Stress/Thermal Cracking Resistant Cable Sheath Material
A composition useful as a wire or cable insulation or sheathing layer, the composition comprising (i) an inorganic flame retardant, e.g., aluminum trihydroxide (ATH), (ii) ethylene ethyl acetate (EEA) or ethylene butyl acrylate (EBA), (iii) a homogeneous polyethylene, (iv) an ethylenic resin modified with an organo-functional group, e.g., maleic anhydride (MAH) grafted polyethylene, (v) a silicone polymer, and optionally, (vi) a smoke suppressant. The insulation or sheathing layer comprising the composition of this invention exhibits good resistance to stress and/or thermal cracking.
1 . A composition comprising:
(A) 15 to 25 wt % of at least one of EEA and EBA;
(B) 5 to 15 wt % of a homogeneous polyethylene;
(C) 3 to 12 wt % of an ethylenic resin modified with a compound or compounds containing an organo-functional group;
(D) 40 to 65 wt % of a non-halogenated flame retardant; and
(E) 1 to 8 wt % of a silicone polymer.
2 . (canceled)
3 . The composition of claim 1 in which the homogeneous polyethylene comprises units derived from a C 3-12 α-olefin.
4 - 5 . (canceled)
6 . The composition of claim 1 in which the functional group of the ethylenic resin (C) is a unit derived from maleic anhydride.
7 - 8 . (canceled)
9 . The composition of claim 1 in which the non-halogenated flame retardant is at least one of ATH, red phosphorous, silica, alumina, titanium oxide, carbon nanotubes, talc, clay, organo-modified clay, calcium carbonate, zinc borate, antimony trioxide, wollastonite, mica, ammonium octamolybdate, frits, hollow glass microspheres, intumescent compounds and expanded graphite.
10 . The composition of claim 1 in which the non-halogenated flame retardant is ATH.
11 - 15 . (canceled)
16 . The composition of claim 1 in which the silicone polymer is of the formula:
R—Si—O—(RSiO) n —R—Si—O—R
in which each R is independently a saturated or unsaturated alkyl group, an aryl group, or a hydrogen atom, and n is a number of 1 to 5000.
17 . The composition of claim 1 in which the silicone polymer is at least one of glycidyl-modified silicate, amino-modified silicate, mercapto-modified silicate, polyether-modified silicate, carboxylic acid modified silicate, or higher fatty acid modified silicate.
18 . The composition of claim 1 in which the silicone polymer has a viscosity greater than 5,000,000 centistokes at 23 C.
19 . The composition of claim 1 in which the silicone polymer is an ultra-high molecular weight polydimethylsiloxane.
20 . The composition of claim 1 in which a smoke suppressant is present in an amount of 1 to 20 wt %.
21 . The composition of claim 20 in which the smoke suppressant is at least one of magnesium hydroxide, zinc borate, a magnesium/zinc/antimony complex, a magnesium/zinc complex and an anhydrous sodium antimonate.
22 . (canceled)
23 . The composition of claim 1 in which the EEA and/or EBA comprises between 18 and 21 wt % based on the weight of the composition.
24 . The composition of claim 23 in which the homogeneous polyethylene comprises between 8 and 12 wt % based on the weight of the composition.
25 . The composition of claim 24 in which the modified ethylenic resin (C) comprises between 5 and 8 wt % based on the weight of the composition.
26 . The composition of claim 25 in which the non-halogenated flame retardant comprises between 50 and 55 wt % based on the weight of the composition.
27 . The composition of claim 26 in which the silicone polymer comprises between 3 and 6 wt % based on the weight of the composition.
28 . (canceled)
29 . A cable insulation layer comprising the composition of claim 1 .
30 . A cable protective outer jacket comprising the composition of claim 1 .
31 . A cable core sheath comprising the composition of claim 1 .
32 . A cable comprising one or more electrical conductors or communications media, or a core of two or more electrical conductors or communications media, at least one of the electrical conductor, communications medium, or core being surrounded by a sheath comprising the composition of claim 1 .