (B), (C) is 100% by weight. The preferred polymeric compositions of the invention comprise the preferred components of (A), (B), (C).

The perfluoropolymer of the primary cables is a thermoprocessable semicrystalline copolymer having a second melting temperature higher than 200°C, preferably higher than 230°C, more preferably higher than 260°C.

Preferably the perfluoroplymers are selected from the following classes: (i) thermoprocessable semicrystalline copolymers of TFE with HFP, wherein preferably HFP is between 2.8 and 20% by weight (see for example USP 2,946,763); these copolymers also called FEP optionally contain monomeric units deriving from one or more perfluoroalkyl vinylethers (PAVE) CF₂=CF-O-Rf wherein R_f is a d-C₆ perfluoroalkyl group, preferably perfluoromethyl- vinylether (PMVE), perfluoroethylvinylether (PEVE) and perfluoro- propylvinylether (PPVE); more preferably HFP is between 9 and 17% by weight and PAVE 0.2-5.5% by weight; among PAVEs, perfluoroethylvinylether (PEVE) is preferred. These polymers can be prepared for example according to USP 5,677,404; in US Statutory Invention Registration Number H 130, published on 2 September 1986;

(ii) thermoplastic semicrystalline copolymers of TFE with perfluoroalkylvinylethers (PAVE) CF₂=CF-O-Rf wherein R_f is a C_rC₆ perfluoroalkyl group, preferably perfluoromethylvinylether, perfluoroethylvinylether and perfluoropropyl- vinylether wherein the total PAVE amount ranges from 1 to 20% by weight, preferably from 2 to 15% (see for example USP 3,132,123); said copolymers are preferably selected from TFE copolymers containing from 0.5 to 13% of PMVE and from 0.5 to 3% by weight of PPVE or PEVE (see for example USP 5,463,006); said copolymers optionally contain monomeric units deriving from HFP in amounts between 2.8 and 20% by weight when PAVE is higher than 5.5% by weight; or they optionally contain HFP in amounts between 0.1 and 2.8% by weight when PAVE is lower than 5.5% by weight;

(iii) thermoprocessable copolymers of tetrafluoroethylene (TFE) comprising:

(a1) from 0.1 to 15% by moles, preferably from 0.5 to 9%, of a fluorodioxole of formula:

CZ=C-Ta

O O (I)

\ /

wherein Ta is R_f or OR_f wherein R_f is a perfluoroalkyl having from 1 to 5 carbon atoms; Xi and X₂, equal to or different from each other, are -F or -CF₃; Z is selected from -F, -H, -Cl; and

(b1) from 0 to 15%, preferably from 0 to 10%, by moles of a perfluorinated monomer selected from hexafluoropropene (HFP) and perfluoroalkylvinylethers of formula CF₂=CF-ORV, wherein R'_f is a C₂-C₄ perfluoroalkyl, or mixtures thereof;

(c1) TFE being the remaining part to 100% by moles; wherein the amount of monomers (a1) ⁺(b1) is lower than or equal to 20% by moles, preferably lower than or equal to 12% by moles.

These polymers can be prepared according to EP 720,992. Preferably the primary cable perfluoropolymer is a TFE/PAVE copolymer wherein the total PAVE amount is between 1.5 and 5.5% by weight, preferably 2.5-5% by weight, optionally containing HFP in amounts from 0.1 to 9% by weight, preferably from 0.5 to 6% by weight, more preferably from 1 % to 4% by weight.

The polymeric composition usable for the jacket passing the NFPA 255 test has preferably a melt flow index value higher than 7 g/10 min, measured at 275°C (with a 5 kg load according to the ASTM D 1238 standard; 275°C being the reference temperature for E/CTFE-based fluoropolymers).

This results advantageous as it allows to extrude the jacket polymeric composition at high extrusion rates, higher than 120 ft/min (about 37 m/min) obtaining cables passing the NFPA 255 test.

This was surprising and unexpected as in the prior art cables, known having a jacket formed of perfluoropolymers with melt flow index higher than 7 g/min, measured at 372°C (with a 5 kg load, 372°C being the reference temperature for TFE-based perfluoropolymers), extrudable at rates higher than 120 ft/min, did not pass the NFPA 255 test. See patent application US 2005/187,328.

Therefore the jacket polymeric composition of the present invention results more advantageous than the FEP used in the prior art, as it can be extruded with higher extrusion rates but passing the NFPA 255 test.

The cables of the present invention can be in various forms and meet the various categories for electrical wires. For example:

I) primary: four pairs; jacket (class 5)

II) primary: 25 pairs; jacket (class 5)

III) primary: 4 pairs; crossweb; jacket (class 6)

Tests carried out by the Applicant (see the Examples) surprisingly and unexpectedly show that a cable consisting of a jacket formed of a polymer containing high percentages of hydrogen atoms and having primary cables formed of perfluorinated polymers, in particular TFE/perfluoroalkylvinylether polymers, develops a reduced amount of smokes and lower than the cable (jacket and primary cables) exclusively formed of perfluorinated polymers, in particular TFE/perfluoroalkyl- vinylethers, thus not containing hydrogen atoms.

Furthermore it has been found that in these embodiments the cable of the present invention does not generate flames, since its Flame Spread Index (FSI) is 0.

Besides it was surprising and unexpected that the cable of the present invention when subjected to a heat source does not show any dripping but only a not friable compact char.

In addition the jackets of the present invention are easily markable with systems without using inks.

Some Examples follow with illustrative but not limitative purposes of the present invention.

EXAMPLES

CHARACTERIZATION

Test NFPA 262 (UL 910 Steiner Tunnel test)

In this test the cable is subjected to combustion for 20 minutes in a chamber called "Steiner Tunnel" by following the procedure described in the above standard evaluating then the developed smoke. The smoke release is expressed as "Average smoke" and "Peak smoke". The test is considered passed when:

Average smoke is equal to or lower than 0.15;

Peak smoke is equal to or lower than 0.5.

NFPA 255 test (UL 723)

By using the combustion chamber "Steiner Tunnel" and operating under the conditions indicated by the standard, a much higher amount of cables (length) with respect to the NFPA 262 is subjected to combustion for 10 minutes. Then the "Flame Spread Index" (FSI) and the "Smoke Developed Index" (SDI) are evaluated. The test is considered passed when:

FSI is equal to or lower than 25;

SDI is equal to or lower than 50.

Melt Flow Index

It is measured according to the ASTM D 1238 standard at a predetermined temperature of the melt polymer by using a 5 kg load. The predetermined temperature for the perfluoropolymers is 372°C at 5 kg; for the composition of the present invention it is 275°C with 5 kg. EXAMPLE 1 EXAMPLE 1.1 Preparation of the copolymer E/CTFE/n-BuA 40/55/5 % by moles

In an enamelled autoclave equipped with breakwater and stirrer working at 450 rpm 5.3 I of demineralized water, 1.7 I of methyl alcohol, 20 ml of methylcyclopentane, 10 g of n-butylacrylate (n-BuA) and 2 Kg of chlorotrifluoroethylene (CTFE) have been introduced. Then the autoclave was brought to the reaction temperature of 15°C and ethylene (E) was fed up to a pressure of 8.2 absolute bar. In the auoclave the radical initiator was then continuously fed for the whole polymerization, under the form of a solution, maintained at -17°C, of trichloroacetylperoxide (TCAP) in isooctane having titre of 0.1 g TCAP/ml. Furthermore 10 g of n-butylacrylate in consumption of 20, 40, 60, 80, 100, 120, 140, 160 and 180 g of ethylene were then introduced for a total of 100 g of n-butylacrylate introduced comprising the amount initially fed.

The pressure was maintained constant for the whole polymerization by continuously feeding ethylene in the reactor up to a consumption of 200 g; in all 399 ml of initiator solution were introduced. The total duration of the polymerization was 555 minutes.

The product discharged from the autoclave was dried at 120°C for about 16 hours. The amount of dry product obtained was 1 ,200 g. EXAMPLE 1.2 Preparation of the composition of the invention

A composition was prepared containing the following components, in amounts expressed in percent by weight:

(A) 96.65% of the polymer of the Example 1.1 ;

(B) 1% of zinc borate treated with an amount equal to 2% by weight of a solution at 75% by weight of diisopropoxy-titanium bis-acetylacetonate in isopropanol; then the mixture was dried at 100°C for two hours;

0.75% of zinc oxide (purity 99.9%) in powder with particle diameter lower than 1 micron; (C) 1 % by weight of PTFE (Polymist^® F5A-EX);

0.45% by weight of MARK-260^® (thermal stabilizer);

0.15% by weight of Aclyn-316^®.

The components were mixed in a Henschel mixer for three minutes and then the composition, having a Melt Flow Index of 14 g/10 min, was extruded in pellets in a twin-screw Brabender extruder with the barrel temperature at 230°C and extrusion rate equal to 20 rpm. EXAMPLE 1.3

Preparation of the cable and smoke check according to the UL 910 Steiner Tunnel test

The pellets obtained in the Example 1.2 were jacket-cable extruded on 25 pairs twisted copper wires coated with a TFE/PMVE/PPVE copolymer 95.0/4.6/0.4 (molar composition) having a melt index of 21 g/10 min (coating thickness equal to about 7 mil corresponding to about 85 micron).

The temperature profile during the jacket extrusion was the following: barrel: 180°C-190°C; flange: 200°C; die: 220°C-235°C.

The obtained cable, having a jacket with thickness of about 16 mil (corresponding to 400 micron), was subjected to the UL 910 Steiner Tunnel test (NFPA 262) and the obtained results were the following:

Average smoke: 0.14;

Peak smoke: 0.45.

Said values allow to pass the UL 910 test. EXAMPLE 2 (comparative)

The Example 1.3 was repeated except that also for the jacket the perfluoropolymer TFE/PMVE/PPVE 95.0/4.6/0.4 (molar composition) having a melt index of 21 g/10 min was used.

The temperature profile during the jacket extrusion was the following: barrel: 315°C-400°C; flange: 400°C; die: 400°C.

The obtained cable, having a jacket thickness of about 16 mil (corresponding to 400 micron), was subjected to the UL 910 Steiner Tunnel test (NFPA 262) and the obtained results are the following:

Average smoke: 0.27;

Peak smoke: 1.59. Said values do not allow to pass the UL 910 test.

From the comparison of the data of the Examples 1 and 2 (comparative) it is surprising and unexpected that a cable constituted by a jacket formed of a copolymer E/CTFE/butyl acrylate (containing high percentages of hydrogen) and of primary cables formed of TFE-perfluoroalkylvinylethers copolymers develops a smoke amount lower than the cable (jacket and primary cables) exclusively formed of a perfluorinated copolymer as TFE/PMVE/PPVE. EXAMPLE 3

On four pairs twisted copper wires already coated (coating thickness equal to about 7 mil, corresponding to 85 micron) with a FEP perfluoropolymer, marketed as Daikin NP 101 , characterized by a MFI of 21-27 g/10 min and a melting point between 250°C-260°C (ASTM D 2116), some pellets of the composition of the Example 1.3 have been extruded thus forming a jacket.

For said extrusion an extruder having a screw diameter of 38.1 mm (1.5 inch) was used wherein the temperature profile is the following: barrel: 180°C-190°C; flange: 200°C; die: 220°C-235°C.

The extrusion has occurred at line rate higher than 200 ft/min (about 61 m/min) producing jackets surface defect free. The obtained cable, having a jacket thickness of about 12 mil (corresponding to 300 micron), was subjected to the UL 723 (NFPA 255) test and the obtained results were the following:

Flame Spread Index (FSI): 1.09;

Smoke Developed Index (SDI): 20. Said values allow to pass the UL 723 test.

During the test it was also observed that the jacket has formed a compact and not friable char and a very low dripping and the whole has burnt with little visible smoke. EXAMPLE 4

On four pairs coated twisted copper wires (coating thickness equal to about 7 mil, corresponding to about 85 micron) with a perfluoropolymer of class (ii) formed of TFE/PEVE/PMVE 97.3/1/1.7% by moles (corresponding to 95.1/2.2/2.7% by weight), said perfluoropolymer having a MFI of 27 g/10 min and a second melting temperature of 298°C, some pellets of the composition of the Example 1.3 have been extruded thus forming a jacket.

An extruder having a screw diameter of 38.1 mm (1.5 inch) was used wherein the temperature profile is the following: barrel: 180°C-190°C; flange: 200°C; die: 220°C-235°C.

The extrusion has occurred at line rate higher than 200 ft/min (about 61 m/min) producing jackets surface defect free.

The obtained cable, having a jacket thickness of about 12 mil (corresponding to 300 micron) was subjected to the UL 723 (NFPA 255) test and the obtained results were the following:

Flame Spread Index (FSI): 0;

Smoke Developed Index (SDI): 30.

Claims

1. Cables comprising: primary cables formed of conducting wires coated by a perfluoropolymer, and a jacket formed of a polymeric composition comprising,

(A) a copolymer of ethylene with tetrafluoroethylene (TFE) and/or chlorotri- fluoroethylene (CTFE), and one or more hydrogenated monomers,

(B) one or more inorganic fire-retardants, optionally treated with dispersing agents, optionally

2. Cables according to claim 1 , wherein component (A) can be used under the form of blends (A') with CTFE-based (co)polymers containing at least 99% by moles of CTFE (PCTFE), the complement to 100 being one or more fluorinated or hydrogenated monomers.

3. Cables according to claims 1-2, wherein the copolymers (A) of the jacket are preferably formed of the following monomers:

(a) ethylene from 10 to 70%, preferably from 35 to 55% by moles;

(b) a fluorinated monomer selected from tetrafluoroethylene, chloro- trifluoroethylene, or mixtures thereof, in a percentage by moles from 30 to 90%, preferably from 45 to 65%;

CH₂=CH-(CH₂)_n-R₁ (I) wherein R₁ = -OR₂, -(O)_tCO(O)_pR₂, wherein t and p are integers equal to 0 or 1 , n is an integer between 0 and 10, R₂ is a hydrogenated radical from 1 to 20 carbon atoms, linear and/or branched CrC₂O alkyl or cycloalkyl radical, or R₂ is H; R₂ radical may optionally contain: hete- roatoms, preferably Cl, O, N; one or more functional groups preferably selected from OH, COOH, epoxide, ester, ether and double bonds; preferably R₂ is an alkyl radical from 1 to 10 carbon atoms containing one or more hydroxyde functional groups and n is an integer from O to 5.

4. Cables according to claim 3, wherein comonomers (c) are selected from the following classes:

1 ) acrylic monomers of formula:

CH₂=CH-CO-O-R₂ wherein R₂ has the aforesaid meaning; preferably monomers 1 ) are selected from ethylacrylate, n-butylacrylate, acrylic acid, hydroxyethylacrylate, hydroxypropylacrylate, (hydroxy)- ethylhexylacrylate, acryl(N-alkyl)amide wherein alkyl is C1-C5;

2) vinylether monomers of formula:

CH₂=CH-O-R₂ wherein R₂ has the aforesaid meaning; preferably monomers 2) are selected from propylvinylether, cyclohexyl- vinylether, vinyl-4-hydroxybutylether;

3) vinyl monomers of the carboxylic acid of formula:

CH₂=CH-O-CO-R₂ wherein R₂ has the aforesaid meaning; preferably monomers 3) are selected from vinylacetate, vinylpropionate, vinyl-2-ethylhexanoate, etc.;

4) unsaturated carboxylic acids of formula:

CH₂=CH-(CH₂)_n-COOH wherein n has the aforesaid meaning; preferably vinylacetic acid.

5. Cables according to claims 3-4, wherein the class of monomers (c) is that of acrylic monomers (1), preferably n-butyl acrylate.

6. Cables according to claims 2-5, wherein the fluorinated comonomer (b) is chlorotrifluoroethylene.

7. Cables according to claims 2-6, wherein the PCTFE percentage in blends (A') is between 1 and 75% by weight, preferably between 5 and 30% by weight.

8. Cables according to claims 2-7, wherein the PCTFE is a semicrystalline (co)polymer containing at least 99% by moles of chlorotrifluoroethylene, the complement to 100 being one or more hydrogenated, preferably acrylic, monomers or fluorinated monomers, preferably selected from (per)fluoroalkylvinylethers, (per)fluorodioxoles; more preferably PCTFE is a CTFE homopolymer.

9. Cables according to claims 1-8, wherein the "fire retardants" (B) of the jacket composition are inorganic compounds and their percentage by weight is between 0.1 and 15%, preferably between 0.5 and 9% on the total of the composition.

10. Cables according to claim 9, wherein the fire retardants are selected from inorganic phosphates, preferably ammonium phosphate, metal oxides, preferably aluminum oxide, trihydrated aluminum oxide, antimony oxides, molybdenum oxide, zinc oxide, tin oxalates, boron compounds, preferably borax, zinc borate, Firebrake^®ZB), metal hydroxides, preferably magnesium hydroxide, ZnSn(OH)₆.

11. Cables according to claims 9-10, wherein the dispersing agents to treat component (B) are those having general formula:

R- A -X

wherein A is an atom selected from Si, Ti or Zr, X is a hydrolyzable group, the two free valences being saturated with R or X, R is an oligomer of hydrogenated monomers, or R is equal to R₃, R₃ being a C_rCi₅ alkyl radical and/or C₆-Ci₅ aryl radical; the radical R₃ can optionally contain: unsaturations; one or more heteroatoms selected from O, N, S, Cl; functional groups as amines, epoxide, -SH, -OH, -CONH₂, carboxyl or salified carboxyl.

12. Cables according to claim 11 , wherein the dispersing agents, in monomeric or oligomeric form, have the following structure:

(R₃)₄._mA(X)_m wherein m = 1-3, preferably m = 2 or 3; X is a hydrolyzable group, preferably X is an alkoxy group OR₄ wherein R₄ is a linear or branched C1-C5 alkyl radical; R₃ and A are as above, preferably A is an atom selected between Si or Ti; when A is Si preferably m = 3 and R3 is methyl or ethyl.

13. Cables according to claim 12, wherein the dispersing agents are selected from one or more of the following: vinyltriethoxysilane, 3-aminopropyltriethoxysilane, 3-chloroisobutyltriethoxysilane, 3-mercaptopropyltriethoxysilane, octyltriethoxy- silane, diisopropoxytitanium bisacetylacetonate.

14. Cables according to claims 1-13, wherein component (B) is the zinc oxide and/or zinc borate optionally treated with dispersing agent and mixtures thereof.

15. Cables according to claims 1-14, wherein component (C) is selected from fillers, preferably polytetrafluoroethylene (PTFE) and silicates, more preferably PTFE; pigments, preferably iron, chromium oxides; thermal stabilizers, preferably hindered phenols, more preferably Irganox^® 1010, Mark-260^®; organic acid scavengers, preferably oligomers of acrylic acid/ethylene partially salified with alkaline metal ions (Aclyn-316^®); and wherein the amount of component (C) is between 0 and 10% by weight based on the total of the composition.

16. Cables according to claims 1-15, wherein the polymeric compositions comprise the preferred components of (A), (B), (C).

17. Cables according to claims 1-16, wherein the perfluoropolymer of the primary cables is a thermoprocessable semicrystlline copolymer having a second melting temperature higher than 200°C, preferably higher than 230°C, more preferably higher than 260°C.

18. Cables according to claim 17, wherein the perfluoro-polymers are selected from the following classes:

(i) thermoprocessable semicrystalline copolymers of TFE with HFP, wherein preferably HFP is between 2.8 and 20% by weight; optionally containing monomeric units deriving from one or more perfluoroalkylvinylethers (PAVE) CF₂=CF-O-Rf wherein R_f is a C_rC₆ perfluoroalkyl group, preferably perfluoromethylvinylether (PMVE), perfluoroethylvinylether (PEVE) and perfluoropropylvinylether (PPVE); more preferably HFP is between 9 and 17% by weight and PAVE 0.2-5.5% by weight; among PAVEs the perfluoroethylvinylether (PEVE) is preferred;

(ii) thermoplastic semicrystalline copolymers of TFE with perfluoroalkyl- vinylethers (PAVE) CF₂=CF-O-Rf wherein R_f is a C_rC₆ perfluoroalkyl group, preferably perfluoromethylvinylether, perfluoroethylvinylether and perfluoropropylvinylether wherein the total PAVE amount ranges from 1 to 20% by weight, preferably from 2 to 15%; said copolymers are preferably selected from TFE copolymers containing from 0.5 to 13% of PMVE and from 0.5 to 3% by weight of PPVE or PEVE; optionally containing monomeric units deriving from HFP in amounts between 2.8 and 20% by weight when PAVE is higher than 5.5% by weight; or they optionally contain HFP in amounts between 0.1 and 2.8% by weight when PAVE is lower than 5.5% by weight;

(iii) thermoprocessable copolymers of tetrafluoroethylene (TFE) comprising: (a1) from 0.1 to 15% by moles, preferably from 0.5 to 9%, of a fluorodioxole of formula: CZ=C-Ta

O O (I)

\ /

(b1) from 0 to 15%, preferably from 0 to 10%, by moles of a perfluorinated monomer selected from hexafluoropropene (HFP) and perfluoroalkylvinylethers of formula CF₂=CF-ORV, wherein R'f is a C₂-C₄ perfluoroalkyl, or mixtures thereof;

(c1) TFE being the remaining part to 100% by moles; wherein the amount of monomers (a1) +(b1) is lower than or equal to 20% by moles, preferably lower than or equal to 12% by moles.

19. Cables according to claims 1-18, wherein the jacket composition has a melt flow index higher than 7 g/10 min, measured at 275°C according to ASTM D 1238.