Filled cables

DETAILED DESCRIPTION The cable of the present invention is an improvement over the cable disclosed in U.
S.
Pat.
No.
4,259,540 in that it retains all the positive attributes of the prior art cable and yet in addition, has capacitance stability and high temperature flow resistance which are required for aerial use, and further does not exhibit oil separation.
In addition, the filling compound for waterproofing of the novel cable is easily injected into the cable.
The filling compound of the novel cable employs a styrene-rubber diblock copolymer to replace all or part of the styrene-rubber-styrene triblock copolymer cited in the '540 patent which is incorporated herein by reference.
Applicant has discovered that the prior art rubber, which is capped on both ends by styrene, has a higher physical crosslink density than the styrene-rubber diblock copolymer used in the filling composition of the present invention wherein the rubber has a styrene cap on one end only.
The crosslinks are physical in nature and result from separate styrene and rubber block domains which form due to the inherent incompatibility of the two types of blocks.
Inasmuch as the styrene blocks are rigid below their Tg of approximately 90.
degree.
C.
, they act as physical crosslinks below the styrene Tg where the styrene block is on both ends of the molecule (triblock).
Applicant has discovered that this lower physical crosslink density results in the oil, which is incorporated in the composition, to be more effectively gelled.
Accordingly, syneresis (separation) and cell filling are significantly reduced or eliminated.
Further, one may select a styrene-rubber diblock copolymer which is approximately half the molecular weight of the prior styrene-rubber-styrene copolymer, but yet having approximately e same styrene block to rubber block ratio.
T is results in a lower viscosity material which makes it possible to add polybutene oil and polyethylene wax to the filling composition to aid in preventing insulation cell filling and in improving high temperature flow characteristics