Telephone service wire with ester-based filling compound

This telephone service wire has metal conductors insulated with polyethylene plastic insulation or equivalent, assembled in a core having a flame-retardant polyvinyl chloride jacket. Space between the individual insulated conductors is filled with an improved filling compound for preventing access of water into the core of the service wire. The filler compound is an ester-based compound that avoids the disadvantages of the usual petrolatum-based filler compound which extracts not only antioxidants and copper-inhibitors from a polyethylene component but plasticizers from a polyvinyl chloride compound. Depletion of these essential compounding materials can seriously affect the physical characteristics of either the insulation or jacket of such filled telephone service wires.

BACKGROUND AND SUMMARY OF THE INVENTION 
What is needed is a filler compound that is compatible with both 
polyethylene and polyvinyl chloride compounds. Filled service wire 
requires a flame-retardant polyvinyl chloride jacket. The new filler 
compound of this specification is based on a plasticizer system that is 
commonly used in the manufacture of flame-retardant polyvinyl chloride 
compounds. This filling compound is designed primarily for use in a high 
density polyethylene insulated and polyvinyl chloride jacketed buried 
telephone service wire, and is based on the retention of the physical 
properties of polyethylene insulation and polyvinyl chloride jacket 
compounds after immersion in the filler compound at elevated temperatures, 
fluidity at the accepted processing temperature of 121.degree. C., 
resistance to dripping at elevated temperatures, commonly referred to as 
the "drip point," and adhesiveness to cable components and resistance to 
cracking at room and lower temperature. 
Other objects, features and advantages of the invention will appear or be 
pointed out as the description proceeds.

DESCRIPTION OF PREFERRED EMBODIMENT 
The filler compound of this specification includes one or more esters 
compounded with wax and polyethylene or chlorinated polyethylene. 
Amorphous polypropylene is used with some of the examples. Limited amounts 
of petrolatum are used with most of the preferred embodiments in amounts 
up to about 25% of the filler. The petrolatum is solidified with a low 
density polyethylene. 
In each of the formulations given as examples of the filler of this 
specification, the ingredients will be identified by their laboratory 
designations, and more specific identification, and source for the items 
will follow the examples. 
EXAMPLE I 
This example is a formulation of 60 parts of (DIDP) ester plasticizer; 40 
parts of (TINTM), another ester plasticizer 12 parts of chlorinated 
polyethylene; 10 parts of another wax (XFQ); 16 parts amorphous 
polypropylene; and these ingredients are blended into about 40 parts of 
petrolatum. After thorough mixing with the 40 parts of petrolatum, the 
filler had a drip point of 80.degree. to 85.degree. C. and withstood the 
standard low temperature bend test without cracking at -44.degree. C. 
DIDP is diisodecyl phthalate, and TINTM is tri-iso-nonyl-trimellitate. 
These ingredients are made by Exxon Chemicals of Houston, Tex. The wax XFQ 
is a polyolefin was available from Western Petro Chemical of Chanute, 
Kans. and chlorinated polyethylene from Dow Chemical of Baton Rouge, La. 
EXAMPLE II 
The filler of this example was made with 80 parts of ester plasticizer 
(DOP) and 20 parts of ester plasticizer (TINTM); 10 parts of polyolefin 
wax (XFQ); 20 parts of amorphous polypropylene; 5 parts of polyethylene; 
and 40 parts of "Q-9" which consists of approximately 89.8 parts of 
petrolatum; 9 parts of low density polyethylene; 1 part of butyl rubber; 
and 0.2 parts of antioxidant. This Q-9 formulation is available from the 
Witco Chemical Corporation of Petrolia, Pa. The DOP is available from 
Exxon Chemicals. The amorphous polypropylene was obtained from Eastman 
Chemical Products in Kingsport, Tenn. 
EXAMPLE III 
This example uses the same amount of ester plasticizers as in Example I but 
in somewhat different proportions; i.e., 66 parts of DIDP and 34 parts of 
TINTM. 5 parts of chlorinated polyethylene was used, and 5 parts of the 
wax XFQ. The formulation also contains 5 parts of amorphous polypropylene, 
5 parts of polyethylene and 5 parts of polyvinyl chloride. Minor 
ingredients included one part each of materials designated in the 
laboratory notes as "224" and "517." These ingredients are Mark 224, an 
epoxy stabilizer for PVC, and Mark 517, a phosphite stabilizer also for 
PVC. Both stabilizers were obtained from Argus Chemicals of Brooklyn, N.Y. 
The polyvinyl chloride was obtained from Tenneco Chemical of Burlington, 
N.J. 
Example III had a drip point of 110.degree. C., 5.degree. higher than 
Example II, and about 25.degree. higher than Example I. The low 
temperature bend test did not crack at -40.degree. C., which was a few 
degrees higher than the bend test for Example II. 
EXAMPLE IV 
In this example, 90 parts of polybutene were added to the formulation, and 
the ingredients of Example III were used but with an increase in the XFQ 
wax from 5 to 19 parts and an increase in the amorphous polypropylene from 
5 to 18 parts. The drip point remained at 110.degree. C., and the low 
temperature bend test was satisfactory at -40.degree. C. 
EXAMPLE V 
In this example, 100 parts of TINTM ester plasticizer was used but no other 
ester plasticizers were used. 8 parts of chlorinated polyethylene were 
used and 10 parts of the wax XFQ. 3.6 parts of amorphous polypropylene 
were used in this example, and 35.8 parts of the petrolatum Q-9. The drip 
point was reduced to 80.degree. C., but the low bend test was still 
satisfactory at -40.degree. C. 
EXAMPLE VI 
This example differed from Example V in that the amorphous polypropylene 
was omitted, and the Q-9 was increased to 39 parts. The drip point was 
somewhat lower than any of the other examples, but the low temperature 
bend test was satisfactory at -45.5.degree. C. Thus the formulation of 
Example VI was not as good as the other examples at the high temperature 
conditions under which the cable might be used but was better at the low 
temperature environments. 
All of the above examples were satisfactory filling compounds for the 
telephone service cable. Their ingredients were compatible with the 
polyvinyl chloride jacket. In those formulations where Q-9 petrolatum was 
used (Examples I, V and VI), there was not enough petrolatum to extract 
the plasticizers from the PVC compound of the cable jacket. 
The drawing is a sectional view through a telephone service cable which is 
made with insulated conductors 10 crowded together in a core 11 and 
surrounded by a plastic jacket 12 of polyvinyl chloride, polyethylene or 
other suitable jacketing material. Such telephone service cables are 
commonly made with and without metal armor 14 surrounding the group of 
insulated conductors 10. The spaces around the insulated conductors 10 and 
within the inner jacket 12 are filled with the ester-based filling 
compound of this specification. In an armored construction, an outer 
plastic jacket 28, which is preferably polyvinyl chloride or an equivalent 
plastic composition which resists abrasion, surrounds the armor 14, and 
any clearance between the armor 14 and the outer jacket 28 is filled with 
the ester-based filler composition 20. 
The insulated conductors 10 touch adjacent insulated conductors 10 at 
points of tangency. The insulation of conductors 10 is indicated by the 
reference characters 30, and the space between the insulated conductors, 
where they do not touch other conductors, is filled with the filler 
composition 20 of this specification. The drawing shows a cable with two 
jackets but the filler can be used also with cables having only one 
jacket. 
All of the examples of the filler material described in this specification 
have adhesive qualities which cause them to adhere to the insulation of 
the conductors 10; and this adhesion also holds the material of the filler 
together. The adhesion is maintained over the full temperature range from 
the drip point down to the lowest temperature for which the filler is 
intended to be used. Ordinarily, this temperature is -40.degree. C. and 
commercial standards require that telephone service cables have the 
flexibility to be bent under installation conditions without having the 
cable or the filler material crack at the region of bending. 
Preferred embodiments of this invention have been described in detail, but 
changes and modifications may be made in the filler formulation without 
departing from the invention as defined in the claims.