Filled communication cable employing a paraffinic oil-base filling compound

Petrolatum-based filling compounds are known to migrate into the insulation and jacket of telephone cables and to extract the stabilizers, and as a consequence, to affect the physical and/or electrical characteristics of those cable components. It does not seem possible to avoid these characteristics of petrolatum in commercial compounding operations. The filling compound of this specification is for use in telephone cables and is based on better resistance to dripping at elevated temperatures, compatibility with high density polyethylene insulation and low density and medium density polyethylene jacket compounds. It has processability at moderate elevated temperatures, resistance to cracking at room temperature and low temperatures, adhesiveness and desirable electric properties.

BACKGROUND AND SUMMARY OF THE INVENTION 
The petrolatum used in the preparation of a filling compound is already a 
semisolid at room temperature and as such requires only a relatively 
slight modification to be converted into a material for filling air spaces 
in the telephone cables as conventionally manufactured. This invention 
provides an improved filling compound that is more compatible with the 
conventional plastic insulation of the conductors in filled telephone 
cables than a petrolatum-based filling compound. 
The filling compound of this specification uses a paraffinic type oil 
blended with amorphous polypropylene, wax and polyethylene with an 
antioxidant. The characteristics of these added ingredients will be 
explained in the detailed description. 
Other objects, features and advantages of the invention will appear or be 
pointed our at the description proceeds.

DESCRIPTION OF PREFERRED EMBODIMENT 
The drawing shows individual insulated conductors 10 assembled in a 
generally circular cross-section which forms the core 12 of the cable. 
These insulated conductors 10 may be bound together in a conventional way 
by a binder 13 of plastic tape, and the core is surrounded by a metal 
shield 14, preferably aluminum, shown as a tape folded longitudinally 
around the core with a longitudinally extending lap seam 16. This shield 
14 is preferably aluminum foil; which may be copolymer protected as in 
U.S. Pat. Nos. 3,206,541 and 3,629,489 and it is covered by a protecting 
jacket 18 made of polyethylene, polyvinyl chloride or other suitable 
jacketing material. Insulation 19 on the conductors 10 is preferably 
polyethylene. 
Since the conductors 10 are of round cross-section, there is space between 
the conductors where they are not tangent to one another; and this space 
contains the filler 20 of the present invention. It will be understood 
that the core 12 is filled with the conductors 10 and that the filler 20 
permeates all spaces within the core which is not occupied by the 
insulated conductors 10. 
The filler material 20 must be flexible and should be tacky so as to adhere 
to the insulation jackets around the conductors and to itself. It must 
also remain flexible at the lowest temperature to which the cable will be 
subject when put to its intended use. 
The drip point must be high enough so that the filler 20 will not leak out 
of the core at any location where there may be a break in the shield 14 or 
a leak at the seam 16 or clearance at terminations or splices where liquid 
within the cable could run out. 
The filler of this invention retains its flexibility so as to pass the 
standardized bend test at temperatures of about -36 to -40 degrees C. The 
tacky characteristics of the filler are retained at these bend temperature 
tests. The drip point of the filler is from about 85 degrees C. to about 
110.degree., depending upon the compounding. 
In the examples which follow, the ingredients will be identified by the 
symbols used in the test procedures, and further identification of the 
ingredients will follow the description of the results obtained by various 
formulations. 
Example A used 100 parts of paraffinic oil (2280); 50 parts of amorphous 
polypropylene (M-5K); 5 parts of Rosswax (RW-140) and 5 parts of Fisher 
Tropsch wax. This filler had a drip point of 95.degree. to 100.degree. C. 
and satisfactory low temperature bend test at -40.degree. C. 
Example B: In this example, the amount of wax used was cut in half by 
omitting the Rosswax and substituting for it 10 parts of low molecular 
weight polyethylene. This change raised the drip point to 
100.degree.-105.degree. C. and the low temperature bend remained at 
-40.degree. C. 
Example C: In this example, the compounding was the same as in Example B, 
except that the number of parts of polyethylene were reduced from 10 to 8 
and an antioxidant Irganox 1010 was added in an amount of 0.2 parts. The 
drip point was reduced 5.degree. C., and the low temperature bend test was 
-36.degree. C. instead of -40.degree.. 
Example D used a different paraffinic oil Sunflex 3340 of 100 parts, and 
amorphous polypropylene (M-5K) of 40 parts. The total amount of wax used 
was the same as in Example A but in slightly different proportions, 4 
parts wax Rosswax 140 and 6 parts of Fisher Tropsch wax. No polyethylene 
was used, but 0.2 parts of antioxidant Irganox 1010 was used in the 
formulation. The drip point was 80.degree. to 85.degree. C.; the low 
temperature bend test was -40.degree. C. 
Example E used the same amount of oil and amorphous polypropylene as in 
Example D, but no wax was used and no polyethylene. The antioxidant 
Irganox 1010 was retained. The drip point was the same as in Example D, 
but the low temperature bend test was-36.degree. C. instead of 
-40.degree.. 
Example F substituted a different oil Sunpar 2280 for the Sunflex 3340 of 
Example E, but retained the same amount (100 parts), and retained the same 
amount of amorphous polypropylene and antioxidant. The drip point remained 
the same at 85.degree. C; but the low temperature bend was reduced from 
-36.degree. to -40.degree. C. 
Example G used the same oil as in Example F but reduced the amount of 
amorphous polypropylene from 40 to 30 parts; and included wax in the 
mixture. 8 parts of wax Rosswax 140 were used with 2 parts of Fisher 
Tropsch. The same amount of antioxidant was used as in Example F. This 
change raised the drip point from 85.degree. to 100.degree. C., and the 
low temperature bend remained at -40.degree. C. 
Example H used the same ingredients as Example G but a different amorphous 
polypropylene was used (M-5W). The drip point was raised 5.degree. C., and 
the low temperature bend was -40.degree. C. 
Example I used the same formulation as Example H except that the 10 parts 
of wax were made up of only one kind of wax, Rosswax 140, and this change 
raised the drip point to a temperature in excess of 110.degree. C. with 
the low temperature bend still at -40.degree. C. 
Other tests were made using the same formulation as Example I but using 5 
parts of low molecular weight polyethylene and different waxes: Fischer 
Tropsch, Melkon and XFQ Cardipol LP; but while the viscosity and tacky 
characteristics remained satisfactory, no higher drip point could be 
obtained than with Examples H and I. 
The paraffinic oil Sunpar 2280 has a SUS viscosity of about 2500 at 
100.degree. F. and a pour point of about -15.degree. C. The paraffinic oil 
Sunflex 3340 has an SUS voscosity of about 3500 at 100.degree. F. and a 
pour point of about -15.degree. C. Both Sunpar 2280 and Sunflex 3340 may 
be obtained from the Sun Oil Co. located at Tulsa, Oklahoma. The amorphous 
polypropylenes M-5K and M-5W were procured from Eastman Chemical Products 
located at Kingsport, Tennessee. 
Rosswax 140 is a synthetic wax made by Frank B Ross Co., Inc. of Jersey 
City, New Jersey. Melkon a microcrystalline wax, Fischer Tropsch, a 
synthetic wax and XFQ Cardipol LP a polyolefin wax, were obtained from 
Western Petro Chemical of Chanute, Kansas. The low molecular weight 
polyethylene NA-250 was obtained from U.S. Industrial Chemical of 
Pittsburgh, Pa. The antioxidant Irganox 1010 can be obtained from 
Ciba-Geigy of Ardsley, New Jersey. 
Preferred embodiments of the invention have been described, but changes and 
modifications can be made and the equivalent materials substituted without 
departing from the invention as defined in the claims.